1<html> 2<head> 3<title>pcre2api specification</title> 4</head> 5<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6<h1>pcre2api man page</h1> 7<p> 8Return to the <a href="index.html">PCRE2 index page</a>. 9</p> 10<p> 11This page is part of the PCRE2 HTML documentation. It was generated 12automatically from the original man page. If there is any nonsense in it, 13please consult the man page, in case the conversion went wrong. 14<br> 15<ul> 16<li><a name="TOC1" href="#SEC1">PCRE2 NATIVE API BASIC FUNCTIONS</a> 17<li><a name="TOC2" href="#SEC2">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a> 18<li><a name="TOC3" href="#SEC3">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a> 19<li><a name="TOC4" href="#SEC4">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a> 20<li><a name="TOC5" href="#SEC5">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a> 21<li><a name="TOC6" href="#SEC6">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a> 22<li><a name="TOC7" href="#SEC7">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a> 23<li><a name="TOC8" href="#SEC8">PCRE2 NATIVE API JIT FUNCTIONS</a> 24<li><a name="TOC9" href="#SEC9">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a> 25<li><a name="TOC10" href="#SEC10">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a> 26<li><a name="TOC11" href="#SEC11">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a> 27<li><a name="TOC12" href="#SEC12">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a> 28<li><a name="TOC13" href="#SEC13">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a> 29<li><a name="TOC14" href="#SEC14">PCRE2 API OVERVIEW</a> 30<li><a name="TOC15" href="#SEC15">STRING LENGTHS AND OFFSETS</a> 31<li><a name="TOC16" href="#SEC16">NEWLINES</a> 32<li><a name="TOC17" href="#SEC17">MULTITHREADING</a> 33<li><a name="TOC18" href="#SEC18">PCRE2 CONTEXTS</a> 34<li><a name="TOC19" href="#SEC19">CHECKING BUILD-TIME OPTIONS</a> 35<li><a name="TOC20" href="#SEC20">COMPILING A PATTERN</a> 36<li><a name="TOC21" href="#SEC21">JUST-IN-TIME (JIT) COMPILATION</a> 37<li><a name="TOC22" href="#SEC22">LOCALE SUPPORT</a> 38<li><a name="TOC23" href="#SEC23">INFORMATION ABOUT A COMPILED PATTERN</a> 39<li><a name="TOC24" href="#SEC24">INFORMATION ABOUT A PATTERN'S CALLOUTS</a> 40<li><a name="TOC25" href="#SEC25">SERIALIZATION AND PRECOMPILING</a> 41<li><a name="TOC26" href="#SEC26">THE MATCH DATA BLOCK</a> 42<li><a name="TOC27" href="#SEC27">MEMORY USE FOR MATCH DATA BLOCKS</a> 43<li><a name="TOC28" href="#SEC28">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a> 44<li><a name="TOC29" href="#SEC29">NEWLINE HANDLING WHEN MATCHING</a> 45<li><a name="TOC30" href="#SEC30">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a> 46<li><a name="TOC31" href="#SEC31">OTHER INFORMATION ABOUT A MATCH</a> 47<li><a name="TOC32" href="#SEC32">ERROR RETURNS FROM <b>pcre2_match()</b></a> 48<li><a name="TOC33" href="#SEC33">OBTAINING A TEXTUAL ERROR MESSAGE</a> 49<li><a name="TOC34" href="#SEC34">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> 50<li><a name="TOC35" href="#SEC35">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a> 51<li><a name="TOC36" href="#SEC36">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> 52<li><a name="TOC37" href="#SEC37">CREATING A NEW STRING WITH SUBSTITUTIONS</a> 53<li><a name="TOC38" href="#SEC38">DUPLICATE CAPTURE GROUP NAMES</a> 54<li><a name="TOC39" href="#SEC39">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a> 55<li><a name="TOC40" href="#SEC40">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a> 56<li><a name="TOC41" href="#SEC41">SEE ALSO</a> 57<li><a name="TOC42" href="#SEC42">AUTHOR</a> 58<li><a name="TOC43" href="#SEC43">REVISION</a> 59</ul> 60<P> 61<b>#include <pcre2.h></b> 62<br> 63<br> 64PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a 65description of all its native functions. See the 66<a href="pcre2.html"><b>pcre2</b></a> 67document for an overview of all the PCRE2 documentation. 68</P> 69<br><a name="SEC1" href="#TOC1">PCRE2 NATIVE API BASIC FUNCTIONS</a><br> 70<P> 71<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 72<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 73<b> pcre2_compile_context *<i>ccontext</i>);</b> 74<br> 75<br> 76<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 77<br> 78<br> 79<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 80<b> pcre2_general_context *<i>gcontext</i>);</b> 81<br> 82<br> 83<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 84<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 85<br> 86<br> 87<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 88<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 89<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 90<b> pcre2_match_context *<i>mcontext</i>);</b> 91<br> 92<br> 93<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 94<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 95<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 96<b> pcre2_match_context *<i>mcontext</i>,</b> 97<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 98<br> 99<br> 100<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 101</P> 102<br><a name="SEC2" href="#TOC1">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a><br> 103<P> 104<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 105<br> 106<br> 107<b>PCRE2_SIZE pcre2_get_match_data_size(pcre2_match_data *<i>match_data</i>);</b> 108<br> 109<br> 110<b>PCRE2_SIZE pcre2_get_match_data_heapframes_size(</b> 111<b> pcre2_match_data *<i>match_data</i>);</b> 112<br> 113<br> 114<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 115<br> 116<br> 117<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 118<br> 119<br> 120<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 121</P> 122<br><a name="SEC3" href="#TOC1">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a><br> 123<P> 124<b>pcre2_general_context *pcre2_general_context_create(</b> 125<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 126<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 127<br> 128<br> 129<b>pcre2_general_context *pcre2_general_context_copy(</b> 130<b> pcre2_general_context *<i>gcontext</i>);</b> 131<br> 132<br> 133<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 134</P> 135<br><a name="SEC4" href="#TOC1">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a><br> 136<P> 137<b>pcre2_compile_context *pcre2_compile_context_create(</b> 138<b> pcre2_general_context *<i>gcontext</i>);</b> 139<br> 140<br> 141<b>pcre2_compile_context *pcre2_compile_context_copy(</b> 142<b> pcre2_compile_context *<i>ccontext</i>);</b> 143<br> 144<br> 145<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 146<br> 147<br> 148<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 149<b> uint32_t <i>value</i>);</b> 150<br> 151<br> 152<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 153<b> const uint8_t *<i>tables</i>);</b> 154<br> 155<br> 156<b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 157<b> uint32_t <i>extra_options</i>);</b> 158<br> 159<br> 160<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 161<b> PCRE2_SIZE <i>value</i>);</b> 162<br> 163<br> 164<b>int pcre2_set_max_pattern_compiled_length(</b> 165<b> pcre2_compile_context *<i>ccontext</i>, PCRE2_SIZE <i>value</i>);</b> 166<br> 167<br> 168<b>int pcre2_set_max_varlookbehind(pcre2_compile_contest *<i>ccontext</i>,</b> 169<b>" uint32_t <i>value</i>);</b> 170<br> 171<br> 172<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 173<b> uint32_t <i>value</i>);</b> 174<br> 175<br> 176<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 177<b> uint32_t <i>value</i>);</b> 178<br> 179<br> 180<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 181<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 182</P> 183<br><a name="SEC5" href="#TOC1">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a><br> 184<P> 185<b>pcre2_match_context *pcre2_match_context_create(</b> 186<b> pcre2_general_context *<i>gcontext</i>);</b> 187<br> 188<br> 189<b>pcre2_match_context *pcre2_match_context_copy(</b> 190<b> pcre2_match_context *<i>mcontext</i>);</b> 191<br> 192<br> 193<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 194<br> 195<br> 196<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 197<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 198<b> void *<i>callout_data</i>);</b> 199<br> 200<br> 201<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 202<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 203<b> void *<i>callout_data</i>);</b> 204<br> 205<br> 206<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 207<b> PCRE2_SIZE <i>value</i>);</b> 208<br> 209<br> 210<b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 211<b> uint32_t <i>value</i>);</b> 212<br> 213<br> 214<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 215<b> uint32_t <i>value</i>);</b> 216<br> 217<br> 218<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 219<b> uint32_t <i>value</i>);</b> 220</P> 221<br><a name="SEC6" href="#TOC1">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a><br> 222<P> 223<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 224<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 225<br> 226<br> 227<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 228<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 229<b> PCRE2_SIZE *<i>bufflen</i>);</b> 230<br> 231<br> 232<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 233<br> 234<br> 235<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 236<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 237<br> 238<br> 239<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 240<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 241<b> PCRE2_SIZE *<i>bufflen</i>);</b> 242<br> 243<br> 244<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 245<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 246<br> 247<br> 248<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 249<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 250<br> 251<br> 252<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 253<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 254<br> 255<br> 256<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 257<b> PCRE2_SPTR <i>name</i>);</b> 258<br> 259<br> 260<b>void pcre2_substring_list_free(PCRE2_UCHAR **<i>list</i>);</b> 261<br> 262<br> 263<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 264<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 265</P> 266<br><a name="SEC7" href="#TOC1">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a><br> 267<P> 268<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 269<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 270<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 271<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacementz</i>,</b> 272<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 273<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 274</P> 275<br><a name="SEC8" href="#TOC1">PCRE2 NATIVE API JIT FUNCTIONS</a><br> 276<P> 277<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 278<br> 279<br> 280<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 281<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 282<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 283<b> pcre2_match_context *<i>mcontext</i>);</b> 284<br> 285<br> 286<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 287<br> 288<br> 289<b>pcre2_jit_stack *pcre2_jit_stack_create(size_t <i>startsize</i>,</b> 290<b> size_t <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 291<br> 292<br> 293<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 294<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 295<br> 296<br> 297<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 298</P> 299<br><a name="SEC9" href="#TOC1">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a><br> 300<P> 301<b>int32_t pcre2_serialize_decode(pcre2_code **<i>codes</i>,</b> 302<b> int32_t <i>number_of_codes</i>, const uint8_t *<i>bytes</i>,</b> 303<b> pcre2_general_context *<i>gcontext</i>);</b> 304<br> 305<br> 306<b>int32_t pcre2_serialize_encode(const pcre2_code **<i>codes</i>,</b> 307<b> int32_t <i>number_of_codes</i>, uint8_t **<i>serialized_bytes</i>,</b> 308<b> PCRE2_SIZE *<i>serialized_size</i>, pcre2_general_context *<i>gcontext</i>);</b> 309<br> 310<br> 311<b>void pcre2_serialize_free(uint8_t *<i>bytes</i>);</b> 312<br> 313<br> 314<b>int32_t pcre2_serialize_get_number_of_codes(const uint8_t *<i>bytes</i>);</b> 315</P> 316<br><a name="SEC10" href="#TOC1">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a><br> 317<P> 318<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 319<br> 320<br> 321<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 322<br> 323<br> 324<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 325<b> PCRE2_SIZE <i>bufflen</i>);</b> 326<br> 327<br> 328<b>const uint8_t *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 329<br> 330<br> 331<b>void pcre2_maketables_free(pcre2_general_context *<i>gcontext</i>,</b> 332<b> const uint8_t *<i>tables</i>);</b> 333<br> 334<br> 335<b>int pcre2_pattern_info(const pcre2_code *<i>code</i>, uint32_t <i>what</i>,</b> 336<b> void *<i>where</i>);</b> 337<br> 338<br> 339<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 340<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 341<b> void *<i>user_data</i>);</b> 342<br> 343<br> 344<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 345</P> 346<br><a name="SEC11" href="#TOC1">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a><br> 347<P> 348<b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b> 349<b> uint32_t <i>value</i>);</b> 350<br> 351<br> 352<b>int pcre2_set_recursion_memory_management(</b> 353<b> pcre2_match_context *<i>mcontext</i>,</b> 354<b> void *(*<i>private_malloc</i>)(size_t, void *),</b> 355<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 356<br> 357<br> 358These functions became obsolete at release 10.30 and are retained only for 359backward compatibility. They should not be used in new code. The first is 360replaced by <b>pcre2_set_depth_limit()</b>; the second is no longer needed and 361has no effect (it always returns zero). 362</P> 363<br><a name="SEC12" href="#TOC1">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a><br> 364<P> 365<b>pcre2_convert_context *pcre2_convert_context_create(</b> 366<b> pcre2_general_context *<i>gcontext</i>);</b> 367<br> 368<br> 369<b>pcre2_convert_context *pcre2_convert_context_copy(</b> 370<b> pcre2_convert_context *<i>cvcontext</i>);</b> 371<br> 372<br> 373<b>void pcre2_convert_context_free(pcre2_convert_context *<i>cvcontext</i>);</b> 374<br> 375<br> 376<b>int pcre2_set_glob_escape(pcre2_convert_context *<i>cvcontext</i>,</b> 377<b> uint32_t <i>escape_char</i>);</b> 378<br> 379<br> 380<b>int pcre2_set_glob_separator(pcre2_convert_context *<i>cvcontext</i>,</b> 381<b> uint32_t <i>separator_char</i>);</b> 382<br> 383<br> 384<b>int pcre2_pattern_convert(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 385<b> uint32_t <i>options</i>, PCRE2_UCHAR **<i>buffer</i>,</b> 386<b> PCRE2_SIZE *<i>blength</i>, pcre2_convert_context *<i>cvcontext</i>);</b> 387<br> 388<br> 389<b>void pcre2_converted_pattern_free(PCRE2_UCHAR *<i>converted_pattern</i>);</b> 390<br> 391<br> 392These functions provide a way of converting non-PCRE2 patterns into 393patterns that can be processed by <b>pcre2_compile()</b>. This facility is 394experimental and may be changed in future releases. At present, "globs" and 395POSIX basic and extended patterns can be converted. Details are given in the 396<a href="pcre2convert.html"><b>pcre2convert</b></a> 397documentation. 398</P> 399<br><a name="SEC13" href="#TOC1">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> 400<P> 401There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code 402units, respectively. However, there is just one header file, <b>pcre2.h</b>. 403This contains the function prototypes and other definitions for all three 404libraries. One, two, or all three can be installed simultaneously. On Unix-like 405systems the libraries are called <b>libpcre2-8</b>, <b>libpcre2-16</b>, and 406<b>libpcre2-32</b>, and they can also co-exist with the original PCRE libraries. 407Every PCRE2 function comes in three different forms, one for each library, for 408example: 409<pre> 410 <b>pcre2_compile_8()</b> 411 <b>pcre2_compile_16()</b> 412 <b>pcre2_compile_32()</b> 413</pre> 414There are also three different sets of data types: 415<pre> 416 <b>PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32</b> 417 <b>PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32</b> 418</pre> 419The UCHAR types define unsigned code units of the appropriate widths. 420For example, PCRE2_UCHAR16 is usually defined as `uint16_t'. 421The SPTR types are pointers to constants of the equivalent UCHAR types, 422that is, they are pointers to vectors of unsigned code units. 423</P> 424<P> 425Character strings are passed to a PCRE2 library as sequences of unsigned 426integers in code units of the appropriate width. The length of a string may 427be given as a number of code units, or the string may be specified as 428zero-terminated. 429</P> 430<P> 431Many applications use only one code unit width. For their convenience, macros 432are defined whose names are the generic forms such as <b>pcre2_compile()</b> and 433PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to 434generate the appropriate width-specific function and macro names. 435PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it 436to be 8, 16, or 32 before including <b>pcre2.h</b> in order to make use of the 437generic names. 438</P> 439<P> 440Applications that use more than one code unit width can be linked with more 441than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before 442including <b>pcre2.h</b>, and then use the real function names. Any code that is 443to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is 444unknown should also use the real function names. (Unfortunately, it is not 445possible in C code to save and restore the value of a macro.) 446</P> 447<P> 448If PCRE2_CODE_UNIT_WIDTH is not defined before including <b>pcre2.h</b>, a 449compiler error occurs. 450</P> 451<P> 452When using multiple libraries in an application, you must take care when 453processing any particular pattern to use only functions from a single library. 454For example, if you want to run a match using a pattern that was compiled with 455<b>pcre2_compile_16()</b>, you must do so with <b>pcre2_match_16()</b>, not 456<b>pcre2_match_8()</b> or <b>pcre2_match_32()</b>. 457</P> 458<P> 459In the function summaries above, and in the rest of this document and other 460PCRE2 documents, functions and data types are described using their generic 461names, without the _8, _16, or _32 suffix. 462</P> 463<br><a name="SEC14" href="#TOC1">PCRE2 API OVERVIEW</a><br> 464<P> 465PCRE2 has its own native API, which is described in this document. There are 466also some wrapper functions for the 8-bit library that correspond to the 467POSIX regular expression API, but they do not give access to all the 468functionality of PCRE2 and they are not thread-safe. They are described in the 469<a href="pcre2posix.html"><b>pcre2posix</b></a> 470documentation. Both these APIs define a set of C function calls. 471</P> 472<P> 473The native API C data types, function prototypes, option values, and error 474codes are defined in the header file <b>pcre2.h</b>, which also contains 475definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers 476for the library. Applications can use these to include support for different 477releases of PCRE2. 478</P> 479<P> 480In a Windows environment, if you want to statically link an application program 481against a non-dll PCRE2 library, you must define PCRE2_STATIC before including 482<b>pcre2.h</b>. 483</P> 484<P> 485The functions <b>pcre2_compile()</b> and <b>pcre2_match()</b> are used for 486compiling and matching regular expressions in a Perl-compatible manner. A 487sample program that demonstrates the simplest way of using them is provided in 488the file called <i>pcre2demo.c</i> in the PCRE2 source distribution. A listing 489of this program is given in the 490<a href="pcre2demo.html"><b>pcre2demo</b></a> 491documentation, and the 492<a href="pcre2sample.html"><b>pcre2sample</b></a> 493documentation describes how to compile and run it. 494</P> 495<P> 496The compiling and matching functions recognize various options that are passed 497as bits in an options argument. There are also some more complicated parameters 498such as custom memory management functions and resource limits that are passed 499in "contexts" (which are just memory blocks, described below). Simple 500applications do not need to make use of contexts. 501</P> 502<P> 503Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be 504built in appropriate hardware environments. It greatly speeds up the matching 505performance of many patterns. Programs can request that it be used if 506available by calling <b>pcre2_jit_compile()</b> after a pattern has been 507successfully compiled by <b>pcre2_compile()</b>. This does nothing if JIT 508support is not available. 509</P> 510<P> 511More complicated programs might need to make use of the specialist functions 512<b>pcre2_jit_stack_create()</b>, <b>pcre2_jit_stack_free()</b>, and 513<b>pcre2_jit_stack_assign()</b> in order to control the JIT code's memory usage. 514</P> 515<P> 516JIT matching is automatically used by <b>pcre2_match()</b> if it is available, 517unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT 518matching, which gives improved performance at the expense of less sanity 519checking. The JIT-specific functions are discussed in the 520<a href="pcre2jit.html"><b>pcre2jit</b></a> 521documentation. 522</P> 523<P> 524A second matching function, <b>pcre2_dfa_match()</b>, which is not 525Perl-compatible, is also provided. This uses a different algorithm for the 526matching. The alternative algorithm finds all possible matches (at a given 527point in the subject), and scans the subject just once (unless there are 528lookaround assertions). However, this algorithm does not return captured 529substrings. A description of the two matching algorithms and their advantages 530and disadvantages is given in the 531<a href="pcre2matching.html"><b>pcre2matching</b></a> 532documentation. There is no JIT support for <b>pcre2_dfa_match()</b>. 533</P> 534<P> 535In addition to the main compiling and matching functions, there are convenience 536functions for extracting captured substrings from a subject string that has 537been matched by <b>pcre2_match()</b>. They are: 538<pre> 539 <b>pcre2_substring_copy_byname()</b> 540 <b>pcre2_substring_copy_bynumber()</b> 541 <b>pcre2_substring_get_byname()</b> 542 <b>pcre2_substring_get_bynumber()</b> 543 <b>pcre2_substring_list_get()</b> 544 <b>pcre2_substring_length_byname()</b> 545 <b>pcre2_substring_length_bynumber()</b> 546 <b>pcre2_substring_nametable_scan()</b> 547 <b>pcre2_substring_number_from_name()</b> 548</pre> 549<b>pcre2_substring_free()</b> and <b>pcre2_substring_list_free()</b> are also 550provided, to free memory used for extracted strings. If either of these 551functions is called with a NULL argument, the function returns immediately 552without doing anything. 553</P> 554<P> 555The function <b>pcre2_substitute()</b> can be called to match a pattern and 556return a copy of the subject string with substitutions for parts that were 557matched. 558</P> 559<P> 560Functions whose names begin with <b>pcre2_serialize_</b> are used for saving 561compiled patterns on disc or elsewhere, and reloading them later. 562</P> 563<P> 564Finally, there are functions for finding out information about a compiled 565pattern (<b>pcre2_pattern_info()</b>) and about the configuration with which 566PCRE2 was built (<b>pcre2_config()</b>). 567</P> 568<P> 569Functions with names ending with <b>_free()</b> are used for freeing memory 570blocks of various sorts. In all cases, if one of these functions is called with 571a NULL argument, it does nothing. 572</P> 573<br><a name="SEC15" href="#TOC1">STRING LENGTHS AND OFFSETS</a><br> 574<P> 575The PCRE2 API uses string lengths and offsets into strings of code units in 576several places. These values are always of type PCRE2_SIZE, which is an 577unsigned integer type, currently always defined as <i>size_t</i>. The largest 578value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved 579as a special indicator for zero-terminated strings and unset offsets. 580Therefore, the longest string that can be handled is one less than this 581maximum. Note that string lengths are always given in code units. Only in the 5828-bit library is such a length the same as the number of bytes in the string. 583<a name="newlines"></a></P> 584<br><a name="SEC16" href="#TOC1">NEWLINES</a><br> 585<P> 586PCRE2 supports five different conventions for indicating line breaks in 587strings: a single CR (carriage return) character, a single LF (linefeed) 588character, the two-character sequence CRLF, any of the three preceding, or any 589Unicode newline sequence. The Unicode newline sequences are the three just 590mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, 591U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS 592(paragraph separator, U+2029). 593</P> 594<P> 595Each of the first three conventions is used by at least one operating system as 596its standard newline sequence. When PCRE2 is built, a default can be specified. 597If it is not, the default is set to LF, which is the Unix standard. However, 598the newline convention can be changed by an application when calling 599<b>pcre2_compile()</b>, or it can be specified by special text at the start of 600the pattern itself; this overrides any other settings. See the 601<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 602page for details of the special character sequences. 603</P> 604<P> 605In the PCRE2 documentation the word "newline" is used to mean "the character or 606pair of characters that indicate a line break". The choice of newline 607convention affects the handling of the dot, circumflex, and dollar 608metacharacters, the handling of #-comments in /x mode, and, when CRLF is a 609recognized line ending sequence, the match position advancement for a 610non-anchored pattern. There is more detail about this in the 611<a href="#matchoptions">section on <b>pcre2_match()</b> options</a> 612below. 613</P> 614<P> 615The choice of newline convention does not affect the interpretation of 616the \n or \r escape sequences, nor does it affect what \R matches; this has 617its own separate convention. 618</P> 619<br><a name="SEC17" href="#TOC1">MULTITHREADING</a><br> 620<P> 621In a multithreaded application it is important to keep thread-specific data 622separate from data that can be shared between threads. The PCRE2 library code 623itself is thread-safe: it contains no static or global variables. The API is 624designed to be fairly simple for non-threaded applications while at the same 625time ensuring that multithreaded applications can use it. 626</P> 627<P> 628There are several different blocks of data that are used to pass information 629between the application and the PCRE2 libraries. 630</P> 631<br><b> 632The compiled pattern 633</b><br> 634<P> 635A pointer to the compiled form of a pattern is returned to the user when 636<b>pcre2_compile()</b> is successful. The data in the compiled pattern is fixed, 637and does not change when the pattern is matched. Therefore, it is thread-safe, 638that is, the same compiled pattern can be used by more than one thread 639simultaneously. For example, an application can compile all its patterns at the 640start, before forking off multiple threads that use them. However, if the 641just-in-time (JIT) optimization feature is being used, it needs separate memory 642stack areas for each thread. See the 643<a href="pcre2jit.html"><b>pcre2jit</b></a> 644documentation for more details. 645</P> 646<P> 647In a more complicated situation, where patterns are compiled only when they are 648first needed, but are still shared between threads, pointers to compiled 649patterns must be protected from simultaneous writing by multiple threads. This 650is somewhat tricky to do correctly. If you know that writing to a pointer is 651atomic in your environment, you can use logic like this: 652<pre> 653 Get a read-only (shared) lock (mutex) for pointer 654 if (pointer == NULL) 655 { 656 Get a write (unique) lock for pointer 657 if (pointer == NULL) pointer = pcre2_compile(... 658 } 659 Release the lock 660 Use pointer in pcre2_match() 661</pre> 662Of course, testing for compilation errors should also be included in the code. 663</P> 664<P> 665The reason for checking the pointer a second time is as follows: Several 666threads may have acquired the shared lock and tested the pointer for being 667NULL, but only one of them will be given the write lock, with the rest kept 668waiting. The winning thread will compile the pattern and store the result. 669After this thread releases the write lock, another thread will get it, and if 670it does not retest pointer for being NULL, will recompile the pattern and 671overwrite the pointer, creating a memory leak and possibly causing other 672issues. 673</P> 674<P> 675In an environment where writing to a pointer may not be atomic, the above logic 676is not sufficient. The thread that is doing the compiling may be descheduled 677after writing only part of the pointer, which could cause other threads to use 678an invalid value. Instead of checking the pointer itself, a separate "pointer 679is valid" flag (that can be updated atomically) must be used: 680<pre> 681 Get a read-only (shared) lock (mutex) for pointer 682 if (!pointer_is_valid) 683 { 684 Get a write (unique) lock for pointer 685 if (!pointer_is_valid) 686 { 687 pointer = pcre2_compile(... 688 pointer_is_valid = TRUE 689 } 690 } 691 Release the lock 692 Use pointer in pcre2_match() 693</pre> 694If JIT is being used, but the JIT compilation is not being done immediately 695(perhaps waiting to see if the pattern is used often enough), similar logic is 696required. JIT compilation updates a value within the compiled code block, so a 697thread must gain unique write access to the pointer before calling 698<b>pcre2_jit_compile()</b>. Alternatively, <b>pcre2_code_copy()</b> or 699<b>pcre2_code_copy_with_tables()</b> can be used to obtain a private copy of the 700compiled code before calling the JIT compiler. 701</P> 702<br><b> 703Context blocks 704</b><br> 705<P> 706The next main section below introduces the idea of "contexts" in which PCRE2 707functions are called. A context is nothing more than a collection of parameters 708that control the way PCRE2 operates. Grouping a number of parameters together 709in a context is a convenient way of passing them to a PCRE2 function without 710using lots of arguments. The parameters that are stored in contexts are in some 711sense "advanced features" of the API. Many straightforward applications will 712not need to use contexts. 713</P> 714<P> 715In a multithreaded application, if the parameters in a context are values that 716are never changed, the same context can be used by all the threads. However, if 717any thread needs to change any value in a context, it must make its own 718thread-specific copy. 719</P> 720<br><b> 721Match blocks 722</b><br> 723<P> 724The matching functions need a block of memory for storing the results of a 725match. This includes details of what was matched, as well as additional 726information such as the name of a (*MARK) setting. Each thread must provide its 727own copy of this memory. 728</P> 729<br><a name="SEC18" href="#TOC1">PCRE2 CONTEXTS</a><br> 730<P> 731Some PCRE2 functions have a lot of parameters, many of which are used only by 732specialist applications, for example, those that use custom memory management 733or non-standard character tables. To keep function argument lists at a 734reasonable size, and at the same time to keep the API extensible, "uncommon" 735parameters are passed to certain functions in a <b>context</b> instead of 736directly. A context is just a block of memory that holds the parameter values. 737Applications that do not need to adjust any of the context parameters can pass 738NULL when a context pointer is required. 739</P> 740<P> 741There are three different types of context: a general context that is relevant 742for several PCRE2 operations, a compile-time context, and a match-time context. 743</P> 744<br><b> 745The general context 746</b><br> 747<P> 748At present, this context just contains pointers to (and data for) external 749memory management functions that are called from several places in the PCRE2 750library. The context is named `general' rather than specifically `memory' 751because in future other fields may be added. If you do not want to supply your 752own custom memory management functions, you do not need to bother with a 753general context. A general context is created by: 754<br> 755<br> 756<b>pcre2_general_context *pcre2_general_context_create(</b> 757<b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 758<b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 759<br> 760<br> 761The two function pointers specify custom memory management functions, whose 762prototypes are: 763<pre> 764 <b>void *private_malloc(PCRE2_SIZE, void *);</b> 765 <b>void private_free(void *, void *);</b> 766</pre> 767Whenever code in PCRE2 calls these functions, the final argument is the value 768of <i>memory_data</i>. Either of the first two arguments of the creation 769function may be NULL, in which case the system memory management functions 770<i>malloc()</i> and <i>free()</i> are used. (This is not currently useful, as 771there are no other fields in a general context, but in future there might be.) 772The <i>private_malloc()</i> function is used (if supplied) to obtain memory for 773storing the context, and all three values are saved as part of the context. 774</P> 775<P> 776Whenever PCRE2 creates a data block of any kind, the block contains a pointer 777to the <i>free()</i> function that matches the <i>malloc()</i> function that was 778used. When the time comes to free the block, this function is called. 779</P> 780<P> 781A general context can be copied by calling: 782<br> 783<br> 784<b>pcre2_general_context *pcre2_general_context_copy(</b> 785<b> pcre2_general_context *<i>gcontext</i>);</b> 786<br> 787<br> 788The memory used for a general context should be freed by calling: 789<br> 790<br> 791<b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 792<br> 793<br> 794If this function is passed a NULL argument, it returns immediately without 795doing anything. 796<a name="compilecontext"></a></P> 797<br><b> 798The compile context 799</b><br> 800<P> 801A compile context is required if you want to provide an external function for 802stack checking during compilation or to change the default values of any of the 803following compile-time parameters: 804<pre> 805 What \R matches (Unicode newlines or CR, LF, CRLF only) 806 PCRE2's character tables 807 The newline character sequence 808 The compile time nested parentheses limit 809 The maximum length of the pattern string 810 The extra options bits (none set by default) 811</pre> 812A compile context is also required if you are using custom memory management. 813If none of these apply, just pass NULL as the context argument of 814<i>pcre2_compile()</i>. 815</P> 816<P> 817A compile context is created, copied, and freed by the following functions: 818<br> 819<br> 820<b>pcre2_compile_context *pcre2_compile_context_create(</b> 821<b> pcre2_general_context *<i>gcontext</i>);</b> 822<br> 823<br> 824<b>pcre2_compile_context *pcre2_compile_context_copy(</b> 825<b> pcre2_compile_context *<i>ccontext</i>);</b> 826<br> 827<br> 828<b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 829<br> 830<br> 831A compile context is created with default values for its parameters. These can 832be changed by calling the following functions, which return 0 on success, or 833PCRE2_ERROR_BADDATA if invalid data is detected. 834<br> 835<br> 836<b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 837<b> uint32_t <i>value</i>);</b> 838<br> 839<br> 840The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF, 841or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line 842ending sequence. The value is used by the JIT compiler and by the two 843interpreted matching functions, <i>pcre2_match()</i> and 844<i>pcre2_dfa_match()</i>. 845<br> 846<br> 847<b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 848<b> const uint8_t *<i>tables</i>);</b> 849<br> 850<br> 851The value must be the result of a call to <b>pcre2_maketables()</b>, whose only 852argument is a general context. This function builds a set of character tables 853in the current locale. 854<br> 855<br> 856<b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 857<b> uint32_t <i>extra_options</i>);</b> 858<br> 859<br> 860As PCRE2 has developed, almost all the 32 option bits that are available in 861the <i>options</i> argument of <b>pcre2_compile()</b> have been used up. To avoid 862running out, the compile context contains a set of extra option bits which are 863used for some newer, assumed rarer, options. This function sets those bits. It 864always sets all the bits (either on or off). It does not modify any existing 865setting. The available options are defined in the section entitled "Extra 866compile options" 867<a href="#extracompileoptions">below.</a> 868<br> 869<br> 870<b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 871<b> PCRE2_SIZE <i>value</i>);</b> 872<br> 873<br> 874This sets a maximum length, in code units, for any pattern string that is 875compiled with this context. If the pattern is longer, an error is generated. 876This facility is provided so that applications that accept patterns from 877external sources can limit their size. The default is the largest number that a 878PCRE2_SIZE variable can hold, which is effectively unlimited. 879<br> 880<br> 881<b>int pcre2_set_max_pattern_compiled_length(</b> 882<b> pcre2_compile_context *<i>ccontext</i>, PCRE2_SIZE <i>value</i>);</b> 883<br> 884<br> 885This sets a maximum size, in bytes, for the memory needed to hold the compiled 886version of a pattern that is compiled with this context. If the pattern needs 887more memory, an error is generated. This facility is provided so that 888applications that accept patterns from external sources can limit the amount of 889memory they use. The default is the largest number that a PCRE2_SIZE variable 890can hold, which is effectively unlimited. 891<br> 892<br> 893<b>int pcre2_set_max_varlookbehind(pcre2_compile_contest *<i>ccontext</i>,</b> 894<b>" uint32_t <i>value</i>);</b> 895<br> 896<br> 897This sets a maximum length for the number of characters matched by a 898variable-length lookbehind assertion. The default is set when PCRE2 is built, 899with the ultimate default being 255, the same as Perl. Lookbehind assertions 900without a bounding length are not supported. 901<br> 902<br> 903<b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 904<b> uint32_t <i>value</i>);</b> 905<br> 906<br> 907This specifies which characters or character sequences are to be recognized as 908newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only), 909PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character 910sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), 911PCRE2_NEWLINE_ANY (any Unicode newline sequence), or PCRE2_NEWLINE_NUL (the 912NUL character, that is a binary zero). 913</P> 914<P> 915A pattern can override the value set in the compile context by starting with a 916sequence such as (*CRLF). See the 917<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 918page for details. 919</P> 920<P> 921When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE 922option, the newline convention affects the recognition of the end of internal 923comments starting with #. The value is saved with the compiled pattern for 924subsequent use by the JIT compiler and by the two interpreted matching 925functions, <i>pcre2_match()</i> and <i>pcre2_dfa_match()</i>. 926<br> 927<br> 928<b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 929<b> uint32_t <i>value</i>);</b> 930<br> 931<br> 932This parameter adjusts the limit, set when PCRE2 is built (default 250), on the 933depth of parenthesis nesting in a pattern. This limit stops rogue patterns 934using up too much system stack when being compiled. The limit applies to 935parentheses of all kinds, not just capturing parentheses. 936<br> 937<br> 938<b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 939<b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 940<br> 941<br> 942There is at least one application that runs PCRE2 in threads with very limited 943system stack, where running out of stack is to be avoided at all costs. The 944parenthesis limit above cannot take account of how much stack is actually 945available during compilation. For a finer control, you can supply a function 946that is called whenever <b>pcre2_compile()</b> starts to compile a parenthesized 947part of a pattern. This function can check the actual stack size (or anything 948else that it wants to, of course). 949</P> 950<P> 951The first argument to the callout function gives the current depth of 952nesting, and the second is user data that is set up by the last argument of 953<b>pcre2_set_compile_recursion_guard()</b>. The callout function should return 954zero if all is well, or non-zero to force an error. 955<a name="matchcontext"></a></P> 956<br><b> 957The match context 958</b><br> 959<P> 960A match context is required if you want to: 961<pre> 962 Set up a callout function 963 Set an offset limit for matching an unanchored pattern 964 Change the limit on the amount of heap used when matching 965 Change the backtracking match limit 966 Change the backtracking depth limit 967 Set custom memory management specifically for the match 968</pre> 969If none of these apply, just pass NULL as the context argument of 970<b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or <b>pcre2_jit_match()</b>. 971</P> 972<P> 973A match context is created, copied, and freed by the following functions: 974<br> 975<br> 976<b>pcre2_match_context *pcre2_match_context_create(</b> 977<b> pcre2_general_context *<i>gcontext</i>);</b> 978<br> 979<br> 980<b>pcre2_match_context *pcre2_match_context_copy(</b> 981<b> pcre2_match_context *<i>mcontext</i>);</b> 982<br> 983<br> 984<b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 985<br> 986<br> 987A match context is created with default values for its parameters. These can 988be changed by calling the following functions, which return 0 on success, or 989PCRE2_ERROR_BADDATA if invalid data is detected. 990<br> 991<br> 992<b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 993<b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 994<b> void *<i>callout_data</i>);</b> 995<br> 996<br> 997This sets up a callout function for PCRE2 to call at specified points 998during a matching operation. Details are given in the 999<a href="pcre2callout.html"><b>pcre2callout</b></a> 1000documentation. 1001<br> 1002<br> 1003<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 1004<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 1005<b> void *<i>callout_data</i>);</b> 1006<br> 1007<br> 1008This sets up a callout function for PCRE2 to call after each substitution 1009made by <b>pcre2_substitute()</b>. Details are given in the section entitled 1010"Creating a new string with substitutions" 1011<a href="#substitutions">below.</a> 1012<br> 1013<br> 1014<b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 1015<b> PCRE2_SIZE <i>value</i>);</b> 1016<br> 1017<br> 1018The <i>offset_limit</i> parameter limits how far an unanchored search can 1019advance in the subject string. The default value is PCRE2_UNSET. The 1020<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> functions return 1021PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given 1022offset is not found. The <b>pcre2_substitute()</b> function makes no more 1023substitutions. 1024</P> 1025<P> 1026For example, if the pattern /abc/ is matched against "123abc" with an offset 1027limit less than 3, the result is PCRE2_ERROR_NOMATCH. A match can never be 1028found if the <i>startoffset</i> argument of <b>pcre2_match()</b>, 1029<b>pcre2_dfa_match()</b>, or <b>pcre2_substitute()</b> is greater than the offset 1030limit set in the match context. 1031</P> 1032<P> 1033When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT option when 1034calling <b>pcre2_compile()</b> so that when JIT is in use, different code can be 1035compiled. If a match is started with a non-default match limit when 1036PCRE2_USE_OFFSET_LIMIT is not set, an error is generated. 1037</P> 1038<P> 1039The offset limit facility can be used to track progress when searching large 1040subject strings or to limit the extent of global substitutions. See also the 1041PCRE2_FIRSTLINE option, which requires a match to start before or at the first 1042newline that follows the start of matching in the subject. If this is set with 1043an offset limit, a match must occur in the first line and also within the 1044offset limit. In other words, whichever limit comes first is used. 1045<br> 1046<br> 1047<b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 1048<b> uint32_t <i>value</i>);</b> 1049<br> 1050<br> 1051The <i>heap_limit</i> parameter specifies, in units of kibibytes (1024 bytes), 1052the maximum amount of heap memory that <b>pcre2_match()</b> may use to hold 1053backtracking information when running an interpretive match. This limit also 1054applies to <b>pcre2_dfa_match()</b>, which may use the heap when processing 1055patterns with a lot of nested pattern recursion or lookarounds or atomic 1056groups. This limit does not apply to matching with the JIT optimization, which 1057has its own memory control arrangements (see the 1058<a href="pcre2jit.html"><b>pcre2jit</b></a> 1059documentation for more details). If the limit is reached, the negative error 1060code PCRE2_ERROR_HEAPLIMIT is returned. The default limit can be set when PCRE2 1061is built; if it is not, the default is set very large and is essentially 1062unlimited. 1063</P> 1064<P> 1065A value for the heap limit may also be supplied by an item at the start of a 1066pattern of the form 1067<pre> 1068 (*LIMIT_HEAP=ddd) 1069</pre> 1070where ddd is a decimal number. However, such a setting is ignored unless ddd is 1071less than the limit set by the caller of <b>pcre2_match()</b> or, if no such 1072limit is set, less than the default. 1073</P> 1074<P> 1075The <b>pcre2_match()</b> function always needs some heap memory, so setting a 1076value of zero guarantees a "heap limit exceeded" error. Details of how 1077<b>pcre2_match()</b> uses the heap are given in the 1078<a href="pcre2perform.html"><b>pcre2perform</b></a> 1079documentation. 1080</P> 1081<P> 1082For <b>pcre2_dfa_match()</b>, a vector on the system stack is used when 1083processing pattern recursions, lookarounds, or atomic groups, and only if this 1084is not big enough is heap memory used. In this case, setting a value of zero 1085disables the use of the heap. 1086<br> 1087<br> 1088<b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 1089<b> uint32_t <i>value</i>);</b> 1090<br> 1091<br> 1092The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using 1093up too many computing resources when processing patterns that are not going to 1094match, but which have a very large number of possibilities in their search 1095trees. The classic example is a pattern that uses nested unlimited repeats. 1096</P> 1097<P> 1098There is an internal counter in <b>pcre2_match()</b> that is incremented each 1099time round its main matching loop. If this value reaches the match limit, 1100<b>pcre2_match()</b> returns the negative value PCRE2_ERROR_MATCHLIMIT. This has 1101the effect of limiting the amount of backtracking that can take place. For 1102patterns that are not anchored, the count restarts from zero for each position 1103in the subject string. This limit also applies to <b>pcre2_dfa_match()</b>, 1104though the counting is done in a different way. 1105</P> 1106<P> 1107When <b>pcre2_match()</b> is called with a pattern that was successfully 1108processed by <b>pcre2_jit_compile()</b>, the way in which matching is executed 1109is entirely different. However, there is still the possibility of runaway 1110matching that goes on for a very long time, and so the <i>match_limit</i> value 1111is also used in this case (but in a different way) to limit how long the 1112matching can continue. 1113</P> 1114<P> 1115The default value for the limit can be set when PCRE2 is built; the default is 111610 million, which handles all but the most extreme cases. A value for the match 1117limit may also be supplied by an item at the start of a pattern of the form 1118<pre> 1119 (*LIMIT_MATCH=ddd) 1120</pre> 1121where ddd is a decimal number. However, such a setting is ignored unless ddd is 1122less than the limit set by the caller of <b>pcre2_match()</b> or 1123<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1124<br> 1125<br> 1126<b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 1127<b> uint32_t <i>value</i>);</b> 1128<br> 1129<br> 1130This parameter limits the depth of nested backtracking in <b>pcre2_match()</b>. 1131Each time a nested backtracking point is passed, a new memory frame is used 1132to remember the state of matching at that point. Thus, this parameter 1133indirectly limits the amount of memory that is used in a match. However, 1134because the size of each memory frame depends on the number of capturing 1135parentheses, the actual memory limit varies from pattern to pattern. This limit 1136was more useful in versions before 10.30, where function recursion was used for 1137backtracking. 1138</P> 1139<P> 1140The depth limit is not relevant, and is ignored, when matching is done using 1141JIT compiled code. However, it is supported by <b>pcre2_dfa_match()</b>, which 1142uses it to limit the depth of nested internal recursive function calls that 1143implement atomic groups, lookaround assertions, and pattern recursions. This 1144limits, indirectly, the amount of system stack that is used. It was more useful 1145in versions before 10.32, when stack memory was used for local workspace 1146vectors for recursive function calls. From version 10.32, only local variables 1147are allocated on the stack and as each call uses only a few hundred bytes, even 1148a small stack can support quite a lot of recursion. 1149</P> 1150<P> 1151If the depth of internal recursive function calls is great enough, local 1152workspace vectors are allocated on the heap from version 10.32 onwards, so the 1153depth limit also indirectly limits the amount of heap memory that is used. A 1154recursive pattern such as /(.(?2))((?1)|)/, when matched to a very long string 1155using <b>pcre2_dfa_match()</b>, can use a great deal of memory. However, it is 1156probably better to limit heap usage directly by calling 1157<b>pcre2_set_heap_limit()</b>. 1158</P> 1159<P> 1160The default value for the depth limit can be set when PCRE2 is built; if it is 1161not, the default is set to the same value as the default for the match limit. 1162If the limit is exceeded, <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> 1163returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be 1164supplied by an item at the start of a pattern of the form 1165<pre> 1166 (*LIMIT_DEPTH=ddd) 1167</pre> 1168where ddd is a decimal number. However, such a setting is ignored unless ddd is 1169less than the limit set by the caller of <b>pcre2_match()</b> or 1170<b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1171</P> 1172<br><a name="SEC19" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> 1173<P> 1174<b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 1175</P> 1176<P> 1177The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to find 1178the value of certain configuration parameters and to discover which optional 1179features have been compiled into the PCRE2 library. The 1180<a href="pcre2build.html"><b>pcre2build</b></a> 1181documentation has more details about these features. 1182</P> 1183<P> 1184The first argument for <b>pcre2_config()</b> specifies which information is 1185required. The second argument is a pointer to memory into which the information 1186is placed. If NULL is passed, the function returns the amount of memory that is 1187needed for the requested information. For calls that return numerical values, 1188the value is in bytes; when requesting these values, <i>where</i> should point 1189to appropriately aligned memory. For calls that return strings, the required 1190length is given in code units, not counting the terminating zero. 1191</P> 1192<P> 1193When requesting information, the returned value from <b>pcre2_config()</b> is 1194non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if 1195the value in the first argument is not recognized. The following information is 1196available: 1197<pre> 1198 PCRE2_CONFIG_BSR 1199</pre> 1200The output is a uint32_t integer whose value indicates what character 1201sequences the \R escape sequence matches by default. A value of 1202PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a 1203value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The 1204default can be overridden when a pattern is compiled. 1205<pre> 1206 PCRE2_CONFIG_COMPILED_WIDTHS 1207</pre> 1208The output is a uint32_t integer whose lower bits indicate which code unit 1209widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, 1210and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively. 1211<pre> 1212 PCRE2_CONFIG_DEPTHLIMIT 1213</pre> 1214The output is a uint32_t integer that gives the default limit for the depth of 1215nested backtracking in <b>pcre2_match()</b> or the depth of nested recursions, 1216lookarounds, and atomic groups in <b>pcre2_dfa_match()</b>. Further details are 1217given with <b>pcre2_set_depth_limit()</b> above. 1218<pre> 1219 PCRE2_CONFIG_HEAPLIMIT 1220</pre> 1221The output is a uint32_t integer that gives, in kibibytes, the default limit 1222for the amount of heap memory used by <b>pcre2_match()</b> or 1223<b>pcre2_dfa_match()</b>. Further details are given with 1224<b>pcre2_set_heap_limit()</b> above. 1225<pre> 1226 PCRE2_CONFIG_JIT 1227</pre> 1228The output is a uint32_t integer that is set to one if support for just-in-time 1229compiling is included in the library; otherwise it is set to zero. Note that 1230having the support in the library does not guarantee that JIT will be used for 1231any given match. See the 1232<a href="pcre2jit.html"><b>pcre2jit</b></a> 1233documentation for more details. 1234<pre> 1235 PCRE2_CONFIG_JITTARGET 1236</pre> 1237The <i>where</i> argument should point to a buffer that is at least 48 code 1238units long. (The exact length required can be found by calling 1239<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a 1240string that contains the name of the architecture for which the JIT compiler is 1241configured, for example "x86 32bit (little endian + unaligned)". If JIT support 1242is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of 1243code units used is returned. This is the length of the string, plus one unit 1244for the terminating zero. 1245<pre> 1246 PCRE2_CONFIG_LINKSIZE 1247</pre> 1248The output is a uint32_t integer that contains the number of bytes used for 1249internal linkage in compiled regular expressions. When PCRE2 is configured, the 1250value can be set to 2, 3, or 4, with the default being 2. This is the value 1251that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is 1252compiled, a value of 3 is rounded up to 4, and when the 32-bit library is 1253compiled, internal linkages always use 4 bytes, so the configured value is not 1254relevant. 1255</P> 1256<P> 1257The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all 1258but the most massive patterns, since it allows the size of the compiled pattern 1259to be up to 65535 code units. Larger values allow larger regular expressions to 1260be compiled by those two libraries, but at the expense of slower matching. 1261<pre> 1262 PCRE2_CONFIG_MATCHLIMIT 1263</pre> 1264The output is a uint32_t integer that gives the default match limit for 1265<b>pcre2_match()</b>. Further details are given with 1266<b>pcre2_set_match_limit()</b> above. 1267<pre> 1268 PCRE2_CONFIG_NEWLINE 1269</pre> 1270The output is a uint32_t integer whose value specifies the default character 1271sequence that is recognized as meaning "newline". The values are: 1272<pre> 1273 PCRE2_NEWLINE_CR Carriage return (CR) 1274 PCRE2_NEWLINE_LF Linefeed (LF) 1275 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 1276 PCRE2_NEWLINE_ANY Any Unicode line ending 1277 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 1278 PCRE2_NEWLINE_NUL The NUL character (binary zero) 1279</pre> 1280The default should normally correspond to the standard sequence for your 1281operating system. 1282<pre> 1283 PCRE2_CONFIG_NEVER_BACKSLASH_C 1284</pre> 1285The output is a uint32_t integer that is set to one if the use of \C was 1286permanently disabled when PCRE2 was built; otherwise it is set to zero. 1287<pre> 1288 PCRE2_CONFIG_PARENSLIMIT 1289</pre> 1290The output is a uint32_t integer that gives the maximum depth of nesting 1291of parentheses (of any kind) in a pattern. This limit is imposed to cap the 1292amount of system stack used when a pattern is compiled. It is specified when 1293PCRE2 is built; the default is 250. This limit does not take into account the 1294stack that may already be used by the calling application. For finer control 1295over compilation stack usage, see <b>pcre2_set_compile_recursion_guard()</b>. 1296<pre> 1297 PCRE2_CONFIG_STACKRECURSE 1298</pre> 1299This parameter is obsolete and should not be used in new code. The output is a 1300uint32_t integer that is always set to zero. 1301<pre> 1302 PCRE2_CONFIG_TABLES_LENGTH 1303</pre> 1304The output is a uint32_t integer that gives the length of PCRE2's character 1305processing tables in bytes. For details of these tables see the 1306<a href="#localesupport">section on locale support</a> 1307below. 1308<pre> 1309 PCRE2_CONFIG_UNICODE_VERSION 1310</pre> 1311The <i>where</i> argument should point to a buffer that is at least 24 code 1312units long. (The exact length required can be found by calling 1313<b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled 1314without Unicode support, the buffer is filled with the text "Unicode not 1315supported". Otherwise, the Unicode version string (for example, "8.0.0") is 1316inserted. The number of code units used is returned. This is the length of the 1317string plus one unit for the terminating zero. 1318<pre> 1319 PCRE2_CONFIG_UNICODE 1320</pre> 1321The output is a uint32_t integer that is set to one if Unicode support is 1322available; otherwise it is set to zero. Unicode support implies UTF support. 1323<pre> 1324 PCRE2_CONFIG_VERSION 1325</pre> 1326The <i>where</i> argument should point to a buffer that is at least 24 code 1327units long. (The exact length required can be found by calling 1328<b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with 1329the PCRE2 version string, zero-terminated. The number of code units used is 1330returned. This is the length of the string plus one unit for the terminating 1331zero. 1332<a name="compiling"></a></P> 1333<br><a name="SEC20" href="#TOC1">COMPILING A PATTERN</a><br> 1334<P> 1335<b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 1336<b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 1337<b> pcre2_compile_context *<i>ccontext</i>);</b> 1338<br> 1339<br> 1340<b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 1341<br> 1342<br> 1343<b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 1344<br> 1345<br> 1346<b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 1347</P> 1348<P> 1349The <b>pcre2_compile()</b> function compiles a pattern into an internal form. 1350The pattern is defined by a pointer to a string of code units and a length in 1351code units. If the pattern is zero-terminated, the length can be specified as 1352PCRE2_ZERO_TERMINATED. A NULL pattern pointer with a length of zero is treated 1353as an empty string (NULL with a non-zero length causes an error return). The 1354function returns a pointer to a block of memory that contains the compiled 1355pattern and related data, or NULL if an error occurred. 1356</P> 1357<P> 1358If the compile context argument <i>ccontext</i> is NULL, memory for the compiled 1359pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from 1360the same memory function that was used for the compile context. The caller must 1361free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed. 1362If <b>pcre2_code_free()</b> is called with a NULL argument, it returns 1363immediately, without doing anything. 1364</P> 1365<P> 1366The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new 1367memory, using the same memory allocator as was used for the original. However, 1368if the code has been processed by the JIT compiler (see 1369<a href="#jitcompiling">below),</a> 1370the JIT information cannot be copied (because it is position-dependent). 1371The new copy can initially be used only for non-JIT matching, though it can be 1372passed to <b>pcre2_jit_compile()</b> if required. If <b>pcre2_code_copy()</b> is 1373called with a NULL argument, it returns NULL. 1374</P> 1375<P> 1376The <b>pcre2_code_copy()</b> function provides a way for individual threads in a 1377multithreaded application to acquire a private copy of shared compiled code. 1378However, it does not make a copy of the character tables used by the compiled 1379pattern; the new pattern code points to the same tables as the original code. 1380(See 1381<a href="#jitcompiling">"Locale Support"</a> 1382below for details of these character tables.) In many applications the same 1383tables are used throughout, so this behaviour is appropriate. Nevertheless, 1384there are occasions when a copy of a compiled pattern and the relevant tables 1385are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility. 1386Copies of both the code and the tables are made, with the new code pointing to 1387the new tables. The memory for the new tables is automatically freed when 1388<b>pcre2_code_free()</b> is called for the new copy of the compiled code. If 1389<b>pcre2_code_copy_with_tables()</b> is called with a NULL argument, it returns 1390NULL. 1391</P> 1392<P> 1393NOTE: When one of the matching functions is called, pointers to the compiled 1394pattern and the subject string are set in the match data block so that they can 1395be referenced by the substring extraction functions after a successful match. 1396After running a match, you must not free a compiled pattern or a subject string 1397until after all operations on the 1398<a href="#matchdatablock">match data block</a> 1399have taken place, unless, in the case of the subject string, you have used the 1400PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 1401"Option bits for <b>pcre2_match()</b>" 1402<a href="#matchoptions>">below.</a> 1403</P> 1404<P> 1405The <i>options</i> argument for <b>pcre2_compile()</b> contains various bit 1406settings that affect the compilation. It should be zero if none of them are 1407required. The available options are described below. Some of them (in 1408particular, those that are compatible with Perl, but some others as well) can 1409also be set and unset from within the pattern (see the detailed description in 1410the 1411<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1412documentation). 1413</P> 1414<P> 1415For those options that can be different in different parts of the pattern, the 1416contents of the <i>options</i> argument specifies their settings at the start of 1417compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK 1418options can be set at the time of matching as well as at compile time. 1419</P> 1420<P> 1421Some additional options and less frequently required compile-time parameters 1422(for example, the newline setting) can be provided in a compile context (as 1423described 1424<a href="#compilecontext">above).</a> 1425</P> 1426<P> 1427If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns 1428NULL immediately. Otherwise, the variables to which these point are set to an 1429error code and an offset (number of code units) within the pattern, 1430respectively, when <b>pcre2_compile()</b> returns NULL because a compilation 1431error has occurred. 1432</P> 1433<P> 1434There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return 1435if it finds an error in the pattern. There are also some negative error codes 1436that are used for invalid UTF strings when validity checking is in force. These 1437are the same as given by <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and 1438are described in the 1439<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1440documentation. There is no separate documentation for the positive error codes, 1441because the textual error messages that are obtained by calling the 1442<b>pcre2_get_error_message()</b> function (see "Obtaining a textual error 1443message" 1444<a href="#geterrormessage">below)</a> 1445should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined 1446for both positive and negative error codes in <b>pcre2.h</b>. When compilation 1447is successful <i>errorcode</i> is set to a value that returns the message "no 1448error" if passed to <b>pcre2_get_error_message()</b>. 1449</P> 1450<P> 1451The value returned in <i>erroroffset</i> is an indication of where in the 1452pattern an error occurred. When there is no error, zero is returned. A non-zero 1453value is not necessarily the furthest point in the pattern that was read. For 1454example, after the error "lookbehind assertion is not fixed length", the error 1455offset points to the start of the failing assertion. For an invalid UTF-8 or 1456UTF-16 string, the offset is that of the first code unit of the failing 1457character. 1458</P> 1459<P> 1460Some errors are not detected until the whole pattern has been scanned; in these 1461cases, the offset passed back is the length of the pattern. Note that the 1462offset is in code units, not characters, even in a UTF mode. It may sometimes 1463point into the middle of a UTF-8 or UTF-16 character. 1464</P> 1465<P> 1466This code fragment shows a typical straightforward call to 1467<b>pcre2_compile()</b>: 1468<pre> 1469 pcre2_code *re; 1470 PCRE2_SIZE erroffset; 1471 int errorcode; 1472 re = pcre2_compile( 1473 "^A.*Z", /* the pattern */ 1474 PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */ 1475 0, /* default options */ 1476 &errorcode, /* for error code */ 1477 &erroffset, /* for error offset */ 1478 NULL); /* no compile context */ 1479 1480</PRE> 1481</P> 1482<br><b> 1483Main compile options 1484</b><br> 1485<P> 1486The following names for option bits are defined in the <b>pcre2.h</b> header 1487file: 1488<pre> 1489 PCRE2_ANCHORED 1490</pre> 1491If this bit is set, the pattern is forced to be "anchored", that is, it is 1492constrained to match only at the first matching point in the string that is 1493being searched (the "subject string"). This effect can also be achieved by 1494appropriate constructs in the pattern itself, which is the only way to do it in 1495Perl. 1496<pre> 1497 PCRE2_ALLOW_EMPTY_CLASS 1498</pre> 1499By default, for compatibility with Perl, a closing square bracket that 1500immediately follows an opening one is treated as a data character for the 1501class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which 1502therefore contains no characters and so can never match. 1503<pre> 1504 PCRE2_ALT_BSUX 1505</pre> 1506This option request alternative handling of three escape sequences, which 1507makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: 1508</P> 1509<P> 1510(1) \U matches an upper case "U" character; by default \U causes a compile 1511time error (Perl uses \U to upper case subsequent characters). 1512</P> 1513<P> 1514(2) \u matches a lower case "u" character unless it is followed by four 1515hexadecimal digits, in which case the hexadecimal number defines the code point 1516to match. By default, \u causes a compile time error (Perl uses it to upper 1517case the following character). 1518</P> 1519<P> 1520(3) \x matches a lower case "x" character unless it is followed by two 1521hexadecimal digits, in which case the hexadecimal number defines the code point 1522to match. By default, as in Perl, a hexadecimal number is always expected after 1523\x, but it may have zero, one, or two digits (so, for example, \xz matches a 1524binary zero character followed by z). 1525</P> 1526<P> 1527ECMAscript 6 added additional functionality to \u. This can be accessed using 1528the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile options" 1529<a href="#extracompileoptions">below).</a> 1530Note that this alternative escape handling applies only to patterns. Neither of 1531these options affects the processing of replacement strings passed to 1532<b>pcre2_substitute()</b>. 1533<pre> 1534 PCRE2_ALT_CIRCUMFLEX 1535</pre> 1536In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter 1537matches at the start of the subject (unless PCRE2_NOTBOL is set), and also 1538after any internal newline. However, it does not match after a newline at the 1539end of the subject, for compatibility with Perl. If you want a multiline 1540circumflex also to match after a terminating newline, you must set 1541PCRE2_ALT_CIRCUMFLEX. 1542<pre> 1543 PCRE2_ALT_VERBNAMES 1544</pre> 1545By default, for compatibility with Perl, the name in any verb sequence such as 1546(*MARK:NAME) is any sequence of characters that does not include a closing 1547parenthesis. The name is not processed in any way, and it is not possible to 1548include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES 1549option is set, normal backslash processing is applied to verb names and only an 1550unescaped closing parenthesis terminates the name. A closing parenthesis can be 1551included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED 1552or PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped 1553whitespace in verb names is skipped and #-comments are recognized, exactly as 1554in the rest of the pattern. 1555<pre> 1556 PCRE2_AUTO_CALLOUT 1557</pre> 1558If this bit is set, <b>pcre2_compile()</b> automatically inserts callout items, 1559all with number 255, before each pattern item, except immediately before or 1560after an explicit callout in the pattern. For discussion of the callout 1561facility, see the 1562<a href="pcre2callout.html"><b>pcre2callout</b></a> 1563documentation. 1564<pre> 1565 PCRE2_CASELESS 1566</pre> 1567If this bit is set, letters in the pattern match both upper and lower case 1568letters in the subject. It is equivalent to Perl's /i option, and it can be 1569changed within a pattern by a (?i) option setting. If either PCRE2_UTF or 1570PCRE2_UCP is set, Unicode properties are used for all characters with more than 1571one other case, and for all characters whose code points are greater than 1572U+007F. Note that there are two ASCII characters, K and S, that, in addition to 1573their lower case ASCII equivalents, are case-equivalent with U+212A (Kelvin 1574sign) and U+017F (long S) respectively. If you do not want this case 1575equivalence, you can suppress it by setting PCRE2_EXTRA_CASELESS_RESTRICT. 1576</P> 1577<P> 1578For lower valued characters with only one other case, a lookup table is used 1579for speed. When neither PCRE2_UTF nor PCRE2_UCP is set, a lookup table is used 1580for all code points less than 256, and higher code points (available only in 158116-bit or 32-bit mode) are treated as not having another case. 1582<pre> 1583 PCRE2_DOLLAR_ENDONLY 1584</pre> 1585If this bit is set, a dollar metacharacter in the pattern matches only at the 1586end of the subject string. Without this option, a dollar also matches 1587immediately before a newline at the end of the string (but not before any other 1588newlines). The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is 1589set. There is no equivalent to this option in Perl, and no way to set it within 1590a pattern. 1591<pre> 1592 PCRE2_DOTALL 1593</pre> 1594If this bit is set, a dot metacharacter in the pattern matches any character, 1595including one that indicates a newline. However, it only ever matches one 1596character, even if newlines are coded as CRLF. Without this option, a dot does 1597not match when the current position in the subject is at a newline. This option 1598is equivalent to Perl's /s option, and it can be changed within a pattern by a 1599(?s) option setting. A negative class such as [^a] always matches newline 1600characters, and the \N escape sequence always matches a non-newline character, 1601independent of the setting of PCRE2_DOTALL. 1602<pre> 1603 PCRE2_DUPNAMES 1604</pre> 1605If this bit is set, names used to identify capture groups need not be unique. 1606This can be helpful for certain types of pattern when it is known that only one 1607instance of the named group can ever be matched. There are more details of 1608named capture groups below; see also the 1609<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1610documentation. 1611<pre> 1612 PCRE2_ENDANCHORED 1613</pre> 1614If this bit is set, the end of any pattern match must be right at the end of 1615the string being searched (the "subject string"). If the pattern match 1616succeeds by reaching (*ACCEPT), but does not reach the end of the subject, the 1617match fails at the current starting point. For unanchored patterns, a new match 1618is then tried at the next starting point. However, if the match succeeds by 1619reaching the end of the pattern, but not the end of the subject, backtracking 1620occurs and an alternative match may be found. Consider these two patterns: 1621<pre> 1622 .(*ACCEPT)|.. 1623 .|.. 1624</pre> 1625If matched against "abc" with PCRE2_ENDANCHORED set, the first matches "c" 1626whereas the second matches "bc". The effect of PCRE2_ENDANCHORED can also be 1627achieved by appropriate constructs in the pattern itself, which is the only way 1628to do it in Perl. 1629</P> 1630<P> 1631For DFA matching with <b>pcre2_dfa_match()</b>, PCRE2_ENDANCHORED applies only 1632to the first (that is, the longest) matched string. Other parallel matches, 1633which are necessarily substrings of the first one, must obviously end before 1634the end of the subject. 1635<pre> 1636 PCRE2_EXTENDED 1637</pre> 1638If this bit is set, most white space characters in the pattern are totally 1639ignored except when escaped, inside a character class, or inside a \Q...\E 1640sequence. However, white space is not allowed within sequences such as (?> that 1641introduce various parenthesized groups, nor within numerical quantifiers such 1642as {1,3}. Ignorable white space is permitted between an item and a following 1643quantifier and between a quantifier and a following + that indicates 1644possessiveness. PCRE2_EXTENDED is equivalent to Perl's /x option, and it can be 1645changed within a pattern by a (?x) option setting. 1646</P> 1647<P> 1648When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recognizes as 1649white space only those characters with code points less than 256 that are 1650flagged as white space in its low-character table. The table is normally 1651created by 1652<a href="pcre2_maketables.html"><b>pcre2_maketables()</b>,</a> 1653which uses the <b>isspace()</b> function to identify space characters. In most 1654ASCII environments, the relevant characters are those with code points 0x0009 1655(tab), 0x000A (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D 1656(carriage return), and 0x0020 (space). 1657</P> 1658<P> 1659When PCRE2 is compiled with Unicode support, in addition to these characters, 1660five more Unicode "Pattern White Space" characters are recognized by 1661PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-right mark), 1662U+200F (right-to-left mark), U+2028 (line separator), and U+2029 (paragraph 1663separator). This set of characters is the same as recognized by Perl's /x 1664option. Note that the horizontal and vertical space characters that are matched 1665by the \h and \v escapes in patterns are a much bigger set. 1666</P> 1667<P> 1668As well as ignoring most white space, PCRE2_EXTENDED also causes characters 1669between an unescaped # outside a character class and the next newline, 1670inclusive, to be ignored, which makes it possible to include comments inside 1671complicated patterns. Note that the end of this type of comment is a literal 1672newline sequence in the pattern; escape sequences that happen to represent a 1673newline do not count. 1674</P> 1675<P> 1676Which characters are interpreted as newlines can be specified by a setting in 1677the compile context that is passed to <b>pcre2_compile()</b> or by a special 1678sequence at the start of the pattern, as described in the section entitled 1679<a href="pcre2pattern.html#newlines">"Newline conventions"</a> 1680in the <b>pcre2pattern</b> documentation. A default is defined when PCRE2 is 1681built. 1682<pre> 1683 PCRE2_EXTENDED_MORE 1684</pre> 1685This option has the effect of PCRE2_EXTENDED, but, in addition, unescaped space 1686and horizontal tab characters are ignored inside a character class. Note: only 1687these two characters are ignored, not the full set of pattern white space 1688characters that are ignored outside a character class. PCRE2_EXTENDED_MORE is 1689equivalent to Perl's /xx option, and it can be changed within a pattern by a 1690(?xx) option setting. 1691<pre> 1692 PCRE2_FIRSTLINE 1693</pre> 1694If this option is set, the start of an unanchored pattern match must be before 1695or at the first newline in the subject string following the start of matching, 1696though the matched text may continue over the newline. If <i>startoffset</i> is 1697non-zero, the limiting newline is not necessarily the first newline in the 1698subject. For example, if the subject string is "abc\nxyz" (where \n 1699represents a single-character newline) a pattern match for "yz" succeeds with 1700PCRE2_FIRSTLINE if <i>startoffset</i> is greater than 3. See also 1701PCRE2_USE_OFFSET_LIMIT, which provides a more general limiting facility. If 1702PCRE2_FIRSTLINE is set with an offset limit, a match must occur in the first 1703line and also within the offset limit. In other words, whichever limit comes 1704first is used. This option has no effect for anchored patterns. 1705<pre> 1706 PCRE2_LITERAL 1707</pre> 1708If this option is set, all meta-characters in the pattern are disabled, and it 1709is treated as a literal string. Matching literal strings with a regular 1710expression engine is not the most efficient way of doing it. If you are doing a 1711lot of literal matching and are worried about efficiency, you should consider 1712using other approaches. The only other main options that are allowed with 1713PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, 1714PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_MATCH_INVALID_UTF, 1715PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and 1716PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and 1717PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an error. 1718<pre> 1719 PCRE2_MATCH_INVALID_UTF 1720</pre> 1721This option forces PCRE2_UTF (see below) and also enables support for matching 1722by <b>pcre2_match()</b> in subject strings that contain invalid UTF sequences. 1723Note, however, that the 16-bit and 32-bit PCRE2 libraries process strings as 1724sequences of uint16_t or uint32_t code points. They cannot find valid UTF 1725sequences within an arbitrary string of bytes unless such sequences are 1726suitably aligned. This facility is not supported for DFA matching. For details, 1727see the 1728<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1729documentation. 1730<pre> 1731 PCRE2_MATCH_UNSET_BACKREF 1732</pre> 1733If this option is set, a backreference to an unset capture group matches an 1734empty string (by default this causes the current matching alternative to fail). 1735A pattern such as (\1)(a) succeeds when this option is set (assuming it can 1736find an "a" in the subject), whereas it fails by default, for Perl 1737compatibility. Setting this option makes PCRE2 behave more like ECMAscript (aka 1738JavaScript). 1739<pre> 1740 PCRE2_MULTILINE 1741</pre> 1742By default, for the purposes of matching "start of line" and "end of line", 1743PCRE2 treats the subject string as consisting of a single line of characters, 1744even if it actually contains newlines. The "start of line" metacharacter (^) 1745matches only at the start of the string, and the "end of line" metacharacter 1746($) matches only at the end of the string, or before a terminating newline 1747(except when PCRE2_DOLLAR_ENDONLY is set). Note, however, that unless 1748PCRE2_DOTALL is set, the "any character" metacharacter (.) does not match at a 1749newline. This behaviour (for ^, $, and dot) is the same as Perl. 1750</P> 1751<P> 1752When PCRE2_MULTILINE it is set, the "start of line" and "end of line" 1753constructs match immediately following or immediately before internal newlines 1754in the subject string, respectively, as well as at the very start and end. This 1755is equivalent to Perl's /m option, and it can be changed within a pattern by a 1756(?m) option setting. Note that the "start of line" metacharacter does not match 1757after a newline at the end of the subject, for compatibility with Perl. 1758However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If 1759there are no newlines in a subject string, or no occurrences of ^ or $ in a 1760pattern, setting PCRE2_MULTILINE has no effect. 1761<pre> 1762 PCRE2_NEVER_BACKSLASH_C 1763</pre> 1764This option locks out the use of \C in the pattern that is being compiled. 1765This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because 1766it may leave the current matching point in the middle of a multi-code-unit 1767character. This option may be useful in applications that process patterns from 1768external sources. Note that there is also a build-time option that permanently 1769locks out the use of \C. 1770<pre> 1771 PCRE2_NEVER_UCP 1772</pre> 1773This option locks out the use of Unicode properties for handling \B, \b, \D, 1774\d, \S, \s, \W, \w, and some of the POSIX character classes, as described 1775for the PCRE2_UCP option below. In particular, it prevents the creator of the 1776pattern from enabling this facility by starting the pattern with (*UCP). This 1777option may be useful in applications that process patterns from external 1778sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error. 1779<pre> 1780 PCRE2_NEVER_UTF 1781</pre> 1782This option locks out interpretation of the pattern as UTF-8, UTF-16, or 1783UTF-32, depending on which library is in use. In particular, it prevents the 1784creator of the pattern from switching to UTF interpretation by starting the 1785pattern with (*UTF). This option may be useful in applications that process 1786patterns from external sources. The combination of PCRE2_UTF and 1787PCRE2_NEVER_UTF causes an error. 1788<pre> 1789 PCRE2_NO_AUTO_CAPTURE 1790</pre> 1791If this option is set, it disables the use of numbered capturing parentheses in 1792the pattern. Any opening parenthesis that is not followed by ? behaves as if it 1793were followed by ?: but named parentheses can still be used for capturing (and 1794they acquire numbers in the usual way). This is the same as Perl's /n option. 1795Note that, when this option is set, references to capture groups 1796(backreferences or recursion/subroutine calls) may only refer to named groups, 1797though the reference can be by name or by number. 1798<pre> 1799 PCRE2_NO_AUTO_POSSESS 1800</pre> 1801If this option is set, it disables "auto-possessification", which is an 1802optimization that, for example, turns a+b into a++b in order to avoid 1803backtracks into a+ that can never be successful. However, if callouts are in 1804use, auto-possessification means that some callouts are never taken. You can 1805set this option if you want the matching functions to do a full unoptimized 1806search and run all the callouts, but it is mainly provided for testing 1807purposes. 1808<pre> 1809 PCRE2_NO_DOTSTAR_ANCHOR 1810</pre> 1811If this option is set, it disables an optimization that is applied when .* is 1812the first significant item in a top-level branch of a pattern, and all the 1813other branches also start with .* or with \A or \G or ^. The optimization is 1814automatically disabled for .* if it is inside an atomic group or a capture 1815group that is the subject of a backreference, or if the pattern contains 1816(*PRUNE) or (*SKIP). When the optimization is not disabled, such a pattern is 1817automatically anchored if PCRE2_DOTALL is set for all the .* items and 1818PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match 1819must start either at the start of the subject or following a newline is 1820remembered. Like other optimizations, this can cause callouts to be skipped. 1821<pre> 1822 PCRE2_NO_START_OPTIMIZE 1823</pre> 1824This is an option whose main effect is at matching time. It does not change 1825what <b>pcre2_compile()</b> generates, but it does affect the output of the JIT 1826compiler. 1827</P> 1828<P> 1829There are a number of optimizations that may occur at the start of a match, in 1830order to speed up the process. For example, if it is known that an unanchored 1831match must start with a specific code unit value, the matching code searches 1832the subject for that value, and fails immediately if it cannot find it, without 1833actually running the main matching function. This means that a special item 1834such as (*COMMIT) at the start of a pattern is not considered until after a 1835suitable starting point for the match has been found. Also, when callouts or 1836(*MARK) items are in use, these "start-up" optimizations can cause them to be 1837skipped if the pattern is never actually used. The start-up optimizations are 1838in effect a pre-scan of the subject that takes place before the pattern is run. 1839</P> 1840<P> 1841The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations, 1842possibly causing performance to suffer, but ensuring that in cases where the 1843result is "no match", the callouts do occur, and that items such as (*COMMIT) 1844and (*MARK) are considered at every possible starting position in the subject 1845string. 1846</P> 1847<P> 1848Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation. 1849Consider the pattern 1850<pre> 1851 (*COMMIT)ABC 1852</pre> 1853When this is compiled, PCRE2 records the fact that a match must start with the 1854character "A". Suppose the subject string is "DEFABC". The start-up 1855optimization scans along the subject, finds "A" and runs the first match 1856attempt from there. The (*COMMIT) item means that the pattern must match the 1857current starting position, which in this case, it does. However, if the same 1858match is run with PCRE2_NO_START_OPTIMIZE set, the initial scan along the 1859subject string does not happen. The first match attempt is run starting from 1860"D" and when this fails, (*COMMIT) prevents any further matches being tried, so 1861the overall result is "no match". 1862</P> 1863<P> 1864As another start-up optimization makes use of a minimum length for a matching 1865subject, which is recorded when possible. Consider the pattern 1866<pre> 1867 (*MARK:1)B(*MARK:2)(X|Y) 1868</pre> 1869The minimum length for a match is two characters. If the subject is "XXBB", the 1870"starting character" optimization skips "XX", then tries to match "BB", which 1871is long enough. In the process, (*MARK:2) is encountered and remembered. When 1872the match attempt fails, the next "B" is found, but there is only one character 1873left, so there are no more attempts, and "no match" is returned with the "last 1874mark seen" set to "2". If NO_START_OPTIMIZE is set, however, matches are tried 1875at every possible starting position, including at the end of the subject, where 1876(*MARK:1) is encountered, but there is no "B", so the "last mark seen" that is 1877returned is "1". In this case, the optimizations do not affect the overall 1878match result, which is still "no match", but they do affect the auxiliary 1879information that is returned. 1880<pre> 1881 PCRE2_NO_UTF_CHECK 1882</pre> 1883When PCRE2_UTF is set, the validity of the pattern as a UTF string is 1884automatically checked. There are discussions about the validity of 1885<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 1886<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 1887and 1888<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 1889in the 1890<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1891document. If an invalid UTF sequence is found, <b>pcre2_compile()</b> returns a 1892negative error code. 1893</P> 1894<P> 1895If you know that your pattern is a valid UTF string, and you want to skip this 1896check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When 1897it is set, the effect of passing an invalid UTF string as a pattern is 1898undefined. It may cause your program to crash or loop. 1899</P> 1900<P> 1901Note that this option can also be passed to <b>pcre2_match()</b> and 1902<b>pcre2_dfa_match()</b>, to suppress UTF validity checking of the subject 1903string. 1904</P> 1905<P> 1906Note also that setting PCRE2_NO_UTF_CHECK at compile time does not disable the 1907error that is given if an escape sequence for an invalid Unicode code point is 1908encountered in the pattern. In particular, the so-called "surrogate" code 1909points (0xd800 to 0xdfff) are invalid. If you want to allow escape sequences 1910such as \x{d800} you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra 1911option, as described in the section entitled "Extra compile options" 1912<a href="#extracompileoptions">below.</a> 1913However, this is possible only in UTF-8 and UTF-32 modes, because these values 1914are not representable in UTF-16. 1915<pre> 1916 PCRE2_UCP 1917</pre> 1918This option has two effects. Firstly, it change the way PCRE2 processes \B, 1919\b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes. By 1920default, only ASCII characters are recognized, but if PCRE2_UCP is set, Unicode 1921properties are used to classify characters. There are some PCRE2_EXTRA 1922options (see below) that add finer control to this behaviour. More details are 1923given in the section on 1924<a href="pcre2pattern.html#genericchartypes">generic character types</a> 1925in the 1926<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1927page. 1928</P> 1929<P> 1930The second effect of PCRE2_UCP is to force the use of Unicode properties for 1931upper/lower casing operations, even when PCRE2_UTF is not set. This makes it 1932possible to process strings in the 16-bit UCS-2 code. This option is available 1933only if PCRE2 has been compiled with Unicode support (which is the default). 1934The PCRE2_EXTRA_CASELESS_RESTRICT option (see below) restricts caseless 1935matching such that ASCII characters match only ASCII characters and non-ASCII 1936characters match only non-ASCII characters. 1937<pre> 1938 PCRE2_UNGREEDY 1939</pre> 1940This option inverts the "greediness" of the quantifiers so that they are not 1941greedy by default, but become greedy if followed by "?". It is not compatible 1942with Perl. It can also be set by a (?U) option setting within the pattern. 1943<pre> 1944 PCRE2_USE_OFFSET_LIMIT 1945</pre> 1946This option must be set for <b>pcre2_compile()</b> if 1947<b>pcre2_set_offset_limit()</b> is going to be used to set a non-default offset 1948limit in a match context for matches that use this pattern. An error is 1949generated if an offset limit is set without this option. For more details, see 1950the description of <b>pcre2_set_offset_limit()</b> in the 1951<a href="#matchcontext">section</a> 1952that describes match contexts. See also the PCRE2_FIRSTLINE 1953option above. 1954<pre> 1955 PCRE2_UTF 1956</pre> 1957This option causes PCRE2 to regard both the pattern and the subject strings 1958that are subsequently processed as strings of UTF characters instead of 1959single-code-unit strings. It is available when PCRE2 is built to include 1960Unicode support (which is the default). If Unicode support is not available, 1961the use of this option provokes an error. Details of how PCRE2_UTF changes the 1962behaviour of PCRE2 are given in the 1963<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1964page. In particular, note that it changes the way PCRE2_CASELESS works. 1965<a name="extracompileoptions"></a></P> 1966<br><b> 1967Extra compile options 1968</b><br> 1969<P> 1970The option bits that can be set in a compile context by calling the 1971<b>pcre2_set_compile_extra_options()</b> function are as follows: 1972<pre> 1973 PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK 1974</pre> 1975Since release 10.38 PCRE2 has forbidden the use of \K within lookaround 1976assertions, following Perl's lead. This option is provided to re-enable the 1977previous behaviour (act in positive lookarounds, ignore in negative ones) in 1978case anybody is relying on it. 1979<pre> 1980 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES 1981</pre> 1982This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is 1983forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate" 1984code points in the range 0xd800 to 0xdfff are used in pairs in UTF-16 to encode 1985code points with values in the range 0x10000 to 0x10ffff. The surrogates cannot 1986therefore be represented in UTF-16. They can be represented in UTF-8 and 1987UTF-32, but are defined as invalid code points, and cause errors if encountered 1988in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2. 1989</P> 1990<P> 1991These values also cause errors if encountered in escape sequences such as 1992\x{d912} within a pattern. However, it seems that some applications, when 1993using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test 1994for the surrogates using escape sequences. The PCRE2_NO_UTF_CHECK option does 1995not disable the error that occurs, because it applies only to the testing of 1996input strings for UTF validity. 1997</P> 1998<P> 1999If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surrogate code 2000point values in UTF-8 and UTF-32 patterns no longer provoke errors and are 2001incorporated in the compiled pattern. However, they can only match subject 2002characters if the matching function is called with PCRE2_NO_UTF_CHECK set. 2003<pre> 2004 PCRE2_EXTRA_ALT_BSUX 2005</pre> 2006The original option PCRE2_ALT_BSUX causes PCRE2 to process \U, \u, and \x in 2007the way that ECMAscript (aka JavaScript) does. Additional functionality was 2008defined by ECMAscript 6; setting PCRE2_EXTRA_ALT_BSUX has the effect of 2009PCRE2_ALT_BSUX, but in addition it recognizes \u{hhh..} as a hexadecimal 2010character code, where hhh.. is any number of hexadecimal digits. 2011<pre> 2012 PCRE2_EXTRA_ASCII_BSD 2013</pre> 2014This option forces \d to match only ASCII digits, even when PCRE2_UCP is set. 2015It can be changed within a pattern by means of the (?aD) option setting. 2016<pre> 2017 PCRE2_EXTRA_ASCII_BSS 2018</pre> 2019This option forces \s to match only ASCII space characters, even when 2020PCRE2_UCP is set. It can be changed within a pattern by means of the (?aS) 2021option setting. 2022<pre> 2023 PCRE2_EXTRA_ASCII_BSW 2024</pre> 2025This option forces \w to match only ASCII word characters, even when PCRE2_UCP 2026is set. It can be changed within a pattern by means of the (?aW) option 2027setting. 2028<pre> 2029 PCRE2_EXTRA_ASCII_DIGIT 2030</pre> 2031This option forces the POSIX character classes [:digit:] and [:xdigit:] to 2032match only ASCII digits, even when PCRE2_UCP is set. It can be changed within 2033a pattern by means of the (?aT) option setting. 2034<pre> 2035 PCRE2_EXTRA_ASCII_POSIX 2036</pre> 2037This option forces all the POSIX character classes, including [:digit:] and 2038[:xdigit:], to match only ASCII characters, even when PCRE2_UCP is set. It can 2039be changed within a pattern by means of the (?aP) option setting, but note that 2040this also sets PCRE2_EXTRA_ASCII_DIGIT in order to ensure that (?-aP) unsets 2041all ASCII restrictions for POSIX classes. 2042<pre> 2043 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL 2044</pre> 2045This is a dangerous option. Use with care. By default, an unrecognized escape 2046such as \j or a malformed one such as \x{2z} causes a compile-time error when 2047detected by <b>pcre2_compile()</b>. Perl is somewhat inconsistent in handling 2048such items: for example, \j is treated as a literal "j", and non-hexadecimal 2049digits in \x{} are just ignored, though warnings are given in both cases if 2050Perl's warning switch is enabled. However, a malformed octal number after \o{ 2051always causes an error in Perl. 2052</P> 2053<P> 2054If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to 2055<b>pcre2_compile()</b>, all unrecognized or malformed escape sequences are 2056treated as single-character escapes. For example, \j is a literal "j" and 2057\x{2z} is treated as the literal string "x{2z}". Setting this option means 2058that typos in patterns may go undetected and have unexpected results. Also note 2059that a sequence such as [\N{] is interpreted as a malformed attempt at 2060[\N{...}] and so is treated as [N{] whereas [\N] gives an error because an 2061unqualified \N is a valid escape sequence but is not supported in a character 2062class. To reiterate: this is a dangerous option. Use with great care. 2063<pre> 2064 PCRE2_EXTRA_CASELESS_RESTRICT 2065</pre> 2066When either PCRE2_UCP or PCRE2_UTF is set, caseless matching follows Unicode 2067rules, which allow for more than two cases per character. There are two 2068case-equivalent character sets that contain both ASCII and non-ASCII 2069characters. The ASCII letter S is case-equivalent to U+017f (long S) and the 2070ASCII letter K is case-equivalent to U+212a (Kelvin sign). This option disables 2071recognition of case-equivalences that cross the ASCII/non-ASCII boundary. In a 2072caseless match, both characters must either be ASCII or non-ASCII. The option 2073can be changed with a pattern by the (?r) option setting. 2074<pre> 2075 PCRE2_EXTRA_ESCAPED_CR_IS_LF 2076</pre> 2077There are some legacy applications where the escape sequence \r in a pattern 2078is expected to match a newline. If this option is set, \r in a pattern is 2079converted to \n so that it matches a LF (linefeed) instead of a CR (carriage 2080return) character. The option does not affect a literal CR in the pattern, nor 2081does it affect CR specified as an explicit code point such as \x{0D}. 2082<pre> 2083 PCRE2_EXTRA_MATCH_LINE 2084</pre> 2085This option is provided for use by the <b>-x</b> option of <b>pcre2grep</b>. It 2086causes the pattern only to match complete lines. This is achieved by 2087automatically inserting the code for "^(?:" at the start of the compiled 2088pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set, the matched 2089line may be in the middle of the subject string. This option can be used with 2090PCRE2_LITERAL. 2091<pre> 2092 PCRE2_EXTRA_MATCH_WORD 2093</pre> 2094This option is provided for use by the <b>-w</b> option of <b>pcre2grep</b>. It 2095causes the pattern only to match strings that have a word boundary at the start 2096and the end. This is achieved by automatically inserting the code for "\b(?:" 2097at the start of the compiled pattern and ")\b" at the end. The option may be 2098used with PCRE2_LITERAL. However, it is ignored if PCRE2_EXTRA_MATCH_LINE is 2099also set. 2100<a name="jitcompiling"></a></P> 2101<br><a name="SEC21" href="#TOC1">JUST-IN-TIME (JIT) COMPILATION</a><br> 2102<P> 2103<b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 2104<br> 2105<br> 2106<b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2107<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2108<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2109<b> pcre2_match_context *<i>mcontext</i>);</b> 2110<br> 2111<br> 2112<b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 2113<br> 2114<br> 2115<b>pcre2_jit_stack *pcre2_jit_stack_create(size_t <i>startsize</i>,</b> 2116<b> size_t <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 2117<br> 2118<br> 2119<b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 2120<b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 2121<br> 2122<br> 2123<b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 2124</P> 2125<P> 2126These functions provide support for JIT compilation, which, if the just-in-time 2127compiler is available, further processes a compiled pattern into machine code 2128that executes much faster than the <b>pcre2_match()</b> interpretive matching 2129function. Full details are given in the 2130<a href="pcre2jit.html"><b>pcre2jit</b></a> 2131documentation. 2132</P> 2133<P> 2134JIT compilation is a heavyweight optimization. It can take some time for 2135patterns to be analyzed, and for one-off matches and simple patterns the 2136benefit of faster execution might be offset by a much slower compilation time. 2137Most (but not all) patterns can be optimized by the JIT compiler. 2138<a name="localesupport"></a></P> 2139<br><a name="SEC22" href="#TOC1">LOCALE SUPPORT</a><br> 2140<P> 2141<b>const uint8_t *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 2142<br> 2143<br> 2144<b>void pcre2_maketables_free(pcre2_general_context *<i>gcontext</i>,</b> 2145<b> const uint8_t *<i>tables</i>);</b> 2146</P> 2147<P> 2148PCRE2 handles caseless matching, and determines whether characters are letters, 2149digits, or whatever, by reference to a set of tables, indexed by character code 2150point. However, this applies only to characters whose code points are less than 2151256. By default, higher-valued code points never match escapes such as \w or 2152\d. 2153</P> 2154<P> 2155When PCRE2 is built with Unicode support (the default), certain Unicode 2156character properties can be tested with \p and \P, or, alternatively, the 2157PCRE2_UCP option can be set when a pattern is compiled; this causes \w and 2158friends to use Unicode property support instead of the built-in tables. 2159PCRE2_UCP also causes upper/lower casing operations on characters with code 2160points greater than 127 to use Unicode properties. These effects apply even 2161when PCRE2_UTF is not set. There are, however, some PCRE2_EXTRA options (see 2162above) that can be used to modify or suppress them. 2163</P> 2164<P> 2165The use of locales with Unicode is discouraged. If you are handling characters 2166with code points greater than 127, you should either use Unicode support, or 2167use locales, but not try to mix the two. 2168</P> 2169<P> 2170PCRE2 contains a built-in set of character tables that are used by default. 2171These are sufficient for many applications. Normally, the internal tables 2172recognize only ASCII characters. However, when PCRE2 is built, it is possible 2173to cause the internal tables to be rebuilt in the default "C" locale of the 2174local system, which may cause them to be different. 2175</P> 2176<P> 2177The built-in tables can be overridden by tables supplied by the application 2178that calls PCRE2. These may be created in a different locale from the default. 2179As more and more applications change to using Unicode, the need for this locale 2180support is expected to die away. 2181</P> 2182<P> 2183External tables are built by calling the <b>pcre2_maketables()</b> function, in 2184the relevant locale. The only argument to this function is a general context, 2185which can be used to pass a custom memory allocator. If the argument is NULL, 2186the system <b>malloc()</b> is used. The result can be passed to 2187<b>pcre2_compile()</b> as often as necessary, by creating a compile context and 2188calling <b>pcre2_set_character_tables()</b> to set the tables pointer therein. 2189</P> 2190<P> 2191For example, to build and use tables that are appropriate for the French locale 2192(where accented characters with values greater than 127 are treated as 2193letters), the following code could be used: 2194<pre> 2195 setlocale(LC_CTYPE, "fr_FR"); 2196 tables = pcre2_maketables(NULL); 2197 ccontext = pcre2_compile_context_create(NULL); 2198 pcre2_set_character_tables(ccontext, tables); 2199 re = pcre2_compile(..., ccontext); 2200</pre> 2201The locale name "fr_FR" is used on Linux and other Unix-like systems; if you 2202are using Windows, the name for the French locale is "french". 2203</P> 2204<P> 2205The pointer that is passed (via the compile context) to <b>pcre2_compile()</b> 2206is saved with the compiled pattern, and the same tables are used by the 2207matching functions. Thus, for any single pattern, compilation and matching both 2208happen in the same locale, but different patterns can be processed in different 2209locales. 2210</P> 2211<P> 2212It is the caller's responsibility to ensure that the memory containing the 2213tables remains available while they are still in use. When they are no longer 2214needed, you can discard them using <b>pcre2_maketables_free()</b>, which should 2215pass as its first parameter the same global context that was used to create the 2216tables. 2217</P> 2218<br><b> 2219Saving locale tables 2220</b><br> 2221<P> 2222The tables described above are just a sequence of binary bytes, which makes 2223them independent of hardware characteristics such as endianness or whether the 2224processor is 32-bit or 64-bit. A copy of the result of <b>pcre2_maketables()</b> 2225can therefore be saved in a file or elsewhere and re-used later, even in a 2226different program or on another computer. The size of the tables (number of 2227bytes) must be obtained by calling <b>pcre2_config()</b> with the 2228PCRE2_CONFIG_TABLES_LENGTH option because <b>pcre2_maketables()</b> does not 2229return this value. Note that the <b>pcre2_dftables</b> program, which is part of 2230the PCRE2 build system, can be used stand-alone to create a file that contains 2231a set of binary tables. See the 2232<a href="pcre2build.html#createtables"><b>pcre2build</b></a> 2233documentation for details. 2234<a name="infoaboutpattern"></a></P> 2235<br><a name="SEC23" href="#TOC1">INFORMATION ABOUT A COMPILED PATTERN</a><br> 2236<P> 2237<b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b> 2238</P> 2239<P> 2240The <b>pcre2_pattern_info()</b> function returns general information about a 2241compiled pattern. For information about callouts, see the 2242<a href="#infoaboutcallouts">next section.</a> 2243The first argument for <b>pcre2_pattern_info()</b> is a pointer to the compiled 2244pattern. The second argument specifies which piece of information is required, 2245and the third argument is a pointer to a variable to receive the data. If the 2246third argument is NULL, the first argument is ignored, and the function returns 2247the size in bytes of the variable that is required for the information 2248requested. Otherwise, the yield of the function is zero for success, or one of 2249the following negative numbers: 2250<pre> 2251 PCRE2_ERROR_NULL the argument <i>code</i> was NULL 2252 PCRE2_ERROR_BADMAGIC the "magic number" was not found 2253 PCRE2_ERROR_BADOPTION the value of <i>what</i> was invalid 2254 PCRE2_ERROR_UNSET the requested field is not set 2255</pre> 2256The "magic number" is placed at the start of each compiled pattern as a simple 2257check against passing an arbitrary memory pointer. Here is a typical call of 2258<b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern: 2259<pre> 2260 int rc; 2261 size_t length; 2262 rc = pcre2_pattern_info( 2263 re, /* result of pcre2_compile() */ 2264 PCRE2_INFO_SIZE, /* what is required */ 2265 &length); /* where to put the data */ 2266</pre> 2267The possible values for the second argument are defined in <b>pcre2.h</b>, and 2268are as follows: 2269<pre> 2270 PCRE2_INFO_ALLOPTIONS 2271 PCRE2_INFO_ARGOPTIONS 2272 PCRE2_INFO_EXTRAOPTIONS 2273</pre> 2274Return copies of the pattern's options. The third argument should point to a 2275<b>uint32_t</b> variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that 2276were passed to <b>pcre2_compile()</b>, whereas PCRE2_INFO_ALLOPTIONS returns 2277the compile options as modified by any top-level (*XXX) option settings such as 2278(*UTF) at the start of the pattern itself. PCRE2_INFO_EXTRAOPTIONS returns the 2279extra options that were set in the compile context by calling the 2280pcre2_set_compile_extra_options() function. 2281</P> 2282<P> 2283For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED 2284option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF. 2285Option settings such as (?i) that can change within a pattern do not affect the 2286result of PCRE2_INFO_ALLOPTIONS, even if they appear right at the start of the 2287pattern. (This was different in some earlier releases.) 2288</P> 2289<P> 2290A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if 2291the first significant item in every top-level branch is one of the following: 2292<pre> 2293 ^ unless PCRE2_MULTILINE is set 2294 \A always 2295 \G always 2296 .* sometimes - see below 2297</pre> 2298When .* is the first significant item, anchoring is possible only when all the 2299following are true: 2300<pre> 2301 .* is not in an atomic group 2302 .* is not in a capture group that is the subject of a backreference 2303 PCRE2_DOTALL is in force for .* 2304 Neither (*PRUNE) nor (*SKIP) appears in the pattern 2305 PCRE2_NO_DOTSTAR_ANCHOR is not set 2306</pre> 2307For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the 2308options returned for PCRE2_INFO_ALLOPTIONS. 2309<pre> 2310 PCRE2_INFO_BACKREFMAX 2311</pre> 2312Return the number of the highest backreference in the pattern. The third 2313argument should point to a <b>uint32_t</b> variable. Named capture groups 2314acquire numbers as well as names, and these count towards the highest 2315backreference. Backreferences such as \4 or \g{12} match the captured 2316characters of the given group, but in addition, the check that a capture 2317group is set in a conditional group such as (?(3)a|b) is also a backreference. 2318Zero is returned if there are no backreferences. 2319<pre> 2320 PCRE2_INFO_BSR 2321</pre> 2322The output is a uint32_t integer whose value indicates what character sequences 2323the \R escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R 2324matches any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means 2325that \R matches only CR, LF, or CRLF. 2326<pre> 2327 PCRE2_INFO_CAPTURECOUNT 2328</pre> 2329Return the highest capture group number in the pattern. In patterns where (?| 2330is not used, this is also the total number of capture groups. The third 2331argument should point to a <b>uint32_t</b> variable. 2332<pre> 2333 PCRE2_INFO_DEPTHLIMIT 2334</pre> 2335If the pattern set a backtracking depth limit by including an item of the form 2336(*LIMIT_DEPTH=nnnn) at the start, the value is returned. The third argument 2337should point to a uint32_t integer. If no such value has been set, the call to 2338<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2339limit will only be used during matching if it is less than the limit set or 2340defaulted by the caller of the match function. 2341<pre> 2342 PCRE2_INFO_FIRSTBITMAP 2343</pre> 2344In the absence of a single first code unit for a non-anchored pattern, 2345<b>pcre2_compile()</b> may construct a 256-bit table that defines a fixed set of 2346values for the first code unit in any match. For example, a pattern that starts 2347with [abc] results in a table with three bits set. When code unit values 2348greater than 255 are supported, the flag bit for 255 means "any code unit of 2349value 255 or above". If such a table was constructed, a pointer to it is 2350returned. Otherwise NULL is returned. The third argument should point to a 2351<b>const uint8_t *</b> variable. 2352<pre> 2353 PCRE2_INFO_FIRSTCODETYPE 2354</pre> 2355Return information about the first code unit of any matched string, for a 2356non-anchored pattern. The third argument should point to a <b>uint32_t</b> 2357variable. If there is a fixed first value, for example, the letter "c" from a 2358pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved 2359using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is 2360known that a match can occur only at the start of the subject or following a 2361newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0 2362is returned. 2363<pre> 2364 PCRE2_INFO_FIRSTCODEUNIT 2365</pre> 2366Return the value of the first code unit of any matched string for a pattern 2367where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third 2368argument should point to a <b>uint32_t</b> variable. In the 8-bit library, the 2369value is always less than 256. In the 16-bit library the value can be up to 23700xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff, 2371and up to 0xffffffff when not using UTF-32 mode. 2372<pre> 2373 PCRE2_INFO_FRAMESIZE 2374</pre> 2375Return the size (in bytes) of the data frames that are used to remember 2376backtracking positions when the pattern is processed by <b>pcre2_match()</b> 2377without the use of JIT. The third argument should point to a <b>size_t</b> 2378variable. The frame size depends on the number of capturing parentheses in the 2379pattern. Each additional capture group adds two PCRE2_SIZE variables. 2380<pre> 2381 PCRE2_INFO_HASBACKSLASHC 2382</pre> 2383Return 1 if the pattern contains any instances of \C, otherwise 0. The third 2384argument should point to a <b>uint32_t</b> variable. 2385<pre> 2386 PCRE2_INFO_HASCRORLF 2387</pre> 2388Return 1 if the pattern contains any explicit matches for CR or LF characters, 2389otherwise 0. The third argument should point to a <b>uint32_t</b> variable. An 2390explicit match is either a literal CR or LF character, or \r or \n or one of 2391the equivalent hexadecimal or octal escape sequences. 2392<pre> 2393 PCRE2_INFO_HEAPLIMIT 2394</pre> 2395If the pattern set a heap memory limit by including an item of the form 2396(*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argument 2397should point to a uint32_t integer. If no such value has been set, the call to 2398<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2399limit will only be used during matching if it is less than the limit set or 2400defaulted by the caller of the match function. 2401<pre> 2402 PCRE2_INFO_JCHANGED 2403</pre> 2404Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise 24050. The third argument should point to a <b>uint32_t</b> variable. (?J) and 2406(?-J) set and unset the local PCRE2_DUPNAMES option, respectively. 2407<pre> 2408 PCRE2_INFO_JITSIZE 2409</pre> 2410If the compiled pattern was successfully processed by 2411<b>pcre2_jit_compile()</b>, return the size of the JIT compiled code, otherwise 2412return zero. The third argument should point to a <b>size_t</b> variable. 2413<pre> 2414 PCRE2_INFO_LASTCODETYPE 2415</pre> 2416Returns 1 if there is a rightmost literal code unit that must exist in any 2417matched string, other than at its start. The third argument should point to a 2418<b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is 2419returned, the code unit value itself can be retrieved using 2420PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is 2421recorded only if it follows something of variable length. For example, for the 2422pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned from 2423PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0. 2424<pre> 2425 PCRE2_INFO_LASTCODEUNIT 2426</pre> 2427Return the value of the rightmost literal code unit that must exist in any 2428matched string, other than at its start, for a pattern where 2429PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argument 2430should point to a <b>uint32_t</b> variable. 2431<pre> 2432 PCRE2_INFO_MATCHEMPTY 2433</pre> 2434Return 1 if the pattern might match an empty string, otherwise 0. The third 2435argument should point to a <b>uint32_t</b> variable. When a pattern contains 2436recursive subroutine calls it is not always possible to determine whether or 2437not it can match an empty string. PCRE2 takes a cautious approach and returns 1 2438in such cases. 2439<pre> 2440 PCRE2_INFO_MATCHLIMIT 2441</pre> 2442If the pattern set a match limit by including an item of the form 2443(*LIMIT_MATCH=nnnn) at the start, the value is returned. The third argument 2444should point to a uint32_t integer. If no such value has been set, the call to 2445<b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2446limit will only be used during matching if it is less than the limit set or 2447defaulted by the caller of the match function. 2448<pre> 2449 PCRE2_INFO_MAXLOOKBEHIND 2450</pre> 2451A lookbehind assertion moves back a certain number of characters (not code 2452units) when it starts to process each of its branches. This request returns the 2453largest of these backward moves. The third argument should point to a uint32_t 2454integer. The simple assertions \b and \B require a one-character lookbehind 2455and cause PCRE2_INFO_MAXLOOKBEHIND to return 1 in the absence of anything 2456longer. \A also registers a one-character lookbehind, though it does not 2457actually inspect the previous character. 2458</P> 2459<P> 2460Note that this information is useful for multi-segment matching only 2461if the pattern contains no nested lookbehinds. For example, the pattern 2462(?<=a(?<=ba)c) returns a maximum lookbehind of 2, but when it is processed, the 2463first lookbehind moves back by two characters, matches one character, then the 2464nested lookbehind also moves back by two characters. This puts the matching 2465point three characters earlier than it was at the start. 2466PCRE2_INFO_MAXLOOKBEHIND is really only useful as a debugging tool. See the 2467<a href="pcre2partial.html"><b>pcre2partial</b></a> 2468documentation for a discussion of multi-segment matching. 2469<pre> 2470 PCRE2_INFO_MINLENGTH 2471</pre> 2472If a minimum length for matching subject strings was computed, its value is 2473returned. Otherwise the returned value is 0. This value is not computed when 2474PCRE2_NO_START_OPTIMIZE is set. The value is a number of characters, which in 2475UTF mode may be different from the number of code units. The third argument 2476should point to a <b>uint32_t</b> variable. The value is a lower bound to the 2477length of any matching string. There may not be any strings of that length that 2478do actually match, but every string that does match is at least that long. 2479<pre> 2480 PCRE2_INFO_NAMECOUNT 2481 PCRE2_INFO_NAMEENTRYSIZE 2482 PCRE2_INFO_NAMETABLE 2483</pre> 2484PCRE2 supports the use of named as well as numbered capturing parentheses. The 2485names are just an additional way of identifying the parentheses, which still 2486acquire numbers. Several convenience functions such as 2487<b>pcre2_substring_get_byname()</b> are provided for extracting captured 2488substrings by name. It is also possible to extract the data directly, by first 2489converting the name to a number in order to access the correct pointers in the 2490output vector (described with <b>pcre2_match()</b> below). To do the conversion, 2491you need to use the name-to-number map, which is described by these three 2492values. 2493</P> 2494<P> 2495The map consists of a number of fixed-size entries. PCRE2_INFO_NAMECOUNT gives 2496the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each 2497entry in code units; both of these return a <b>uint32_t</b> value. The entry 2498size depends on the length of the longest name. 2499</P> 2500<P> 2501PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is 2502a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, the first 2503two bytes of each entry are the number of the capturing parenthesis, most 2504significant byte first. In the 16-bit library, the pointer points to 16-bit 2505code units, the first of which contains the parenthesis number. In the 32-bit 2506library, the pointer points to 32-bit code units, the first of which contains 2507the parenthesis number. The rest of the entry is the corresponding name, zero 2508terminated. 2509</P> 2510<P> 2511The names are in alphabetical order. If (?| is used to create multiple capture 2512groups with the same number, as described in the 2513<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 2514in the 2515<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2516page, the groups may be given the same name, but there is only one entry in the 2517table. Different names for groups of the same number are not permitted. 2518</P> 2519<P> 2520Duplicate names for capture groups with different numbers are permitted, but 2521only if PCRE2_DUPNAMES is set. They appear in the table in the order in which 2522they were found in the pattern. In the absence of (?| this is the order of 2523increasing number; when (?| is used this is not necessarily the case because 2524later capture groups may have lower numbers. 2525</P> 2526<P> 2527As a simple example of the name/number table, consider the following pattern 2528after compilation by the 8-bit library (assume PCRE2_EXTENDED is set, so white 2529space - including newlines - is ignored): 2530<pre> 2531 (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) 2532</pre> 2533There are four named capture groups, so the table has four entries, and each 2534entry in the table is eight bytes long. The table is as follows, with 2535non-printing bytes shows in hexadecimal, and undefined bytes shown as ??: 2536<pre> 2537 00 01 d a t e 00 ?? 2538 00 05 d a y 00 ?? ?? 2539 00 04 m o n t h 00 2540 00 02 y e a r 00 ?? 2541</pre> 2542When writing code to extract data from named capture groups using the 2543name-to-number map, remember that the length of the entries is likely to be 2544different for each compiled pattern. 2545<pre> 2546 PCRE2_INFO_NEWLINE 2547</pre> 2548The output is one of the following <b>uint32_t</b> values: 2549<pre> 2550 PCRE2_NEWLINE_CR Carriage return (CR) 2551 PCRE2_NEWLINE_LF Linefeed (LF) 2552 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 2553 PCRE2_NEWLINE_ANY Any Unicode line ending 2554 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 2555 PCRE2_NEWLINE_NUL The NUL character (binary zero) 2556</pre> 2557This identifies the character sequence that will be recognized as meaning 2558"newline" while matching. 2559<pre> 2560 PCRE2_INFO_SIZE 2561</pre> 2562Return the size of the compiled pattern in bytes (for all three libraries). The 2563third argument should point to a <b>size_t</b> variable. This value includes the 2564size of the general data block that precedes the code units of the compiled 2565pattern itself. The value that is used when <b>pcre2_compile()</b> is getting 2566memory in which to place the compiled pattern may be slightly larger than the 2567value returned by this option, because there are cases where the code that 2568calculates the size has to over-estimate. Processing a pattern with the JIT 2569compiler does not alter the value returned by this option. 2570<a name="infoaboutcallouts"></a></P> 2571<br><a name="SEC24" href="#TOC1">INFORMATION ABOUT A PATTERN'S CALLOUTS</a><br> 2572<P> 2573<b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 2574<b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 2575<b> void *<i>user_data</i>);</b> 2576<br> 2577<br> 2578A script language that supports the use of string arguments in callouts might 2579like to scan all the callouts in a pattern before running the match. This can 2580be done by calling <b>pcre2_callout_enumerate()</b>. The first argument is a 2581pointer to a compiled pattern, the second points to a callback function, and 2582the third is arbitrary user data. The callback function is called for every 2583callout in the pattern in the order in which they appear. Its first argument is 2584a pointer to a callout enumeration block, and its second argument is the 2585<i>user_data</i> value that was passed to <b>pcre2_callout_enumerate()</b>. The 2586contents of the callout enumeration block are described in the 2587<a href="pcre2callout.html"><b>pcre2callout</b></a> 2588documentation, which also gives further details about callouts. 2589</P> 2590<br><a name="SEC25" href="#TOC1">SERIALIZATION AND PRECOMPILING</a><br> 2591<P> 2592It is possible to save compiled patterns on disc or elsewhere, and reload them 2593later, subject to a number of restrictions. The host on which the patterns are 2594reloaded must be running the same version of PCRE2, with the same code unit 2595width, and must also have the same endianness, pointer width, and PCRE2_SIZE 2596type. Before compiled patterns can be saved, they must be converted to a 2597"serialized" form, which in the case of PCRE2 is really just a bytecode dump. 2598The functions whose names begin with <b>pcre2_serialize_</b> are used for 2599converting to and from the serialized form. They are described in the 2600<a href="pcre2serialize.html"><b>pcre2serialize</b></a> 2601documentation. Note that PCRE2 serialization does not convert compiled patterns 2602to an abstract format like Java or .NET serialization. 2603<a name="matchdatablock"></a></P> 2604<br><a name="SEC26" href="#TOC1">THE MATCH DATA BLOCK</a><br> 2605<P> 2606<b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 2607<b> pcre2_general_context *<i>gcontext</i>);</b> 2608<br> 2609<br> 2610<b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 2611<b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 2612<br> 2613<br> 2614<b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 2615</P> 2616<P> 2617Information about a successful or unsuccessful match is placed in a match 2618data block, which is an opaque structure that is accessed by function calls. In 2619particular, the match data block contains a vector of offsets into the subject 2620string that define the matched parts of the subject. This is known as the 2621<i>ovector</i>. 2622</P> 2623<P> 2624Before calling <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or 2625<b>pcre2_jit_match()</b> you must create a match data block by calling one of 2626the creation functions above. For <b>pcre2_match_data_create()</b>, the first 2627argument is the number of pairs of offsets in the <i>ovector</i>. 2628</P> 2629<P> 2630When using <b>pcre2_match()</b>, one pair of offsets is required to identify the 2631string that matched the whole pattern, with an additional pair for each 2632captured substring. For example, a value of 4 creates enough space to record 2633the matched portion of the subject plus three captured substrings. 2634</P> 2635<P> 2636When using <b>pcre2_dfa_match()</b> there may be multiple matched substrings of 2637different lengths at the same point in the subject. The ovector should be made 2638large enough to hold as many as are expected. 2639</P> 2640<P> 2641A minimum of at least 1 pair is imposed by <b>pcre2_match_data_create()</b>, so 2642it is always possible to return the overall matched string in the case of 2643<b>pcre2_match()</b> or the longest match in the case of 2644<b>pcre2_dfa_match()</b>. The maximum number of pairs is 65535; if the first 2645argument of <b>pcre2_match_data_create()</b> is greater than this, 65535 is 2646used. 2647</P> 2648<P> 2649The second argument of <b>pcre2_match_data_create()</b> is a pointer to a 2650general context, which can specify custom memory management for obtaining the 2651memory for the match data block. If you are not using custom memory management, 2652pass NULL, which causes <b>malloc()</b> to be used. 2653</P> 2654<P> 2655For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a 2656pointer to a compiled pattern. The ovector is created to be exactly the right 2657size to hold all the substrings a pattern might capture when matched using 2658<b>pcre2_match()</b>. You should not use this call when matching with 2659<b>pcre2_dfa_match()</b>. The second argument is again a pointer to a general 2660context, but in this case if NULL is passed, the memory is obtained using the 2661same allocator that was used for the compiled pattern (custom or default). 2662</P> 2663<P> 2664A match data block can be used many times, with the same or different compiled 2665patterns. You can extract information from a match data block after a match 2666operation has finished, using functions that are described in the sections on 2667<a href="#matchedstrings">matched strings</a> 2668and 2669<a href="#matchotherdata">other match data</a> 2670below. 2671</P> 2672<P> 2673When a call of <b>pcre2_match()</b> fails, valid data is available in the match 2674block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one 2675of the error codes for an invalid UTF string. Exactly what is available depends 2676on the error, and is detailed below. 2677</P> 2678<P> 2679When one of the matching functions is called, pointers to the compiled pattern 2680and the subject string are set in the match data block so that they can be 2681referenced by the extraction functions after a successful match. After running 2682a match, you must not free a compiled pattern or a subject string until after 2683all operations on the match data block (for that match) have taken place, 2684unless, in the case of the subject string, you have used the 2685PCRE2_COPY_MATCHED_SUBJECT option, which is described in the section entitled 2686"Option bits for <b>pcre2_match()</b>" 2687<a href="#matchoptions>">below.</a> 2688</P> 2689<P> 2690When a match data block itself is no longer needed, it should be freed by 2691calling <b>pcre2_match_data_free()</b>. If this function is called with a NULL 2692argument, it returns immediately, without doing anything. 2693</P> 2694<br><a name="SEC27" href="#TOC1">MEMORY USE FOR MATCH DATA BLOCKS</a><br> 2695<P> 2696<b>PCRE2_SIZE pcre2_get_match_data_size(pcre2_match_data *<i>match_data</i>);</b> 2697<br> 2698<br> 2699<b>PCRE2_SIZE pcre2_get_match_data_heapframes_size(</b> 2700<b> pcre2_match_data *<i>match_data</i>);</b> 2701</P> 2702<P> 2703The size of a match data block depends on the size of the ovector that it 2704contains. The function <b>pcre2_get_match_data_size()</b> returns the size, in 2705bytes, of the block that is its argument. 2706</P> 2707<P> 2708When <b>pcre2_match()</b> runs interpretively (that is, without using JIT), it 2709makes use of a vector of data frames for remembering backtracking positions. 2710The size of each individual frame depends on the number of capturing 2711parentheses in the pattern and can be obtained by calling 2712<b>pcre2_pattern_info()</b> with the PCRE2_INFO_FRAMESIZE option (see the 2713section entitled "Information about a compiled pattern" 2714<a href="#infoaboutpattern>">above).</a> 2715</P> 2716<P> 2717Heap memory is used for the frames vector; if the initial memory block turns 2718out to be too small during matching, it is automatically expanded. When 2719<b>pcre2_match()</b> returns, the memory is not freed, but remains attached to 2720the match data block, for use by any subsequent matches that use the same 2721block. It is automatically freed when the match data block itself is freed. 2722</P> 2723<P> 2724You can find the current size of the frames vector that a match data block owns 2725by calling <b>pcre2_get_match_data_heapframes_size()</b>. For a newly created 2726match data block the size will be zero. Some types of match may require a lot 2727of frames and thus a large vector; applications that run in environments where 2728memory is constrained can check this and free the match data block if the heap 2729frames vector has become too big. 2730</P> 2731<br><a name="SEC28" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> 2732<P> 2733<b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2734<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2735<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2736<b> pcre2_match_context *<i>mcontext</i>);</b> 2737</P> 2738<P> 2739The function <b>pcre2_match()</b> is called to match a subject string against a 2740compiled pattern, which is passed in the <i>code</i> argument. You can call 2741<b>pcre2_match()</b> with the same <i>code</i> argument as many times as you 2742like, in order to find multiple matches in the subject string or to match 2743different subject strings with the same pattern. 2744</P> 2745<P> 2746This function is the main matching facility of the library, and it operates in 2747a Perl-like manner. For specialist use there is also an alternative matching 2748function, which is described 2749<a href="#dfamatch">below</a> 2750in the section about the <b>pcre2_dfa_match()</b> function. 2751</P> 2752<P> 2753Here is an example of a simple call to <b>pcre2_match()</b>: 2754<pre> 2755 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 2756 int rc = pcre2_match( 2757 re, /* result of pcre2_compile() */ 2758 "some string", /* the subject string */ 2759 11, /* the length of the subject string */ 2760 0, /* start at offset 0 in the subject */ 2761 0, /* default options */ 2762 md, /* the match data block */ 2763 NULL); /* a match context; NULL means use defaults */ 2764</pre> 2765If the subject string is zero-terminated, the length can be given as 2766PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common 2767matching parameters are to be changed. For details, see the section on 2768<a href="#matchcontext">the match context</a> 2769above. 2770</P> 2771<br><b> 2772The string to be matched by <b>pcre2_match()</b> 2773</b><br> 2774<P> 2775The subject string is passed to <b>pcre2_match()</b> as a pointer in 2776<i>subject</i>, a length in <i>length</i>, and a starting offset in 2777<i>startoffset</i>. The length and offset are in code units, not characters. 2778That is, they are in bytes for the 8-bit library, 16-bit code units for the 277916-bit library, and 32-bit code units for the 32-bit library, whether or not 2780UTF processing is enabled. As a special case, if <i>subject</i> is NULL and 2781<i>length</i> is zero, the subject is assumed to be an empty string. If 2782<i>length</i> is non-zero, an error occurs if <i>subject</i> is NULL. 2783</P> 2784<P> 2785If <i>startoffset</i> is greater than the length of the subject, 2786<b>pcre2_match()</b> returns PCRE2_ERROR_BADOFFSET. When the starting offset is 2787zero, the search for a match starts at the beginning of the subject, and this 2788is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset 2789must point to the start of a character, or to the end of the subject (in UTF-32 2790mode, one code unit equals one character, so all offsets are valid). Like the 2791pattern string, the subject may contain binary zeros. 2792</P> 2793<P> 2794A non-zero starting offset is useful when searching for another match in the 2795same subject by calling <b>pcre2_match()</b> again after a previous success. 2796Setting <i>startoffset</i> differs from passing over a shortened string and 2797setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of 2798lookbehind. For example, consider the pattern 2799<pre> 2800 \Biss\B 2801</pre> 2802which finds occurrences of "iss" in the middle of words. (\B matches only if 2803the current position in the subject is not a word boundary.) When applied to 2804the string "Mississippi" the first call to <b>pcre2_match()</b> finds the first 2805occurrence. If <b>pcre2_match()</b> is called again with just the remainder of 2806the subject, namely "issippi", it does not match, because \B is always false 2807at the start of the subject, which is deemed to be a word boundary. However, if 2808<b>pcre2_match()</b> is passed the entire string again, but with 2809<i>startoffset</i> set to 4, it finds the second occurrence of "iss" because it 2810is able to look behind the starting point to discover that it is preceded by a 2811letter. 2812</P> 2813<P> 2814Finding all the matches in a subject is tricky when the pattern can match an 2815empty string. It is possible to emulate Perl's /g behaviour by first trying the 2816match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and 2817PCRE2_ANCHORED options, and then if that fails, advancing the starting offset 2818and trying an ordinary match again. There is some code that demonstrates how to 2819do this in the 2820<a href="pcre2demo.html"><b>pcre2demo</b></a> 2821sample program. In the most general case, you have to check to see if the 2822newline convention recognizes CRLF as a newline, and if so, and the current 2823character is CR followed by LF, advance the starting offset by two characters 2824instead of one. 2825</P> 2826<P> 2827If a non-zero starting offset is passed when the pattern is anchored, a single 2828attempt to match at the given offset is made. This can only succeed if the 2829pattern does not require the match to be at the start of the subject. In other 2830words, the anchoring must be the result of setting the PCRE2_ANCHORED option or 2831the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. 2832<a name="matchoptions"></a></P> 2833<br><b> 2834Option bits for <b>pcre2_match()</b> 2835</b><br> 2836<P> 2837The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be 2838zero. The only bits that may be set are PCRE2_ANCHORED, 2839PCRE2_COPY_MATCHED_SUBJECT, PCRE2_DISABLE_RECURSELOOP_CHECK, PCRE2_ENDANCHORED, 2840PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, 2841PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. 2842Their action is described below. 2843</P> 2844<P> 2845Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not supported by 2846the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the 2847interpretive code in <b>pcre2_match()</b> is run. 2848PCRE2_DISABLE_RECURSELOOP_CHECK is ignored by JIT, but apart from PCRE2_NO_JIT 2849(obviously), the remaining options are supported for JIT matching. 2850<pre> 2851 PCRE2_ANCHORED 2852</pre> 2853The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first 2854matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out 2855to be anchored by virtue of its contents, it cannot be made unachored at 2856matching time. Note that setting the option at match time disables JIT 2857matching. 2858<pre> 2859 PCRE2_COPY_MATCHED_SUBJECT 2860</pre> 2861By default, a pointer to the subject is remembered in the match data block so 2862that, after a successful match, it can be referenced by the substring 2863extraction functions. This means that the subject's memory must not be freed 2864until all such operations are complete. For some applications where the 2865lifetime of the subject string is not guaranteed, it may be necessary to make a 2866copy of the subject string, but it is wasteful to do this unless the match is 2867successful. After a successful match, if PCRE2_COPY_MATCHED_SUBJECT is set, the 2868subject is copied and the new pointer is remembered in the match data block 2869instead of the original subject pointer. The memory allocator that was used for 2870the match block itself is used. The copy is automatically freed when 2871<b>pcre2_match_data_free()</b> is called to free the match data block. It is also 2872automatically freed if the match data block is re-used for another match 2873operation. 2874<pre> 2875 PCRE2_DISABLE_RECURSELOOP_CHECK 2876</pre> 2877This option is relevant only to <b>pcre2_match()</b> for interpretive matching. 2878It is ignored when JIT is used, and is forbidden for <b>pcre2_dfa_match()</b>. 2879</P> 2880<P> 2881The use of recursion in patterns can lead to infinite loops. In the 2882interpretive matcher these would be eventually caught by the match or heap 2883limits, but this could take a long time and/or use a lot of memory if the 2884limits are large. There is therefore a check at the start of each recursion. 2885If the same group is still active from a previous call, and the current subject 2886pointer is the same as it was at the start of that group, and the furthest 2887inspected character of the subject has not changed, an error is generated. 2888</P> 2889<P> 2890There are rare cases of matches that would complete, but nevertheless trigger 2891this error. This option disables the check. It is provided mainly for testing 2892when comparing JIT and interpretive behaviour. 2893<pre> 2894 PCRE2_ENDANCHORED 2895</pre> 2896If the PCRE2_ENDANCHORED option is set, any string that <b>pcre2_match()</b> 2897matches must be right at the end of the subject string. Note that setting the 2898option at match time disables JIT matching. 2899<pre> 2900 PCRE2_NOTBOL 2901</pre> 2902This option specifies that first character of the subject string is not the 2903beginning of a line, so the circumflex metacharacter should not match before 2904it. Setting this without having set PCRE2_MULTILINE at compile time causes 2905circumflex never to match. This option affects only the behaviour of the 2906circumflex metacharacter. It does not affect \A. 2907<pre> 2908 PCRE2_NOTEOL 2909</pre> 2910This option specifies that the end of the subject string is not the end of a 2911line, so the dollar metacharacter should not match it nor (except in multiline 2912mode) a newline immediately before it. Setting this without having set 2913PCRE2_MULTILINE at compile time causes dollar never to match. This option 2914affects only the behaviour of the dollar metacharacter. It does not affect \Z 2915or \z. 2916<pre> 2917 PCRE2_NOTEMPTY 2918</pre> 2919An empty string is not considered to be a valid match if this option is set. If 2920there are alternatives in the pattern, they are tried. If all the alternatives 2921match the empty string, the entire match fails. For example, if the pattern 2922<pre> 2923 a?b? 2924</pre> 2925is applied to a string not beginning with "a" or "b", it matches an empty 2926string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not 2927valid, so <b>pcre2_match()</b> searches further into the string for occurrences 2928of "a" or "b". 2929<pre> 2930 PCRE2_NOTEMPTY_ATSTART 2931</pre> 2932This is like PCRE2_NOTEMPTY, except that it locks out an empty string match 2933only at the first matching position, that is, at the start of the subject plus 2934the starting offset. An empty string match later in the subject is permitted. 2935If the pattern is anchored, such a match can occur only if the pattern contains 2936\K. 2937<pre> 2938 PCRE2_NO_JIT 2939</pre> 2940By default, if a pattern has been successfully processed by 2941<b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b> 2942is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use 2943of JIT; it forces matching to be done by the interpreter. 2944<pre> 2945 PCRE2_NO_UTF_CHECK 2946</pre> 2947When PCRE2_UTF is set at compile time, the validity of the subject as a UTF 2948string is checked unless PCRE2_NO_UTF_CHECK is passed to <b>pcre2_match()</b> or 2949PCRE2_MATCH_INVALID_UTF was passed to <b>pcre2_compile()</b>. The latter special 2950case is discussed in detail in the 2951<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2952documentation. 2953</P> 2954<P> 2955In the default case, if a non-zero starting offset is given, the check is 2956applied only to that part of the subject that could be inspected during 2957matching, and there is a check that the starting offset points to the first 2958code unit of a character or to the end of the subject. If there are no 2959lookbehind assertions in the pattern, the check starts at the starting offset. 2960Otherwise, it starts at the length of the longest lookbehind before the 2961starting offset, or at the start of the subject if there are not that many 2962characters before the starting offset. Note that the sequences \b and \B are 2963one-character lookbehinds. 2964</P> 2965<P> 2966The check is carried out before any other processing takes place, and a 2967negative error code is returned if the check fails. There are several UTF error 2968codes for each code unit width, corresponding to different problems with the 2969code unit sequence. There are discussions about the validity of 2970<a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 2971<a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 2972and 2973<a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 2974in the 2975<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2976documentation. 2977</P> 2978<P> 2979If you know that your subject is valid, and you want to skip this check for 2980performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling 2981<b>pcre2_match()</b>. You might want to do this for the second and subsequent 2982calls to <b>pcre2_match()</b> if you are making repeated calls to find multiple 2983matches in the same subject string. 2984</P> 2985<P> 2986<b>Warning:</b> Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when 2987PCRE2_NO_UTF_CHECK is set at match time the effect of passing an invalid 2988string as a subject, or an invalid value of <i>startoffset</i>, is undefined. 2989Your program may crash or loop indefinitely or give wrong results. 2990<pre> 2991 PCRE2_PARTIAL_HARD 2992 PCRE2_PARTIAL_SOFT 2993</pre> 2994These options turn on the partial matching feature. A partial match occurs if 2995the end of the subject string is reached successfully, but there are not enough 2996subject characters to complete the match. In addition, either at least one 2997character must have been inspected or the pattern must contain a lookbehind, or 2998the pattern must be one that could match an empty string. 2999</P> 3000<P> 3001If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) 3002is set, matching continues by testing any remaining alternatives. Only if no 3003complete match can be found is PCRE2_ERROR_PARTIAL returned instead of 3004PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that the 3005caller is prepared to handle a partial match, but only if no complete match can 3006be found. 3007</P> 3008<P> 3009If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if 3010a partial match is found, <b>pcre2_match()</b> immediately returns 3011PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other 3012words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more 3013important that an alternative complete match. 3014</P> 3015<P> 3016There is a more detailed discussion of partial and multi-segment matching, with 3017examples, in the 3018<a href="pcre2partial.html"><b>pcre2partial</b></a> 3019documentation. 3020</P> 3021<br><a name="SEC29" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br> 3022<P> 3023When PCRE2 is built, a default newline convention is set; this is usually the 3024standard convention for the operating system. The default can be overridden in 3025a 3026<a href="#compilecontext">compile context</a> 3027by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a 3028pattern string with, for example, (*CRLF), as described in the 3029<a href="pcre2pattern.html#newlines">section on newline conventions</a> 3030in the 3031<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3032page. During matching, the newline choice affects the behaviour of the dot, 3033circumflex, and dollar metacharacters. It may also alter the way the match 3034starting position is advanced after a match failure for an unanchored pattern. 3035</P> 3036<P> 3037When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as 3038the newline convention, and a match attempt for an unanchored pattern fails 3039when the current starting position is at a CRLF sequence, and the pattern 3040contains no explicit matches for CR or LF characters, the match position is 3041advanced by two characters instead of one, in other words, to after the CRLF. 3042</P> 3043<P> 3044The above rule is a compromise that makes the most common cases work as 3045expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is 3046not set), it does not match the string "\r\nA" because, after failing at the 3047start, it skips both the CR and the LF before retrying. However, the pattern 3048[\r\n]A does match that string, because it contains an explicit CR or LF 3049reference, and so advances only by one character after the first failure. 3050</P> 3051<P> 3052An explicit match for CR of LF is either a literal appearance of one of those 3053characters in the pattern, or one of the \r or \n or equivalent octal or 3054hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor 3055does \s, even though it includes CR and LF in the characters that it matches. 3056</P> 3057<P> 3058Notwithstanding the above, anomalous effects may still occur when CRLF is a 3059valid newline sequence and explicit \r or \n escapes appear in the pattern. 3060<a name="matchedstrings"></a></P> 3061<br><a name="SEC30" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br> 3062<P> 3063<b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 3064<br> 3065<br> 3066<b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 3067</P> 3068<P> 3069In general, a pattern matches a certain portion of the subject, and in 3070addition, further substrings from the subject may be picked out by 3071parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's 3072book, this is called "capturing" in what follows, and the phrase "capture 3073group" (Perl terminology) is used for a fragment of a pattern that picks out a 3074substring. PCRE2 supports several other kinds of parenthesized group that do 3075not cause substrings to be captured. The <b>pcre2_pattern_info()</b> function 3076can be used to find out how many capture groups there are in a compiled 3077pattern. 3078</P> 3079<P> 3080You can use auxiliary functions for accessing captured substrings 3081<a href="#extractbynumber">by number</a> 3082or 3083<a href="#extractbyname">by name,</a> 3084as described in sections below. 3085</P> 3086<P> 3087Alternatively, you can make direct use of the vector of PCRE2_SIZE values, 3088called the <b>ovector</b>, which contains the offsets of captured strings. It is 3089part of the 3090<a href="#matchdatablock">match data block.</a> 3091The function <b>pcre2_get_ovector_pointer()</b> returns the address of the 3092ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of 3093values it contains. 3094</P> 3095<P> 3096Within the ovector, the first in each pair of values is set to the offset of 3097the first code unit of a substring, and the second is set to the offset of the 3098first code unit after the end of a substring. These values are always code unit 3099offsets, not character offsets. That is, they are byte offsets in the 8-bit 3100library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit 3101library. 3102</P> 3103<P> 3104After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair 3105of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They 3106identify the part of the subject that was partially matched. See the 3107<a href="pcre2partial.html"><b>pcre2partial</b></a> 3108documentation for details of partial matching. 3109</P> 3110<P> 3111After a fully successful match, the first pair of offsets identifies the 3112portion of the subject string that was matched by the entire pattern. The next 3113pair is used for the first captured substring, and so on. The value returned by 3114<b>pcre2_match()</b> is one more than the highest numbered pair that has been 3115set. For example, if two substrings have been captured, the returned value is 31163. If there are no captured substrings, the return value from a successful 3117match is 1, indicating that just the first pair of offsets has been set. 3118</P> 3119<P> 3120If a pattern uses the \K escape sequence within a positive assertion, the 3121reported start of a successful match can be greater than the end of the match. 3122For example, if the pattern (?=ab\K) is matched against "ab", the start and 3123end offset values for the match are 2 and 0. 3124</P> 3125<P> 3126If a capture group is matched repeatedly within a single match operation, it is 3127the last portion of the subject that it matched that is returned. 3128</P> 3129<P> 3130If the ovector is too small to hold all the captured substring offsets, as much 3131as possible is filled in, and the function returns a value of zero. If captured 3132substrings are not of interest, <b>pcre2_match()</b> may be called with a match 3133data block whose ovector is of minimum length (that is, one pair). 3134</P> 3135<P> 3136It is possible for capture group number <i>n+1</i> to match some part of the 3137subject when group <i>n</i> has not been used at all. For example, if the string 3138"abc" is matched against the pattern (a|(z))(bc) the return from the function 3139is 4, and groups 1 and 3 are matched, but 2 is not. When this happens, both 3140values in the offset pairs corresponding to unused groups are set to 3141PCRE2_UNSET. 3142</P> 3143<P> 3144Offset values that correspond to unused groups at the end of the expression are 3145also set to PCRE2_UNSET. For example, if the string "abc" is matched against 3146the pattern (abc)(x(yz)?)? groups 2 and 3 are not matched. The return from the 3147function is 2, because the highest used capture group number is 1. The offsets 3148for the second and third capture groups (assuming the vector is large enough, 3149of course) are set to PCRE2_UNSET. 3150</P> 3151<P> 3152Elements in the ovector that do not correspond to capturing parentheses in the 3153pattern are never changed. That is, if a pattern contains <i>n</i> capturing 3154parentheses, no more than <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by 3155<b>pcre2_match()</b>. The other elements retain whatever values they previously 3156had. After a failed match attempt, the contents of the ovector are unchanged. 3157<a name="matchotherdata"></a></P> 3158<br><a name="SEC31" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br> 3159<P> 3160<b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 3161<br> 3162<br> 3163<b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 3164</P> 3165<P> 3166As well as the offsets in the ovector, other information about a match is 3167retained in the match data block and can be retrieved by the above functions in 3168appropriate circumstances. If they are called at other times, the result is 3169undefined. 3170</P> 3171<P> 3172After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure 3173to match (PCRE2_ERROR_NOMATCH), a mark name may be available. The function 3174<b>pcre2_get_mark()</b> can be called to access this name, which can be 3175specified in the pattern by any of the backtracking control verbs, not just 3176(*MARK). The same function applies to all the verbs. It returns a pointer to 3177the zero-terminated name, which is within the compiled pattern. If no name is 3178available, NULL is returned. The length of the name (excluding the terminating 3179zero) is stored in the code unit that precedes the name. You should use this 3180length instead of relying on the terminating zero if the name might contain a 3181binary zero. 3182</P> 3183<P> 3184After a successful match, the name that is returned is the last mark name 3185encountered on the matching path through the pattern. Instances of backtracking 3186verbs without names do not count. Thus, for example, if the matching path 3187contains (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a 3188partial match, the last encountered name is returned. For example, consider 3189this pattern: 3190<pre> 3191 ^(*MARK:A)((*MARK:B)a|b)c 3192</pre> 3193When it matches "bc", the returned name is A. The B mark is "seen" in the first 3194branch of the group, but it is not on the matching path. On the other hand, 3195when this pattern fails to match "bx", the returned name is B. 3196</P> 3197<P> 3198<b>Warning:</b> By default, certain start-of-match optimizations are used to 3199give a fast "no match" result in some situations. For example, if the anchoring 3200is removed from the pattern above, there is an initial check for the presence 3201of "c" in the subject before running the matching engine. This check fails for 3202"bx", causing a match failure without seeing any marks. You can disable the 3203start-of-match optimizations by setting the PCRE2_NO_START_OPTIMIZE option for 3204<b>pcre2_compile()</b> or by starting the pattern with (*NO_START_OPT). 3205</P> 3206<P> 3207After a successful match, a partial match, or one of the invalid UTF errors 3208(for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be 3209called. After a successful or partial match it returns the code unit offset of 3210the character at which the match started. For a non-partial match, this can be 3211different to the value of <i>ovector[0]</i> if the pattern contains the \K 3212escape sequence. After a partial match, however, this value is always the same 3213as <i>ovector[0]</i> because \K does not affect the result of a partial match. 3214</P> 3215<P> 3216After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain 3217the code unit offset of the invalid UTF character. Details are given in the 3218<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3219page. 3220<a name="errorlist"></a></P> 3221<br><a name="SEC32" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br> 3222<P> 3223If <b>pcre2_match()</b> fails, it returns a negative number. This can be 3224converted to a text string by calling the <b>pcre2_get_error_message()</b> 3225function (see "Obtaining a textual error message" 3226<a href="#geterrormessage">below).</a> 3227Negative error codes are also returned by other functions, and are documented 3228with them. The codes are given names in the header file. If UTF checking is in 3229force and an invalid UTF subject string is detected, one of a number of 3230UTF-specific negative error codes is returned. Details are given in the 3231<a href="pcre2unicode.html"><b>pcre2unicode</b></a> 3232page. The following are the other errors that may be returned by 3233<b>pcre2_match()</b>: 3234<pre> 3235 PCRE2_ERROR_NOMATCH 3236</pre> 3237The subject string did not match the pattern. 3238<pre> 3239 PCRE2_ERROR_PARTIAL 3240</pre> 3241The subject string did not match, but it did match partially. See the 3242<a href="pcre2partial.html"><b>pcre2partial</b></a> 3243documentation for details of partial matching. 3244<pre> 3245 PCRE2_ERROR_BADMAGIC 3246</pre> 3247PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to 3248catch the case when it is passed a junk pointer. This is the error that is 3249returned when the magic number is not present. 3250<pre> 3251 PCRE2_ERROR_BADMODE 3252</pre> 3253This error is given when a compiled pattern is passed to a function in a 3254library of a different code unit width, for example, a pattern compiled by 3255the 8-bit library is passed to a 16-bit or 32-bit library function. 3256<pre> 3257 PCRE2_ERROR_BADOFFSET 3258</pre> 3259The value of <i>startoffset</i> was greater than the length of the subject. 3260<pre> 3261 PCRE2_ERROR_BADOPTION 3262</pre> 3263An unrecognized bit was set in the <i>options</i> argument. 3264<pre> 3265 PCRE2_ERROR_BADUTFOFFSET 3266</pre> 3267The UTF code unit sequence that was passed as a subject was checked and found 3268to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of 3269<i>startoffset</i> did not point to the beginning of a UTF character or the end 3270of the subject. 3271<pre> 3272 PCRE2_ERROR_CALLOUT 3273</pre> 3274This error is never generated by <b>pcre2_match()</b> itself. It is provided for 3275use by callout functions that want to cause <b>pcre2_match()</b> or 3276<b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the 3277<a href="pcre2callout.html"><b>pcre2callout</b></a> 3278documentation for details. 3279<pre> 3280 PCRE2_ERROR_DEPTHLIMIT 3281</pre> 3282The nested backtracking depth limit was reached. 3283<pre> 3284 PCRE2_ERROR_HEAPLIMIT 3285</pre> 3286The heap limit was reached. 3287<pre> 3288 PCRE2_ERROR_INTERNAL 3289</pre> 3290An unexpected internal error has occurred. This error could be caused by a bug 3291in PCRE2 or by overwriting of the compiled pattern. 3292<pre> 3293 PCRE2_ERROR_JIT_STACKLIMIT 3294</pre> 3295This error is returned when a pattern that was successfully studied using JIT 3296is being matched, but the memory available for the just-in-time processing 3297stack is not large enough. See the 3298<a href="pcre2jit.html"><b>pcre2jit</b></a> 3299documentation for more details. 3300<pre> 3301 PCRE2_ERROR_MATCHLIMIT 3302</pre> 3303The backtracking match limit was reached. 3304<pre> 3305 PCRE2_ERROR_NOMEMORY 3306</pre> 3307Heap memory is used to remember backtracking points. This error is given when 3308the memory allocation function (default or custom) fails. Note that a different 3309error, PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds 3310the heap limit. PCRE2_ERROR_NOMEMORY is also returned if 3311PCRE2_COPY_MATCHED_SUBJECT is set and memory allocation fails. 3312<pre> 3313 PCRE2_ERROR_NULL 3314</pre> 3315Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed 3316as NULL. 3317<pre> 3318 PCRE2_ERROR_RECURSELOOP 3319</pre> 3320This error is returned when <b>pcre2_match()</b> detects a recursion loop within 3321the pattern. Specifically, it means that either the whole pattern or a 3322capture group has been called recursively for the second time at the same 3323position in the subject string. Some simple patterns that might do this are 3324detected and faulted at compile time, but more complicated cases, in particular 3325mutual recursions between two different groups, cannot be detected until 3326matching is attempted. 3327<a name="geterrormessage"></a></P> 3328<br><a name="SEC33" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br> 3329<P> 3330<b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3331<b> PCRE2_SIZE <i>bufflen</i>);</b> 3332</P> 3333<P> 3334A text message for an error code from any PCRE2 function (compile, match, or 3335auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code 3336is passed as the first argument, with the remaining two arguments specifying a 3337code unit buffer and its length in code units, into which the text message is 3338placed. The message is returned in code units of the appropriate width for the 3339library that is being used. 3340</P> 3341<P> 3342The returned message is terminated with a trailing zero, and the function 3343returns the number of code units used, excluding the trailing zero. If the 3344error number is unknown, the negative error code PCRE2_ERROR_BADDATA is 3345returned. If the buffer is too small, the message is truncated (but still with 3346a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. 3347None of the messages are very long; a buffer size of 120 code units is ample. 3348<a name="extractbynumber"></a></P> 3349<br><a name="SEC34" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> 3350<P> 3351<b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3352<b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 3353<br> 3354<br> 3355<b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3356<b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 3357<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3358<br> 3359<br> 3360<b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 3361<b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 3362<b> PCRE2_SIZE *<i>bufflen</i>);</b> 3363<br> 3364<br> 3365<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3366</P> 3367<P> 3368Captured substrings can be accessed directly by using the ovector as described 3369<a href="#matchedstrings">above.</a> 3370For convenience, auxiliary functions are provided for extracting captured 3371substrings as new, separate, zero-terminated strings. A substring that contains 3372a binary zero is correctly extracted and has a further zero added on the end, 3373but the result is not, of course, a C string. 3374</P> 3375<P> 3376The functions in this section identify substrings by number. The number zero 3377refers to the entire matched substring, with higher numbers referring to 3378substrings captured by parenthesized groups. After a partial match, only 3379substring zero is available. An attempt to extract any other substring gives 3380the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for 3381extracting captured substrings by name. 3382</P> 3383<P> 3384If a pattern uses the \K escape sequence within a positive assertion, the 3385reported start of a successful match can be greater than the end of the match. 3386For example, if the pattern (?=ab\K) is matched against "ab", the start and 3387end offset values for the match are 2 and 0. In this situation, calling these 3388functions with a zero substring number extracts a zero-length empty string. 3389</P> 3390<P> 3391You can find the length in code units of a captured substring without 3392extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first 3393argument is a pointer to the match data block, the second is the group number, 3394and the third is a pointer to a variable into which the length is placed. If 3395you just want to know whether or not the substring has been captured, you can 3396pass the third argument as NULL. 3397</P> 3398<P> 3399The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring 3400into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it 3401into new memory, obtained using the same memory allocation function that was 3402used for the match data block. The first two arguments of these functions are a 3403pointer to the match data block and a capture group number. 3404</P> 3405<P> 3406The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to 3407the buffer and a pointer to a variable that contains its length in code units. 3408This is updated to contain the actual number of code units used for the 3409extracted substring, excluding the terminating zero. 3410</P> 3411<P> 3412For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point 3413to variables that are updated with a pointer to the new memory and the number 3414of code units that comprise the substring, again excluding the terminating 3415zero. When the substring is no longer needed, the memory should be freed by 3416calling <b>pcre2_substring_free()</b>. 3417</P> 3418<P> 3419The return value from all these functions is zero for success, or a negative 3420error code. If the pattern match failed, the match failure code is returned. 3421If a substring number greater than zero is used after a partial match, 3422PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: 3423<pre> 3424 PCRE2_ERROR_NOMEMORY 3425</pre> 3426The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the 3427attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>. 3428<pre> 3429 PCRE2_ERROR_NOSUBSTRING 3430</pre> 3431There is no substring with that number in the pattern, that is, the number is 3432greater than the number of capturing parentheses. 3433<pre> 3434 PCRE2_ERROR_UNAVAILABLE 3435</pre> 3436The substring number, though not greater than the number of captures in the 3437pattern, is greater than the number of slots in the ovector, so the substring 3438could not be captured. 3439<pre> 3440 PCRE2_ERROR_UNSET 3441</pre> 3442The substring did not participate in the match. For example, if the pattern is 3443(abc)|(def) and the subject is "def", and the ovector contains at least two 3444capturing slots, substring number 1 is unset. 3445</P> 3446<br><a name="SEC35" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br> 3447<P> 3448<b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 3449<b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 3450<br> 3451<br> 3452<b>void pcre2_substring_list_free(PCRE2_UCHAR **<i>list</i>);</b> 3453</P> 3454<P> 3455The <b>pcre2_substring_list_get()</b> function extracts all available substrings 3456and builds a list of pointers to them. It also (optionally) builds a second 3457list that contains their lengths (in code units), excluding a terminating zero 3458that is added to each of them. All this is done in a single block of memory 3459that is obtained using the same memory allocation function that was used to get 3460the match data block. 3461</P> 3462<P> 3463This function must be called only after a successful match. If called after a 3464partial match, the error code PCRE2_ERROR_PARTIAL is returned. 3465</P> 3466<P> 3467The address of the memory block is returned via <i>listptr</i>, which is also 3468the start of the list of string pointers. The end of the list is marked by a 3469NULL pointer. The address of the list of lengths is returned via 3470<i>lengthsptr</i>. If your strings do not contain binary zeros and you do not 3471therefore need the lengths, you may supply NULL as the <b>lengthsptr</b> 3472argument to disable the creation of a list of lengths. The yield of the 3473function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block 3474could not be obtained. When the list is no longer needed, it should be freed by 3475calling <b>pcre2_substring_list_free()</b>. 3476</P> 3477<P> 3478If this function encounters a substring that is unset, which can happen when 3479capture group number <i>n+1</i> matches some part of the subject, but group 3480<i>n</i> has not been used at all, it returns an empty string. This can be 3481distinguished from a genuine zero-length substring by inspecting the 3482appropriate offset in the ovector, which contain PCRE2_UNSET for unset 3483substrings, or by calling <b>pcre2_substring_length_bynumber()</b>. 3484<a name="extractbyname"></a></P> 3485<br><a name="SEC36" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> 3486<P> 3487<b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 3488<b> PCRE2_SPTR <i>name</i>);</b> 3489<br> 3490<br> 3491<b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 3492<b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 3493<br> 3494<br> 3495<b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 3496<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3497<br> 3498<br> 3499<b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 3500<b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3501<br> 3502<br> 3503<b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3504</P> 3505<P> 3506To extract a substring by name, you first have to find associated number. 3507For example, for this pattern: 3508<pre> 3509 (a+)b(?<xxx>\d+)... 3510</pre> 3511the number of the capture group called "xxx" is 2. If the name is known to be 3512unique (PCRE2_DUPNAMES was not set), you can find the number from the name by 3513calling <b>pcre2_substring_number_from_name()</b>. The first argument is the 3514compiled pattern, and the second is the name. The yield of the function is the 3515group number, PCRE2_ERROR_NOSUBSTRING if there is no group with that name, or 3516PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one group with that name. 3517Given the number, you can extract the substring directly from the ovector, or 3518use one of the "bynumber" functions described above. 3519</P> 3520<P> 3521For convenience, there are also "byname" functions that correspond to the 3522"bynumber" functions, the only difference being that the second argument is a 3523name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate 3524names, these functions scan all the groups with the given name, and return the 3525captured substring from the first named group that is set. 3526</P> 3527<P> 3528If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is 3529returned. If all groups with the name have numbers that are greater than the 3530number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there 3531is at least one group with a slot in the ovector, but no group is found to be 3532set, PCRE2_ERROR_UNSET is returned. 3533</P> 3534<P> 3535<b>Warning:</b> If the pattern uses the (?| feature to set up multiple 3536capture groups with the same number, as described in the 3537<a href="pcre2pattern.html#dupgroupnumber">section on duplicate group numbers</a> 3538in the 3539<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3540page, you cannot use names to distinguish the different capture groups, because 3541names are not included in the compiled code. The matching process uses only 3542numbers. For this reason, the use of different names for groups with the 3543same number causes an error at compile time. 3544<a name="substitutions"></a></P> 3545<br><a name="SEC37" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br> 3546<P> 3547<b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3548<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3549<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3550<b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b> 3551<b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 3552<b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 3553</P> 3554<P> 3555This function optionally calls <b>pcre2_match()</b> and then makes a copy of the 3556subject string in <i>outputbuffer</i>, replacing parts that were matched with 3557the <i>replacement</i> string, whose length is supplied in <b>rlength</b>, which 3558can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. As a 3559special case, if <i>replacement</i> is NULL and <i>rlength</i> is zero, the 3560replacement is assumed to be an empty string. If <i>rlength</i> is non-zero, an 3561error occurs if <i>replacement</i> is NULL. 3562</P> 3563<P> 3564There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to return just 3565the replacement string(s). The default action is to perform just one 3566replacement if the pattern matches, but there is an option that requests 3567multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below). 3568</P> 3569<P> 3570If successful, <b>pcre2_substitute()</b> returns the number of substitutions 3571that were carried out. This may be zero if no match was found, and is never 3572greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A negative value is 3573returned if an error is detected. 3574</P> 3575<P> 3576Matches in which a \K item in a lookahead in the pattern causes the match to 3577end before it starts are not supported, and give rise to an error return. For 3578global replacements, matches in which \K in a lookbehind causes the match to 3579start earlier than the point that was reached in the previous iteration are 3580also not supported. 3581</P> 3582<P> 3583The first seven arguments of <b>pcre2_substitute()</b> are the same as for 3584<b>pcre2_match()</b>, except that the partial matching options are not 3585permitted, and <i>match_data</i> may be passed as NULL, in which case a match 3586data block is obtained and freed within this function, using memory management 3587functions from the match context, if provided, or else those that were used to 3588allocate memory for the compiled code. 3589</P> 3590<P> 3591If <i>match_data</i> is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the 3592provided block is used for all calls to <b>pcre2_match()</b>, and its contents 3593afterwards are the result of the final call. For global changes, this will 3594always be a no-match error. The contents of the ovector within the match data 3595block may or may not have been changed. 3596</P> 3597<P> 3598As well as the usual options for <b>pcre2_match()</b>, a number of additional 3599options can be set in the <i>options</i> argument of <b>pcre2_substitute()</b>. 3600One such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external 3601<i>match_data</i> block must be provided, and it must have already been used for 3602an external call to <b>pcre2_match()</b> with the same pattern and subject 3603arguments. The data in the <i>match_data</i> block (return code, offset vector) 3604is then used for the first substitution instead of calling <b>pcre2_match()</b> 3605from within <b>pcre2_substitute()</b>. This allows an application to check for a 3606match before choosing to substitute, without having to repeat the match. 3607</P> 3608<P> 3609The contents of the externally supplied match data block are not changed when 3610PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTITUTE_GLOBAL is also set, 3611<b>pcre2_match()</b> is called after the first substitution to check for further 3612matches, but this is done using an internally obtained match data block, thus 3613always leaving the external block unchanged. 3614</P> 3615<P> 3616The <i>code</i> argument is not used for matching before the first substitution 3617when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided, even when 3618PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains information such as the 3619UTF setting and the number of capturing parentheses in the pattern. 3620</P> 3621<P> 3622The default action of <b>pcre2_substitute()</b> is to return a copy of the 3623subject string with matched substrings replaced. However, if 3624PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are 3625returned. In the global case, multiple replacements are concatenated in the 3626output buffer. Substitution callouts (see 3627<a href="#subcallouts">below)</a> 3628can be used to separate them if necessary. 3629</P> 3630<P> 3631The <i>outlengthptr</i> argument of <b>pcre2_substitute()</b> must point to a 3632variable that contains the length, in code units, of the output buffer. If the 3633function is successful, the value is updated to contain the length in code 3634units of the new string, excluding the trailing zero that is automatically 3635added. 3636</P> 3637<P> 3638If the function is not successful, the value set via <i>outlengthptr</i> depends 3639on the type of error. For syntax errors in the replacement string, the value is 3640the offset in the replacement string where the error was detected. For other 3641errors, the value is PCRE2_UNSET by default. This includes the case of the 3642output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set. 3643</P> 3644<P> 3645PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is 3646too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If 3647this option is set, however, <b>pcre2_substitute()</b> continues to go through 3648the motions of matching and substituting (without, of course, writing anything) 3649in order to compute the size of buffer that is needed. This value is passed 3650back via the <i>outlengthptr</i> variable, with the result of the function still 3651being PCRE2_ERROR_NOMEMORY. 3652</P> 3653<P> 3654Passing a buffer size of zero is a permitted way of finding out how much memory 3655is needed for given substitution. However, this does mean that the entire 3656operation is carried out twice. Depending on the application, it may be more 3657efficient to allocate a large buffer and free the excess afterwards, instead of 3658using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH. 3659</P> 3660<P> 3661The replacement string, which is interpreted as a UTF string in UTF mode, is 3662checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An invalid UTF 3663replacement string causes an immediate return with the relevant UTF error code. 3664</P> 3665<P> 3666If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not interpreted 3667in any way. By default, however, a dollar character is an escape character that 3668can specify the insertion of characters from capture groups and names from 3669(*MARK) or other control verbs in the pattern. Dollar is the only escape 3670character (backslash is treated as literal). The following forms are always 3671recognized: 3672<pre> 3673 $$ insert a dollar character 3674 $<n> or ${<n>} insert the contents of group <n> 3675 $*MARK or ${*MARK} insert a control verb name 3676</pre> 3677Either a group number or a group name can be given for <n>. Curly brackets are 3678required only if the following character would be interpreted as part of the 3679number or name. The number may be zero to include the entire matched string. 3680For example, if the pattern a(b)c is matched with "=abc=" and the replacement 3681string "+$1$0$1+", the result is "=+babcb+=". 3682</P> 3683<P> 3684$*MARK inserts the name from the last encountered backtracking control verb on 3685the matching path that has a name. (*MARK) must always include a name, but the 3686other verbs need not. For example, in the case of (*MARK:A)(*PRUNE) the name 3687inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". This 3688facility can be used to perform simple simultaneous substitutions, as this 3689<b>pcre2test</b> example shows: 3690<pre> 3691 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} 3692 apple lemon 3693 2: pear orange 3694</pre> 3695PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, 3696replacing every matching substring. If this option is not set, only the first 3697matching substring is replaced. The search for matches takes place in the 3698original subject string (that is, previous replacements do not affect it). 3699Iteration is implemented by advancing the <i>startoffset</i> value for each 3700search, which is always passed the entire subject string. If an offset limit is 3701set in the match context, searching stops when that limit is reached. 3702</P> 3703<P> 3704You can restrict the effect of a global substitution to a portion of the 3705subject string by setting either or both of <i>startoffset</i> and an offset 3706limit. Here is a <b>pcre2test</b> example: 3707<pre> 3708 /B/g,replace=!,use_offset_limit 3709 ABC ABC ABC ABC\=offset=3,offset_limit=12 3710 2: ABC A!C A!C ABC 3711</pre> 3712When continuing with global substitutions after matching a substring with zero 3713length, an attempt to find a non-empty match at the same offset is performed. 3714If this is not successful, the offset is advanced by one character except when 3715CRLF is a valid newline sequence and the next two characters are CR, LF. In 3716this case, the offset is advanced by two characters. 3717</P> 3718<P> 3719PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do 3720not appear in the pattern to be treated as unset groups. This option should be 3721used with care, because it means that a typo in a group name or number no 3722longer causes the PCRE2_ERROR_NOSUBSTRING error. 3723</P> 3724<P> 3725PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including unknown 3726groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty 3727strings when inserted as described above. If this option is not set, an attempt 3728to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does 3729not influence the extended substitution syntax described below. 3730</P> 3731<P> 3732PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the 3733replacement string. Without this option, only the dollar character is special, 3734and only the group insertion forms listed above are valid. When 3735PCRE2_SUBSTITUTE_EXTENDED is set, two things change: 3736</P> 3737<P> 3738Firstly, backslash in a replacement string is interpreted as an escape 3739character. The usual forms such as \n or \x{ddd} can be used to specify 3740particular character codes, and backslash followed by any non-alphanumeric 3741character quotes that character. Extended quoting can be coded using \Q...\E, 3742exactly as in pattern strings. 3743</P> 3744<P> 3745There are also four escape sequences for forcing the case of inserted letters. 3746The insertion mechanism has three states: no case forcing, force upper case, 3747and force lower case. The escape sequences change the current state: \U and 3748\L change to upper or lower case forcing, respectively, and \E (when not 3749terminating a \Q quoted sequence) reverts to no case forcing. The sequences 3750\u and \l force the next character (if it is a letter) to upper or lower 3751case, respectively, and then the state automatically reverts to no case 3752forcing. Case forcing applies to all inserted characters, including those from 3753capture groups and letters within \Q...\E quoted sequences. If either 3754PCRE2_UTF or PCRE2_UCP was set when the pattern was compiled, Unicode 3755properties are used for case forcing characters whose code points are greater 3756than 127. 3757</P> 3758<P> 3759Note that case forcing sequences such as \U...\E do not nest. For example, 3760the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no 3761effect. Note also that the PCRE2_ALT_BSUX and PCRE2_EXTRA_ALT_BSUX options do 3762not apply to replacement strings. 3763</P> 3764<P> 3765The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more 3766flexibility to capture group substitution. The syntax is similar to that used 3767by Bash: 3768<pre> 3769 ${<n>:-<string>} 3770 ${<n>:+<string1>:<string2>} 3771</pre> 3772As before, <n> may be a group number or a name. The first form specifies a 3773default value. If group <n> is set, its value is inserted; if not, <string> is 3774expanded and the result inserted. The second form specifies strings that are 3775expanded and inserted when group <n> is set or unset, respectively. The first 3776form is just a convenient shorthand for 3777<pre> 3778 ${<n>:+${<n>}:<string>} 3779</pre> 3780Backslash can be used to escape colons and closing curly brackets in the 3781replacement strings. A change of the case forcing state within a replacement 3782string remains in force afterwards, as shown in this <b>pcre2test</b> example: 3783<pre> 3784 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo 3785 body 3786 1: hello 3787 somebody 3788 1: HELLO 3789</pre> 3790The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended 3791substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown 3792groups in the extended syntax forms to be treated as unset. 3793</P> 3794<P> 3795If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_UNKNOWN_UNSET, 3796PCRE2_SUBSTITUTE_UNSET_EMPTY, and PCRE2_SUBSTITUTE_EXTENDED are irrelevant and 3797are ignored. 3798</P> 3799<br><b> 3800Substitution errors 3801</b><br> 3802<P> 3803In the event of an error, <b>pcre2_substitute()</b> returns a negative error 3804code. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors from 3805<b>pcre2_match()</b> are passed straight back. 3806</P> 3807<P> 3808PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion, 3809unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. 3810</P> 3811<P> 3812PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an 3813unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple 3814(non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set. 3815</P> 3816<P> 3817PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the 3818PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is 3819needed is returned via <i>outlengthptr</i>. Note that this does not happen by 3820default. 3821</P> 3822<P> 3823PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the 3824<i>match_data</i> argument is NULL or if the <i>subject</i> or <i>replacement</i> 3825arguments are NULL. For backward compatibility reasons an exception is made for 3826the <i>replacement</i> argument if the <i>rlength</i> argument is also 0. 3827</P> 3828<P> 3829PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the 3830replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE 3831(invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE (closing curly bracket 3832not found), PCRE2_ERROR_BADSUBSTITUTION (syntax error in extended group 3833substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before 3834it started or the match started earlier than the current position in the 3835subject, which can happen if \K is used in an assertion). 3836</P> 3837<P> 3838As for all PCRE2 errors, a text message that describes the error can be 3839obtained by calling the <b>pcre2_get_error_message()</b> function (see 3840"Obtaining a textual error message" 3841<a href="#geterrormessage">above).</a> 3842<a name="subcallouts"></a></P> 3843<br><b> 3844Substitution callouts 3845</b><br> 3846<P> 3847<b>int pcre2_set_substitute_callout(pcre2_match_context *<i>mcontext</i>,</b> 3848<b> int (*<i>callout_function</i>)(pcre2_substitute_callout_block *, void *),</b> 3849<b> void *<i>callout_data</i>);</b> 3850<br> 3851<br> 3852The <b>pcre2_set_substitution_callout()</b> function can be used to specify a 3853callout function for <b>pcre2_substitute()</b>. This information is passed in 3854a match context. The callout function is called after each substitution has 3855been processed, but it can cause the replacement not to happen. The callout 3856function is not called for simulated substitutions that happen as a result of 3857the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. 3858</P> 3859<P> 3860The first argument of the callout function is a pointer to a substitute callout 3861block structure, which contains the following fields, not necessarily in this 3862order: 3863<pre> 3864 uint32_t <i>version</i>; 3865 uint32_t <i>subscount</i>; 3866 PCRE2_SPTR <i>input</i>; 3867 PCRE2_SPTR <i>output</i>; 3868 PCRE2_SIZE <i>*ovector</i>; 3869 uint32_t <i>oveccount</i>; 3870 PCRE2_SIZE <i>output_offsets[2]</i>; 3871</pre> 3872The <i>version</i> field contains the version number of the block format. The 3873current version is 0. The version number will increase in future if more fields 3874are added, but the intention is never to remove any of the existing fields. 3875</P> 3876<P> 3877The <i>subscount</i> field is the number of the current match. It is 1 for the 3878first callout, 2 for the second, and so on. The <i>input</i> and <i>output</i> 3879pointers are copies of the values passed to <b>pcre2_substitute()</b>. 3880</P> 3881<P> 3882The <i>ovector</i> field points to the ovector, which contains the result of the 3883most recent match. The <i>oveccount</i> field contains the number of pairs that 3884are set in the ovector, and is always greater than zero. 3885</P> 3886<P> 3887The <i>output_offsets</i> vector contains the offsets of the replacement in the 3888output string. This has already been processed for dollar and (if requested) 3889backslash substitutions as described above. 3890</P> 3891<P> 3892The second argument of the callout function is the value passed as 3893<i>callout_data</i> when the function was registered. The value returned by the 3894callout function is interpreted as follows: 3895</P> 3896<P> 3897If the value is zero, the replacement is accepted, and, if 3898PCRE2_SUBSTITUTE_GLOBAL is set, processing continues with a search for the next 3899match. If the value is not zero, the current replacement is not accepted. If 3900the value is greater than zero, processing continues when 3901PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than zero or 3902PCRE2_SUBSTITUTE_GLOBAL is not set), the rest of the input is copied to the 3903output and the call to <b>pcre2_substitute()</b> exits, returning the number of 3904matches so far. 3905</P> 3906<br><a name="SEC38" href="#TOC1">DUPLICATE CAPTURE GROUP NAMES</a><br> 3907<P> 3908<b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 3909<b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 3910</P> 3911<P> 3912When a pattern is compiled with the PCRE2_DUPNAMES option, names for capture 3913groups are not required to be unique. Duplicate names are always allowed for 3914groups with the same number, created by using the (?| feature. Indeed, if such 3915groups are named, they are required to use the same names. 3916</P> 3917<P> 3918Normally, patterns that use duplicate names are such that in any one match, 3919only one of each set of identically-named groups participates. An example is 3920shown in the 3921<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3922documentation. 3923</P> 3924<P> 3925When duplicates are present, <b>pcre2_substring_copy_byname()</b> and 3926<b>pcre2_substring_get_byname()</b> return the first substring corresponding to 3927the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is 3928returned. The <b>pcre2_substring_number_from_name()</b> function returns the 3929error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. 3930</P> 3931<P> 3932If you want to get full details of all captured substrings for a given name, 3933you must use the <b>pcre2_substring_nametable_scan()</b> function. The first 3934argument is the compiled pattern, and the second is the name. If the third and 3935fourth arguments are NULL, the function returns a group number for a unique 3936name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. 3937</P> 3938<P> 3939When the third and fourth arguments are not NULL, they must be pointers to 3940variables that are updated by the function. After it has run, they point to the 3941first and last entries in the name-to-number table for the given name, and the 3942function returns the length of each entry in code units. In both cases, 3943PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. 3944</P> 3945<P> 3946The format of the name table is described 3947<a href="#infoaboutpattern">above</a> 3948in the section entitled <i>Information about a pattern</i>. Given all the 3949relevant entries for the name, you can extract each of their numbers, and hence 3950the captured data. 3951</P> 3952<br><a name="SEC39" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br> 3953<P> 3954The traditional matching function uses a similar algorithm to Perl, which stops 3955when it finds the first match at a given point in the subject. If you want to 3956find all possible matches, or the longest possible match at a given position, 3957consider using the alternative matching function (see below) instead. If you 3958cannot use the alternative function, you can kludge it up by making use of the 3959callout facility, which is described in the 3960<a href="pcre2callout.html"><b>pcre2callout</b></a> 3961documentation. 3962</P> 3963<P> 3964What you have to do is to insert a callout right at the end of the pattern. 3965When your callout function is called, extract and save the current matched 3966substring. Then return 1, which forces <b>pcre2_match()</b> to backtrack and try 3967other alternatives. Ultimately, when it runs out of matches, 3968<b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH. 3969<a name="dfamatch"></a></P> 3970<br><a name="SEC40" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> 3971<P> 3972<b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3973<b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3974<b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3975<b> pcre2_match_context *<i>mcontext</i>,</b> 3976<b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 3977</P> 3978<P> 3979The function <b>pcre2_dfa_match()</b> is called to match a subject string 3980against a compiled pattern, using a matching algorithm that scans the subject 3981string just once (not counting lookaround assertions), and does not backtrack 3982(except when processing lookaround assertions). This has different 3983characteristics to the normal algorithm, and is not compatible with Perl. Some 3984of the features of PCRE2 patterns are not supported. Nevertheless, there are 3985times when this kind of matching can be useful. For a discussion of the two 3986matching algorithms, and a list of features that <b>pcre2_dfa_match()</b> does 3987not support, see the 3988<a href="pcre2matching.html"><b>pcre2matching</b></a> 3989documentation. 3990</P> 3991<P> 3992The arguments for the <b>pcre2_dfa_match()</b> function are the same as for 3993<b>pcre2_match()</b>, plus two extras. The ovector within the match data block 3994is used in a different way, and this is described below. The other common 3995arguments are used in the same way as for <b>pcre2_match()</b>, so their 3996description is not repeated here. 3997</P> 3998<P> 3999The two additional arguments provide workspace for the function. The workspace 4000vector should contain at least 20 elements. It is used for keeping track of 4001multiple paths through the pattern tree. More workspace is needed for patterns 4002and subjects where there are a lot of potential matches. 4003</P> 4004<P> 4005Here is an example of a simple call to <b>pcre2_dfa_match()</b>: 4006<pre> 4007 int wspace[20]; 4008 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 4009 int rc = pcre2_dfa_match( 4010 re, /* result of pcre2_compile() */ 4011 "some string", /* the subject string */ 4012 11, /* the length of the subject string */ 4013 0, /* start at offset 0 in the subject */ 4014 0, /* default options */ 4015 md, /* the match data block */ 4016 NULL, /* a match context; NULL means use defaults */ 4017 wspace, /* working space vector */ 4018 20); /* number of elements (NOT size in bytes) */ 4019</PRE> 4020</P> 4021<br><b> 4022Option bits for <b>pcre2_dfa_match()</b> 4023</b><br> 4024<P> 4025The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must 4026be zero. The only bits that may be set are PCRE2_ANCHORED, 4027PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, 4028PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, 4029PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but the last 4030four of these are exactly the same as for <b>pcre2_match()</b>, so their 4031description is not repeated here. 4032<pre> 4033 PCRE2_PARTIAL_HARD 4034 PCRE2_PARTIAL_SOFT 4035</pre> 4036These have the same general effect as they do for <b>pcre2_match()</b>, but the 4037details are slightly different. When PCRE2_PARTIAL_HARD is set for 4038<b>pcre2_dfa_match()</b>, it returns PCRE2_ERROR_PARTIAL if the end of the 4039subject is reached and there is still at least one matching possibility that 4040requires additional characters. This happens even if some complete matches have 4041already been found. When PCRE2_PARTIAL_SOFT is set, the return code 4042PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the 4043subject is reached, there have been no complete matches, but there is still at 4044least one matching possibility. The portion of the string that was inspected 4045when the longest partial match was found is set as the first matching string in 4046both cases. There is a more detailed discussion of partial and multi-segment 4047matching, with examples, in the 4048<a href="pcre2partial.html"><b>pcre2partial</b></a> 4049documentation. 4050<pre> 4051 PCRE2_DFA_SHORTEST 4052</pre> 4053Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as 4054soon as it has found one match. Because of the way the alternative algorithm 4055works, this is necessarily the shortest possible match at the first possible 4056matching point in the subject string. 4057<pre> 4058 PCRE2_DFA_RESTART 4059</pre> 4060When <b>pcre2_dfa_match()</b> returns a partial match, it is possible to call it 4061again, with additional subject characters, and have it continue with the same 4062match. The PCRE2_DFA_RESTART option requests this action; when it is set, the 4063<i>workspace</i> and <i>wscount</i> options must reference the same vector as 4064before because data about the match so far is left in them after a partial 4065match. There is more discussion of this facility in the 4066<a href="pcre2partial.html"><b>pcre2partial</b></a> 4067documentation. 4068</P> 4069<br><b> 4070Successful returns from <b>pcre2_dfa_match()</b> 4071</b><br> 4072<P> 4073When <b>pcre2_dfa_match()</b> succeeds, it may have matched more than one 4074substring in the subject. Note, however, that all the matches from one run of 4075the function start at the same point in the subject. The shorter matches are 4076all initial substrings of the longer matches. For example, if the pattern 4077<pre> 4078 <.*> 4079</pre> 4080is matched against the string 4081<pre> 4082 This is <something> <something else> <something further> no more 4083</pre> 4084the three matched strings are 4085<pre> 4086 <something> <something else> <something further> 4087 <something> <something else> 4088 <something> 4089</pre> 4090On success, the yield of the function is a number greater than zero, which is 4091the number of matched substrings. The offsets of the substrings are returned in 4092the ovector, and can be extracted by number in the same way as for 4093<b>pcre2_match()</b>, but the numbers bear no relation to any capture groups 4094that may exist in the pattern, because DFA matching does not support capturing. 4095</P> 4096<P> 4097Calls to the convenience functions that extract substrings by name 4098return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a 4099DFA match. The convenience functions that extract substrings by number never 4100return PCRE2_ERROR_NOSUBSTRING. 4101</P> 4102<P> 4103The matched strings are stored in the ovector in reverse order of length; that 4104is, the longest matching string is first. If there were too many matches to fit 4105into the ovector, the yield of the function is zero, and the vector is filled 4106with the longest matches. 4107</P> 4108<P> 4109NOTE: PCRE2's "auto-possessification" optimization usually applies to character 4110repeats at the end of a pattern (as well as internally). For example, the 4111pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this 4112means that only one possible match is found. If you really do want multiple 4113matches in such cases, either use an ungreedy repeat such as "a\d+?" or set 4114the PCRE2_NO_AUTO_POSSESS option when compiling. 4115</P> 4116<br><b> 4117Error returns from <b>pcre2_dfa_match()</b> 4118</b><br> 4119<P> 4120The <b>pcre2_dfa_match()</b> function returns a negative number when it fails. 4121Many of the errors are the same as for <b>pcre2_match()</b>, as described 4122<a href="#errorlist">above.</a> 4123There are in addition the following errors that are specific to 4124<b>pcre2_dfa_match()</b>: 4125<pre> 4126 PCRE2_ERROR_DFA_UITEM 4127</pre> 4128This return is given if <b>pcre2_dfa_match()</b> encounters an item in the 4129pattern that it does not support, for instance, the use of \C in a UTF mode or 4130a backreference. 4131<pre> 4132 PCRE2_ERROR_DFA_UCOND 4133</pre> 4134This return is given if <b>pcre2_dfa_match()</b> encounters a condition item 4135that uses a backreference for the condition, or a test for recursion in a 4136specific capture group. These are not supported. 4137<pre> 4138 PCRE2_ERROR_DFA_UINVALID_UTF 4139</pre> 4140This return is given if <b>pcre2_dfa_match()</b> is called for a pattern that 4141was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for DFA 4142matching. 4143<pre> 4144 PCRE2_ERROR_DFA_WSSIZE 4145</pre> 4146This return is given if <b>pcre2_dfa_match()</b> runs out of space in the 4147<i>workspace</i> vector. 4148<pre> 4149 PCRE2_ERROR_DFA_RECURSE 4150</pre> 4151When a recursion or subroutine call is processed, the matching function calls 4152itself recursively, using private memory for the ovector and <i>workspace</i>. 4153This error is given if the internal ovector is not large enough. This should be 4154extremely rare, as a vector of size 1000 is used. 4155<pre> 4156 PCRE2_ERROR_DFA_BADRESTART 4157</pre> 4158When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_DFA_RESTART</b> option, 4159some plausibility checks are made on the contents of the workspace, which 4160should contain data about the previous partial match. If any of these checks 4161fail, this error is given. 4162</P> 4163<br><a name="SEC41" href="#TOC1">SEE ALSO</a><br> 4164<P> 4165<b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>, 4166<b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3), 4167<b>pcre2sample</b>(3), <b>pcre2unicode</b>(3). 4168</P> 4169<br><a name="SEC42" href="#TOC1">AUTHOR</a><br> 4170<P> 4171Philip Hazel 4172<br> 4173Retired from University Computing Service 4174<br> 4175Cambridge, England. 4176<br> 4177</P> 4178<br><a name="SEC43" href="#TOC1">REVISION</a><br> 4179<P> 4180Last updated: 24 April 2024 4181<br> 4182Copyright © 1997-2024 University of Cambridge. 4183<br> 4184<p> 4185Return to the <a href="index.html">PCRE2 index page</a>. 4186</p> 4187