1 /*
2 * Copyright © 2007,2008,2009,2010 Red Hat, Inc.
3 * Copyright © 2012,2018 Google, Inc.
4 *
5 * This is part of HarfBuzz, a text shaping library.
6 *
7 * Permission is hereby granted, without written agreement and without
8 * license or royalty fees, to use, copy, modify, and distribute this
9 * software and its documentation for any purpose, provided that the
10 * above copyright notice and the following two paragraphs appear in
11 * all copies of this software.
12 *
13 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
14 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
15 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
16 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
17 * DAMAGE.
18 *
19 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
20 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
21 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
22 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
23 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
24 *
25 * Red Hat Author(s): Behdad Esfahbod
26 * Google Author(s): Behdad Esfahbod
27 */
28
29 #ifndef HB_MACHINERY_HH
30 #define HB_MACHINERY_HH
31
32 #include "hb.hh"
33 #include "hb-blob.hh"
34
35 #include "hb-dispatch.hh"
36 #include "hb-sanitize.hh"
37
38
39 /*
40 * Casts
41 */
42
43 /* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
44 * location pointed to by P plus Ofs bytes. */
45 template<typename Type>
StructAtOffset(const void * P,unsigned int offset)46 static inline const Type& StructAtOffset(const void *P, unsigned int offset)
47 { return * reinterpret_cast<const Type*> ((const char *) P + offset); }
48 template<typename Type>
StructAtOffset(void * P,unsigned int offset)49 static inline Type& StructAtOffset(void *P, unsigned int offset)
50 { return * reinterpret_cast<Type*> ((char *) P + offset); }
51 template<typename Type>
StructAtOffsetUnaligned(const void * P,unsigned int offset)52 static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
53 {
54 #pragma GCC diagnostic push
55 #pragma GCC diagnostic ignored "-Wcast-align"
56 return * reinterpret_cast<const Type*> ((const char *) P + offset);
57 #pragma GCC diagnostic pop
58 }
59 template<typename Type>
StructAtOffsetUnaligned(void * P,unsigned int offset)60 static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
61 {
62 #pragma GCC diagnostic push
63 #pragma GCC diagnostic ignored "-Wcast-align"
64 return * reinterpret_cast<Type*> ((char *) P + offset);
65 #pragma GCC diagnostic pop
66 }
67
68 /* StructAfter<T>(X) returns the struct T& that is placed after X.
69 * Works with X of variable size also. X must implement get_size() */
70 template<typename Type, typename TObject>
StructAfter(const TObject & X)71 static inline const Type& StructAfter(const TObject &X)
72 { return StructAtOffset<Type>(&X, X.get_size()); }
73 template<typename Type, typename TObject>
StructAfter(TObject & X)74 static inline Type& StructAfter(TObject &X)
75 { return StructAtOffset<Type>(&X, X.get_size()); }
76
77
78 /*
79 * Size checking
80 */
81
82 /* Size signifying variable-sized array */
83 #ifndef HB_VAR_ARRAY
84 #define HB_VAR_ARRAY 1
85 #endif
86
87 /* Check _assertion in a method environment */
88 #define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
89 void _instance_assertion_on_line_##_line () const \
90 { static_assert ((_assertion), ""); }
91 # define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
92 # define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
93
94 /* Check that _code compiles in a method environment */
95 #define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
96 void _compiles_assertion_on_line_##_line () const \
97 { _code; }
98 # define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
99 # define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
100
101
102 #define DEFINE_SIZE_STATIC(size) \
103 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
104 unsigned int get_size () const { return (size); } \
105 static constexpr unsigned null_size = (size); \
106 static constexpr unsigned min_size = (size); \
107 static constexpr unsigned static_size = (size)
108
109 #define DEFINE_SIZE_UNION(size, _member) \
110 DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
111 DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
112 static constexpr unsigned null_size = (size); \
113 static constexpr unsigned min_size = (size)
114
115 #define DEFINE_SIZE_MIN(size) \
116 DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
117 static constexpr unsigned null_size = (size); \
118 static constexpr unsigned min_size = (size)
119
120 #define DEFINE_SIZE_UNBOUNDED(size) \
121 DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
122 static constexpr unsigned min_size = (size)
123
124 #define DEFINE_SIZE_ARRAY(size, array) \
125 DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
126 DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + (HB_VAR_ARRAY+0) * sizeof ((array)[0])) \
127 static constexpr unsigned null_size = (size); \
128 static constexpr unsigned min_size = (size)
129
130 #define DEFINE_SIZE_ARRAY_SIZED(size, array) \
131 unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
132 DEFINE_SIZE_ARRAY(size, array)
133
134
135
136 /*
137 * Lazy loaders.
138 *
139 * The lazy-loaders are thread-safe pointer-like objects that create their
140 * instead on-demand. They also support access to a "data" object that is
141 * necessary for creating their instance. The data object, if specified,
142 * is accessed via pointer math, located at a location before the position
143 * of the loader itself. This avoids having to store a pointer to data
144 * for every lazy-loader. Multiple lazy-loaders can access the same data.
145 */
146
147 template <typename Data, unsigned int WheresData>
148 struct hb_data_wrapper_t
149 {
150 static_assert (WheresData > 0, "");
151
get_datahb_data_wrapper_t152 Data * get_data () const
153 { return *(((Data **) (void *) this) - WheresData); }
154
is_inerthb_data_wrapper_t155 bool is_inert () const { return !get_data (); }
156
157 template <typename Stored, typename Subclass>
call_createhb_data_wrapper_t158 Stored * call_create () const { return Subclass::create (get_data ()); }
159 };
160 template <>
161 struct hb_data_wrapper_t<void, 0>
162 {
is_inerthb_data_wrapper_t163 bool is_inert () const { return false; }
164
165 template <typename Stored, typename Funcs>
call_createhb_data_wrapper_t166 Stored * call_create () const { return Funcs::create (); }
167 };
168
169 template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
170 template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
171
172 template <typename Returned,
173 typename Subclass = void,
174 typename Data = void,
175 unsigned int WheresData = 0,
176 typename Stored = Returned>
177 struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
178 {
179 typedef typename hb_non_void_t<Subclass,
180 hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
181 >::value Funcs;
182
183 hb_lazy_loader_t () = default;
184 hb_lazy_loader_t (const hb_lazy_loader_t &other) = delete;
185
init0hb_lazy_loader_t186 void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
inithb_lazy_loader_t187 void init () { instance.set_relaxed (nullptr); }
finihb_lazy_loader_t188 void fini () { do_destroy (instance.get_acquire ()); init (); }
189
free_instancehb_lazy_loader_t190 void free_instance ()
191 {
192 retry:
193 Stored *p = instance.get_acquire ();
194 if (unlikely (p && !cmpexch (p, nullptr)))
195 goto retry;
196 do_destroy (p);
197 }
198
do_destroyhb_lazy_loader_t199 static void do_destroy (Stored *p)
200 {
201 if (p && p != const_cast<Stored *> (Funcs::get_null ()))
202 Funcs::destroy (p);
203 }
204
operator ->hb_lazy_loader_t205 const Returned * operator -> () const { return get (); }
206 template <typename U = Returned, hb_enable_if (!hb_is_same (U, void))>
operator *hb_lazy_loader_t207 const U & operator * () const { return *get (); }
operator boolhb_lazy_loader_t208 explicit operator bool () const
209 { return get_stored () != Funcs::get_null (); }
operator const C*hb_lazy_loader_t210 template <typename C> operator const C * () const { return get (); }
211
get_storedhb_lazy_loader_t212 Stored * get_stored () const
213 {
214 retry:
215 Stored *p = this->instance.get_acquire ();
216 if (unlikely (!p))
217 {
218 if (unlikely (this->is_inert ()))
219 return const_cast<Stored *> (Funcs::get_null ());
220
221 p = this->template call_create<Stored, Funcs> ();
222 if (unlikely (!p))
223 p = const_cast<Stored *> (Funcs::get_null ());
224
225 if (unlikely (!cmpexch (nullptr, p)))
226 {
227 do_destroy (p);
228 goto retry;
229 }
230 }
231 return p;
232 }
get_stored_relaxedhb_lazy_loader_t233 Stored * get_stored_relaxed () const
234 {
235 return this->instance.get_relaxed ();
236 }
237
cmpexchhb_lazy_loader_t238 bool cmpexch (Stored *current, Stored *value) const
239 {
240 /* This function can only be safely called directly if no
241 * other thread is accessing. */
242 return this->instance.cmpexch (current, value);
243 }
244
gethb_lazy_loader_t245 const Returned * get () const { return Funcs::convert (get_stored ()); }
get_relaxedhb_lazy_loader_t246 const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
get_unconsthb_lazy_loader_t247 Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
248
249 /* To be possibly overloaded by subclasses. */
converthb_lazy_loader_t250 static Returned* convert (Stored *p) { return p; }
251
252 /* By default null/init/fini the object. */
get_nullhb_lazy_loader_t253 static const Stored* get_null () { return &Null (Stored); }
createhb_lazy_loader_t254 static Stored *create (Data *data)
255 {
256 Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
257 if (likely (p))
258 p = new (p) Stored (data);
259 return p;
260 }
createhb_lazy_loader_t261 static Stored *create ()
262 {
263 Stored *p = (Stored *) hb_calloc (1, sizeof (Stored));
264 if (likely (p))
265 p = new (p) Stored ();
266 return p;
267 }
destroyhb_lazy_loader_t268 static void destroy (Stored *p)
269 {
270 p->~Stored ();
271 hb_free (p);
272 }
273
274 private:
275 /* Must only have one pointer. */
276 hb_atomic_ptr_t<Stored *> instance;
277 };
278
279 /* Specializations. */
280
281 template <typename T, unsigned int WheresFace>
282 struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
283 hb_face_lazy_loader_t<T, WheresFace>,
284 hb_face_t, WheresFace>
285 {
286 // Hack; have them here for API parity with hb_table_lazy_loader_t
get_blobhb_face_lazy_loader_t287 hb_blob_t *get_blob () { return this->get ()->get_blob (); }
288 };
289
290 template <typename T, unsigned int WheresFace, bool core=false>
291 struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
292 hb_table_lazy_loader_t<T, WheresFace, core>,
293 hb_face_t, WheresFace,
294 hb_blob_t>
295 {
createhb_table_lazy_loader_t296 static hb_blob_t *create (hb_face_t *face)
297 {
298 hb_sanitize_context_t c;
299 if (core)
300 c.set_num_glyphs (0); // So we don't recurse ad infinitum, or doesn't need num_glyphs
301 return c.reference_table<T> (face);
302 }
destroyhb_table_lazy_loader_t303 static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }
304
get_nullhb_table_lazy_loader_t305 static const hb_blob_t *get_null ()
306 { return hb_blob_get_empty (); }
307
converthb_table_lazy_loader_t308 static const T* convert (const hb_blob_t *blob)
309 { return blob->as<T> (); }
310
get_blobhb_table_lazy_loader_t311 hb_blob_t* get_blob () const { return this->get_stored (); }
312 };
313
314 #define HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T(Type) \
315 template <typename Subclass> \
316 struct hb_##Type##_funcs_lazy_loader_t : hb_lazy_loader_t<hb_##Type##_funcs_t, Subclass> \
317 { \
318 static void destroy (hb_##Type##_funcs_t *p) \
319 { hb_##Type##_funcs_destroy (p); } \
320 static const hb_##Type##_funcs_t *get_null () \
321 { return hb_##Type##_funcs_get_empty (); } \
322 }
323
324 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (font);
325 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (unicode);
326 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (draw);
327 HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T (paint);
328
329 #undef HB_DEFINE_TYPE_FUNCS_LAZY_LOADER_T
330
331
332 #endif /* HB_MACHINERY_HH */
333