1 /* SPDX-License-Identifier: GPL-2.0-or-later */
3  * decompress_common.h - Code shared by the XPRESS and LZX decompressors
21 /* Enable whole-word match copying on selected architectures  */
36 /* Generate a "word" with platform-dependent size whose bytes all contain the
50 /* Structure that encapsulates a block of in-memory data being interpreted as a
52  * to be stored in little endian 16-bit coding units, with the bits ordered high
58 	 * left-justified; the next bit is always bit 31.
76 	is->bitbuf = 0;  in init_input_bitstream()
77 	is->bitsleft = 0;  in init_input_bitstream()
78 	is->next = buffer;  in init_input_bitstream()
79 	is->end = is->next + size;  in init_input_bitstream()
90 	if (is->bitsleft < num_bits) {  in bitstream_ensure_bits()
91 		if (is->end - is->next >= 2) {  in bitstream_ensure_bits()
92 			is->bitbuf |= (u32)get_unaligned_le16(is->next)  in bitstream_ensure_bits()
93 					<< (16 - is->bitsleft);  in bitstream_ensure_bits()
94 			is->next += 2;  in bitstream_ensure_bits()
96 		is->bitsleft += 16;  in bitstream_ensure_bits()
107 	return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1);  in bitstream_peek_bits()
117 	is->bitbuf <<= num_bits;  in bitstream_remove_bits()
118 	is->bitsleft -= num_bits;  in bitstream_remove_bits()
146 	if (unlikely(is->end == is->next))  in bitstream_read_byte()
148 	return *is->next++;  in bitstream_read_byte()
151 /* Read and return the next 16-bit integer embedded in the bitstream.  */
157 	if (unlikely(is->end - is->next < 2))  in bitstream_read_u16()
159 	v = get_unaligned_le16(is->next);  in bitstream_read_u16()
160 	is->next += 2;  in bitstream_read_u16()
164 /* Read and return the next 32-bit integer embedded in the bitstream.  */
170 	if (unlikely(is->end - is->next < 4))  in bitstream_read_u32()
172 	v = get_unaligned_le32(is->next);  in bitstream_read_u32()
173 	is->next += 4;  in bitstream_read_u32()
184 	if ((size_t)(is->end - is->next) < count)  in bitstream_read_bytes()
186 	memcpy(dst_buffer, is->next, count);  in bitstream_read_bytes()
187 	is->next += count;  in bitstream_read_bytes()
191 /* Align the input bitstream on a coding-unit boundary.  */
194 	is->bitsleft = 0;  in bitstream_align()
195 	is->bitbuf = 0;  in bitstream_align()
204 /* Reads and returns the next Huffman-encoded symbol from a bitstream.  If the
218 	/* Index the decode table by the next table_bits bits of the input.  */  in read_huffsym()
223 		 * symbol and codeword length.  The low 11 bits are the  in read_huffsym()
224 		 * symbol, and the high 5 bits are the codeword length.  in read_huffsym()
229 	/* Slow case: The codeword for the symbol is longer than  in read_huffsym()
233 	 * bit-by-bit to decode the symbol.  in read_huffsym()
243  * Copy an LZ77 match at (dst - offset) to dst.
245  * The length and offset must be already validated --- that is, (dst - offset)
257 	const u8 *src = dst - offset;  in lz_copy()
262 	 * near-random and all the matches have very short lengths.  Note that  in lz_copy()
269 	 * beyond the end of the output buffer, hence the check for (bufend -  in lz_copy()
270 	 * end >= WORDBYTES - 1).  in lz_copy()
275 	if (bufend - end >= (ptrdiff_t)(WORDBYTES - 1)) {  in lz_copy()
301 			/* Offset 1 matches are equivalent to run-length  in lz_copy()
305 			size_t v = repeat_byte(*(dst - 1));  in lz_copy()
330 		length--;  in lz_copy()
334 		length--;  in lz_copy()
338 	} while (--length);  in lz_copy()