4 * XPRESS compression routines.
6 * See the comments in xpress-decompress.c about the XPRESS format.
10 * Copyright (C) 2012, 2013 Eric Biggers
12 * This file is part of wimlib, a library for working with WIM files.
14 * wimlib is free software; you can redistribute it and/or modify it under the
15 * terms of the GNU General Public License as published by the Free
16 * Software Foundation; either version 3 of the License, or (at your option)
19 * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
20 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
21 * A PARTICULAR PURPOSE. See the GNU General Public License for more
24 * You should have received a copy of the GNU General Public License
25 * along with wimlib; if not, see http://www.gnu.org/licenses/.
33 #include "wimlib/assert.h"
34 #include "wimlib/compressor_ops.h"
35 #include "wimlib/compress_common.h"
36 #include "wimlib/error.h"
37 #include "wimlib/lz_hash.h"
38 #include "wimlib/util.h"
39 #include "wimlib/xpress.h"
47 struct xpress_record_ctx {
48 input_idx_t freqs[XPRESS_NUM_SYMBOLS];
49 struct xpress_match *matches;
52 struct xpress_compressor {
55 struct xpress_match *matches;
56 input_idx_t *prev_tab;
57 u16 codewords[XPRESS_NUM_SYMBOLS];
58 u8 lens[XPRESS_NUM_SYMBOLS];
59 struct xpress_record_ctx record_ctx;
62 /* Intermediate XPRESS match/literal representation. */
64 u16 adjusted_len; /* Match length minus XPRESS_MIN_MATCH_LEN */
65 u16 offset; /* Match offset */
66 /* For literals, offset == 0 and adjusted_len is the literal. */
70 * Writes @match, which is a match given in the intermediate representation for
71 * XPRESS matches, to the output stream @ostream.
73 * @codewords and @lens provide the Huffman code that is being used.
76 xpress_write_match(struct xpress_match match,
77 struct output_bitstream *restrict ostream,
78 const u16 codewords[restrict],
79 const u8 lens[restrict])
81 u8 len_hdr = min(match.adjusted_len, 0xf);
82 u8 offset_bsr = bsr32(match.offset);
83 unsigned sym = XPRESS_NUM_CHARS + ((offset_bsr << 4) | len_hdr);
85 bitstream_put_bits(ostream, codewords[sym], lens[sym]);
87 if (match.adjusted_len >= 0xf) {
88 u8 byte1 = min(match.adjusted_len - 0xf, 0xff);
89 bitstream_put_byte(ostream, byte1);
91 bitstream_put_byte(ostream, match.adjusted_len & 0xff);
92 bitstream_put_byte(ostream, match.adjusted_len >> 8);
95 bitstream_put_bits(ostream, match.offset ^ (1U << offset_bsr), offset_bsr);
99 xpress_write_matches_and_literals(struct output_bitstream *ostream,
100 const struct xpress_match matches[restrict],
101 input_idx_t num_matches,
102 const u16 codewords[restrict],
103 const u8 lens[restrict])
105 for (input_idx_t i = 0; i < num_matches; i++) {
106 if (matches[i].offset) {
108 xpress_write_match(matches[i], ostream, codewords, lens);
111 u8 lit = matches[i].adjusted_len;
112 bitstream_put_bits(ostream, codewords[lit], lens[lit]);
115 bitstream_put_bits(ostream, codewords[XPRESS_END_OF_DATA], lens[XPRESS_END_OF_DATA]);
119 xpress_record_literal(u8 lit, void *_ctx)
121 struct xpress_record_ctx *ctx = _ctx;
123 *(ctx->matches++) = (struct xpress_match) { .offset = 0, .adjusted_len = lit };
127 xpress_record_match(unsigned len, unsigned offset, void *_ctx)
129 struct xpress_record_ctx *ctx = _ctx;
131 XPRESS_ASSERT(len >= XPRESS_MIN_MATCH_LEN);
132 XPRESS_ASSERT(len <= XPRESS_MAX_MATCH_LEN);
133 XPRESS_ASSERT(offset >= XPRESS_MIN_OFFSET);
134 XPRESS_ASSERT(offset <= XPRESS_MAX_OFFSET);
136 unsigned adjusted_len = len - XPRESS_MIN_MATCH_LEN;
137 unsigned len_hdr = min(adjusted_len, 0xf);
138 unsigned sym = XPRESS_NUM_CHARS + ((bsr32(offset) << 4) | len_hdr);
140 XPRESS_ASSERT(sym >= XPRESS_NUM_CHARS);
141 XPRESS_ASSERT(sym < XPRESS_NUM_SYMBOLS);
144 *(ctx->matches++) = (struct xpress_match) { .offset = offset,
145 .adjusted_len = adjusted_len };
148 static const struct lz_params xpress_lz_params = {
149 .min_match = XPRESS_MIN_MATCH_LEN,
150 .max_match = XPRESS_MAX_MATCH_LEN,
151 .max_offset = XPRESS_MAX_OFFSET,
155 .max_lazy_match = 16,
160 xpress_compress(const void *uncompressed_data, size_t uncompressed_size,
161 void *compressed_data, size_t compressed_size_avail, void *_c)
163 struct xpress_compressor *c = _c;
164 u8 *cptr = compressed_data;
165 struct output_bitstream ostream;
166 input_idx_t num_matches;
168 size_t compressed_size;
170 /* XPRESS requires 256 bytes of overhead for the Huffman code, so it's
171 * impossible to compress 256 bytes or less of data to less than the
174 * +1 to take into account that the buffer for compressed data is 1 byte
175 * smaller than the buffer for uncompressed data.
177 * +4 to take into account that init_output_bitstream() requires at
178 * least 4 bytes of data. */
179 if (compressed_size_avail < XPRESS_NUM_SYMBOLS / 2 + 1 + 4)
182 /* Copy the data to a temporary buffer, but only to avoid
183 * inconsequential accesses of uninitialized memory in
184 * lz_analyze_block(). */
185 memcpy(c->window, uncompressed_data, uncompressed_size);
186 memset(c->window + uncompressed_size, 0, 8);
188 /* Determine match/literal sequence to divide the data into. */
189 memset(c->record_ctx.freqs, 0, sizeof(c->record_ctx.freqs));
190 c->record_ctx.matches = c->matches;
191 lz_analyze_block(c->window,
194 xpress_record_literal,
199 num_matches = (c->record_ctx.matches - c->matches);
201 /* Account for end of data symbol. */
202 c->record_ctx.freqs[XPRESS_END_OF_DATA]++;
204 /* Build the Huffman code. */
205 make_canonical_huffman_code(XPRESS_NUM_SYMBOLS, XPRESS_MAX_CODEWORD_LEN,
206 c->record_ctx.freqs, c->lens, c->codewords);
208 /* Output the Huffman code as a series of 512 4-bit lengths. */
209 for (i = 0; i < XPRESS_NUM_SYMBOLS; i += 2)
210 *cptr++ = (c->lens[i] & 0xf) | (c->lens[i + 1] << 4);
212 /* Output the encoded matches/literals. */
213 init_output_bitstream(&ostream, cptr,
214 compressed_size_avail - XPRESS_NUM_SYMBOLS / 2 - 1);
216 xpress_write_matches_and_literals(&ostream, c->matches,
217 num_matches, c->codewords, c->lens);
219 /* Flush any pending data and get the length of the compressed data. */
220 compressed_size = flush_output_bitstream(&ostream);
221 if (compressed_size == ~(input_idx_t)0)
224 compressed_size += XPRESS_NUM_SYMBOLS / 2;
226 #if defined(ENABLE_XPRESS_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION)
227 /* Verify that we really get the same thing back when decompressing. */
229 struct wimlib_decompressor *decompressor;
231 if (0 == wimlib_create_decompressor(WIMLIB_COMPRESSION_TYPE_XPRESS,
237 ret = wimlib_decompress(compressed_data,
242 wimlib_free_decompressor(decompressor);
245 ERROR("Failed to decompress data we "
246 "compressed using XPRESS algorithm");
250 if (memcmp(uncompressed_data, c->window,
253 ERROR("Data we compressed using XPRESS algorithm "
254 "didn't decompress to original");
259 WARNING("Failed to create decompressor for "
260 "data verification!");
265 return compressed_size;
269 xpress_free_compressor(void *_c)
271 struct xpress_compressor *c = _c;
282 xpress_create_compressor(size_t max_window_size,
283 const struct wimlib_compressor_params_header *params,
286 struct xpress_compressor *c;
288 if (max_window_size == 0 || max_window_size > (1U << 26))
289 return WIMLIB_ERR_INVALID_PARAM;
291 c = CALLOC(1, sizeof(struct xpress_compressor));
295 c->window = MALLOC(max_window_size + 8);
296 if (c->window == NULL)
299 c->max_window_size = max_window_size;
301 c->matches = MALLOC(max_window_size * sizeof(c->matches[0]));
302 if (c->matches == NULL)
305 c->prev_tab = MALLOC(max_window_size * sizeof(c->prev_tab[0]));
306 if (c->prev_tab == NULL)
313 xpress_free_compressor(c);
314 return WIMLIB_ERR_NOMEM;
318 xpress_get_needed_memory(size_t max_window_size,
319 const struct wimlib_compressor_params_header *params)
323 size += sizeof(struct xpress_compressor);
324 size += max_window_size + 8;
325 size += max_window_size * sizeof(((struct xpress_compressor*)0)->matches[0]);
326 size += max_window_size * sizeof(((struct xpress_compressor*)0)->prev_tab[0]);
331 const struct compressor_ops xpress_compressor_ops = {
332 .get_needed_memory = xpress_get_needed_memory,
333 .create_compressor = xpress_create_compressor,
334 .compress = xpress_compress,
335 .free_compressor = xpress_free_compressor,