wimlib.net Git - wimlib/blob - src/xpress-compress.c

   1 /*
   2  * xpress-compress.c
   3  *
   4  * XPRESS compression routines.
   5  *
   6  * See the comments in xpress-decompress.c about the XPRESS format.
   7  */
   8
   9 /*
  10  * Copyright (C) 2012, 2013 Eric Biggers
  11  *
  12  * This file is part of wimlib, a library for working with WIM files.
  13  *
  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)
  17  * any later version.
  18  *
  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
  22  * details.
  23  *
  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/.
  26  */
  27
  28 #ifdef HAVE_CONFIG_H
  29 #  include "config.h"
  30 #endif
  31
  32 #include "wimlib.h"
  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"
  40
  41 #include <string.h>
  42
  43 struct xpress_record_ctx {
  44         input_idx_t freqs[XPRESS_NUM_SYMBOLS];
  45         struct xpress_match *matches;
  46 };
  47
  48 struct xpress_compressor {
  49         u8 *window;
  50         u32 max_window_size;
  51         struct xpress_match *matches;
  52         input_idx_t *prev_tab;
  53         u16 codewords[XPRESS_NUM_SYMBOLS];
  54         u8 lens[XPRESS_NUM_SYMBOLS];
  55         struct xpress_record_ctx record_ctx;
  56 };
  57
  58 /* Intermediate XPRESS match/literal representation.  */
  59 struct xpress_match {
  60         u16 adjusted_len;  /* Match length minus XPRESS_MIN_MATCH_LEN */
  61         u16 offset;        /* Match offset */
  62         /* For literals, offset == 0 and adjusted_len is the literal.  */
  63 };
  64
  65 /*
  66  * Writes @match, which is a match given in the intermediate representation for
  67  * XPRESS matches, to the output stream @ostream.
  68  *
  69  * @codewords and @lens provide the Huffman code that is being used.
  70  */
  71 static void
  72 xpress_write_match(struct xpress_match match,
  73                    struct output_bitstream *restrict ostream,
  74                    const u16 codewords[restrict],
  75                    const u8 lens[restrict])
  76 {
  77         u8 len_hdr = min(match.adjusted_len, 0xf);
  78         u8 offset_bsr = bsr32(match.offset);
  79         unsigned sym = XPRESS_NUM_CHARS + ((offset_bsr << 4) | len_hdr);
  80
  81         bitstream_put_bits(ostream, codewords[sym], lens[sym]);
  82
  83         if (match.adjusted_len >= 0xf) {
  84                 u8 byte1 = min(match.adjusted_len - 0xf, 0xff);
  85                 bitstream_put_byte(ostream, byte1);
  86                 if (byte1 == 0xff) {
  87                         bitstream_put_byte(ostream, match.adjusted_len & 0xff);
  88                         bitstream_put_byte(ostream, match.adjusted_len >> 8);
  89                 }
  90         }
  91         bitstream_put_bits(ostream, match.offset ^ (1U << offset_bsr), offset_bsr);
  92 }
  93
  94 static void
  95 xpress_write_matches_and_literals(struct output_bitstream *ostream,
  96                                   const struct xpress_match matches[restrict],
  97                                   input_idx_t num_matches,
  98                                   const u16 codewords[restrict],
  99                                   const u8 lens[restrict])
 100 {
 101         for (input_idx_t i = 0; i < num_matches; i++) {
 102                 if (matches[i].offset) {
 103                         /* Real match  */
 104                         xpress_write_match(matches[i], ostream, codewords, lens);
 105                 } else {
 106                         /* Literal byte  */
 107                         u8 lit = matches[i].adjusted_len;
 108                         bitstream_put_bits(ostream, codewords[lit], lens[lit]);
 109                 }
 110         }
 111         bitstream_put_bits(ostream, codewords[XPRESS_END_OF_DATA], lens[XPRESS_END_OF_DATA]);
 112 }
 113
 114 static void
 115 xpress_record_literal(u8 lit, void *_ctx)
 116 {
 117         struct xpress_record_ctx *ctx = _ctx;
 118         ctx->freqs[lit]++;
 119         *(ctx->matches++) = (struct xpress_match) { .offset = 0, .adjusted_len = lit };
 120 }
 121
 122 static void
 123 xpress_record_match(unsigned len, unsigned offset, void *_ctx)
 124 {
 125         struct xpress_record_ctx *ctx = _ctx;
 126
 127         XPRESS_ASSERT(len >= XPRESS_MIN_MATCH_LEN);
 128         XPRESS_ASSERT(len <= XPRESS_MAX_MATCH_LEN);
 129         XPRESS_ASSERT(offset >= XPRESS_MIN_OFFSET);
 130         XPRESS_ASSERT(offset <= XPRESS_MAX_OFFSET);
 131
 132         unsigned adjusted_len = len - XPRESS_MIN_MATCH_LEN;
 133         unsigned len_hdr = min(adjusted_len, 0xf);
 134         unsigned sym = XPRESS_NUM_CHARS + ((bsr32(offset) << 4) | len_hdr);
 135
 136         XPRESS_ASSERT(sym >= XPRESS_NUM_CHARS);
 137         XPRESS_ASSERT(sym < XPRESS_NUM_SYMBOLS);
 138
 139         ctx->freqs[sym]++;
 140         *(ctx->matches++) = (struct xpress_match) { .offset = offset,
 141                                                     .adjusted_len = adjusted_len };
 142 }
 143
 144 static const struct lz_params xpress_lz_params = {
 145         .min_match      = XPRESS_MIN_MATCH_LEN,
 146         .max_match      = XPRESS_MAX_MATCH_LEN,
 147         .max_offset     = XPRESS_MAX_OFFSET,
 148         .good_match     = 16,
 149         .nice_match     = 32,
 150         .max_chain_len  = 16,
 151         .max_lazy_match = 16,
 152         .too_far        = 4096,
 153 };
 154
 155 static size_t
 156 xpress_compress(const void *uncompressed_data, size_t uncompressed_size,
 157                 void *compressed_data, size_t compressed_size_avail, void *_c)
 158 {
 159         struct xpress_compressor *c = _c;
 160         u8 *cptr = compressed_data;
 161         struct output_bitstream ostream;
 162         input_idx_t num_matches;
 163         input_idx_t i;
 164         size_t compressed_size;
 165
 166         /* XPRESS requires 256 bytes of overhead for the Huffman code, so it's
 167          * impossible to compress 256 bytes or less of data to less than the
 168          * input size.
 169          *
 170          * +1 to take into account that the buffer for compressed data is 1 byte
 171          * smaller than the buffer for uncompressed data.
 172          *
 173          * +4 to take into account that init_output_bitstream() requires at
 174          * least 4 bytes of data.  */
 175         if (compressed_size_avail < XPRESS_NUM_SYMBOLS / 2 + 1 + 4)
 176                 return 0;
 177
 178         /* Copy the data to a temporary buffer, but only to avoid
 179          * inconsequential accesses of uninitialized memory in
 180          * lz_analyze_block().  */
 181         memcpy(c->window, uncompressed_data, uncompressed_size);
 182         memset(c->window + uncompressed_size, 0, 8);
 183
 184         /* Determine match/literal sequence to divide the data into.  */
 185         memset(c->record_ctx.freqs, 0, sizeof(c->record_ctx.freqs));
 186         c->record_ctx.matches = c->matches;
 187         lz_analyze_block(c->window,
 188                          uncompressed_size,
 189                          xpress_record_match,
 190                          xpress_record_literal,
 191                          &c->record_ctx,
 192                          &xpress_lz_params,
 193                          c->prev_tab);
 194
 195         num_matches = (c->record_ctx.matches - c->matches);
 196
 197         /* Account for end of data symbol.  */
 198         c->record_ctx.freqs[XPRESS_END_OF_DATA]++;
 199
 200         /* Build the Huffman code.  */
 201         make_canonical_huffman_code(XPRESS_NUM_SYMBOLS, XPRESS_MAX_CODEWORD_LEN,
 202                                     c->record_ctx.freqs, c->lens, c->codewords);
 203
 204         /* Output the Huffman code as a series of 512 4-bit lengths.  */
 205         for (i = 0; i < XPRESS_NUM_SYMBOLS; i += 2)
 206                 *cptr++ = (c->lens[i] & 0xf) | (c->lens[i + 1] << 4);
 207
 208         /* Output the encoded matches/literals.  */
 209         init_output_bitstream(&ostream, cptr,
 210                               compressed_size_avail - XPRESS_NUM_SYMBOLS / 2 - 1);
 211
 212         xpress_write_matches_and_literals(&ostream, c->matches,
 213                                           num_matches, c->codewords, c->lens);
 214
 215         /* Flush any pending data and get the length of the compressed data.  */
 216         compressed_size = flush_output_bitstream(&ostream);
 217         if (compressed_size == ~(input_idx_t)0)
 218                 return 0;
 219
 220         compressed_size += XPRESS_NUM_SYMBOLS / 2;
 221
 222 #if defined(ENABLE_XPRESS_DEBUG) || defined(ENABLE_VERIFY_COMPRESSION)
 223         /* Verify that we really get the same thing back when decompressing.  */
 224         {
 225                 struct wimlib_decompressor *decompressor;
 226
 227                 if (0 == wimlib_create_decompressor(WIMLIB_COMPRESSION_TYPE_XPRESS,
 228                                                     c->max_window_size,
 229                                                     NULL,
 230                                                     &decompressor))
 231                 {
 232                         int ret;
 233                         ret = wimlib_decompress(compressed_data,
 234                                                 compressed_size,
 235                                                 c->window,
 236                                                 uncompressed_size,
 237                                                 decompressor);
 238                         wimlib_free_decompressor(decompressor);
 239
 240                         if (ret) {
 241                                 ERROR("Failed to decompress data we "
 242                                       "compressed using XPRESS algorithm");
 243                                 wimlib_assert(0);
 244                                 return 0;
 245                         }
 246                         if (memcmp(uncompressed_data, c->window,
 247                                    uncompressed_size))
 248                         {
 249                                 ERROR("Data we compressed using XPRESS algorithm "
 250                                       "didn't decompress to original");
 251                                 wimlib_assert(0);
 252                                 return 0;
 253                         }
 254                 } else {
 255                         WARNING("Failed to create decompressor for "
 256                                 "data verification!");
 257                 }
 258         }
 259 #endif
 260
 261         return compressed_size;
 262 }
 263
 264 static void
 265 xpress_free_compressor(void *_c)
 266 {
 267         struct xpress_compressor *c = _c;
 268
 269         if (c) {
 270                 FREE(c->window);
 271                 FREE(c->matches);
 272                 FREE(c->prev_tab);
 273                 FREE(c);
 274         }
 275 }
 276
 277 static int
 278 xpress_create_compressor(size_t max_window_size,
 279                          const struct wimlib_compressor_params_header *params,
 280                          void **c_ret)
 281 {
 282         struct xpress_compressor *c;
 283
 284         if (max_window_size == 0 || max_window_size > (1U << 26))
 285                 return WIMLIB_ERR_INVALID_PARAM;
 286
 287         c = CALLOC(1, sizeof(struct xpress_compressor));
 288         if (c == NULL)
 289                 goto oom;
 290
 291         c->window = MALLOC(max_window_size + 8);
 292         if (c->window == NULL)
 293                 goto oom;
 294
 295         c->max_window_size = max_window_size;
 296
 297         c->matches = MALLOC(max_window_size * sizeof(c->matches[0]));
 298         if (c->matches == NULL)
 299                 goto oom;
 300
 301         c->prev_tab = MALLOC(max_window_size * sizeof(c->prev_tab[0]));
 302         if (c->prev_tab == NULL)
 303                 goto oom;
 304
 305         *c_ret = c;
 306         return 0;
 307
 308 oom:
 309         xpress_free_compressor(c);
 310         return WIMLIB_ERR_NOMEM;
 311 }
 312
 313 static u64
 314 xpress_get_needed_memory(size_t max_window_size,
 315                          const struct wimlib_compressor_params_header *params)
 316 {
 317         u64 size = 0;
 318
 319         size += sizeof(struct xpress_compressor);
 320         size += max_window_size + 8;
 321         size += max_window_size * sizeof(((struct xpress_compressor*)0)->matches[0]);
 322         size += max_window_size * sizeof(((struct xpress_compressor*)0)->prev_tab[0]);
 323
 324         return size;
 325 }
 326
 327 const struct compressor_ops xpress_compressor_ops = {
 328         .get_needed_memory  = xpress_get_needed_memory,
 329         .create_compressor  = xpress_create_compressor,
 330         .compress           = xpress_compress,
 331         .free_compressor    = xpress_free_compressor,
 332 };