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126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
/*
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Copyright 2011 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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Author: lode.vandevenne@gmail.com (Lode Vandevenne)
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Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
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*/
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#include "cache.h"
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#ifdef ZOPFLI_LONGEST_MATCH_CACHE
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void ZopfliInitCache(size_t blocksize, ZopfliLongestMatchCache* lmc) {
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size_t i;
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lmc->length = (unsigned short*)malloc(sizeof(unsigned short) * blocksize);
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lmc->dist = (unsigned short*)malloc(sizeof(unsigned short) * blocksize);
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/* Rather large amount of memory. */
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lmc->sublen = (unsigned char*)malloc(ZOPFLI_CACHE_LENGTH * 3 * blocksize);
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if(lmc->sublen == NULL) {
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fprintf(stderr,
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"Error: Out of memory. Tried allocating %lu bytes of memory.\n",
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ZOPFLI_CACHE_LENGTH * 3 * blocksize);
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exit (EXIT_FAILURE);
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}
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/* length > 0 and dist 0 is invalid combination, which indicates on purpose
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that this cache value is not filled in yet. */
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for (i = 0; i < blocksize; i++) lmc->length[i] = 1;
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for (i = 0; i < blocksize; i++) lmc->dist[i] = 0;
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for (i = 0; i < ZOPFLI_CACHE_LENGTH * blocksize * 3; i++) lmc->sublen[i] = 0;
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}
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void ZopfliCleanCache(ZopfliLongestMatchCache* lmc) {
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free(lmc->length);
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free(lmc->dist);
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free(lmc->sublen);
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}
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void ZopfliSublenToCache(const unsigned short* sublen,
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size_t pos, size_t length,
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ZopfliLongestMatchCache* lmc) {
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size_t i;
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size_t j = 0;
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unsigned bestlength = 0;
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unsigned char* cache;
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#if ZOPFLI_CACHE_LENGTH == 0
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return;
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#endif
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cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
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if (length < 3) return;
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for (i = 3; i <= length; i++) {
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if (i == length || sublen[i] != sublen[i + 1]) {
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cache[j * 3] = i - 3;
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cache[j * 3 + 1] = sublen[i] % 256;
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cache[j * 3 + 2] = (sublen[i] >> 8) % 256;
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bestlength = i;
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j++;
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if (j >= ZOPFLI_CACHE_LENGTH) break;
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}
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}
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if (j < ZOPFLI_CACHE_LENGTH) {
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assert(bestlength == length);
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cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] = bestlength - 3;
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} else {
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assert(bestlength <= length);
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}
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assert(bestlength == ZopfliMaxCachedSublen(lmc, pos, length));
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}
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void ZopfliCacheToSublen(const ZopfliLongestMatchCache* lmc,
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size_t pos, size_t length,
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unsigned short* sublen) {
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size_t i, j;
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unsigned maxlength = ZopfliMaxCachedSublen(lmc, pos, length);
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unsigned prevlength = 0;
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unsigned char* cache;
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#if ZOPFLI_CACHE_LENGTH == 0
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return;
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#endif
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if (length < 3) return;
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cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
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for (j = 0; j < ZOPFLI_CACHE_LENGTH; j++) {
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unsigned length = cache[j * 3] + 3;
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unsigned dist = cache[j * 3 + 1] + 256 * cache[j * 3 + 2];
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for (i = prevlength; i <= length; i++) {
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sublen[i] = dist;
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}
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if (length == maxlength) break;
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prevlength = length + 1;
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}
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}
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/*
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Returns the length up to which could be stored in the cache.
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*/
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unsigned ZopfliMaxCachedSublen(const ZopfliLongestMatchCache* lmc,
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size_t pos, size_t length) {
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unsigned char* cache;
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#if ZOPFLI_CACHE_LENGTH == 0
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return 0;
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#endif
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cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
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(void)length;
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if (cache[1] == 0 && cache[2] == 0) return 0; /* No sublen cached. */
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return cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] + 3;
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}
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#endif /* ZOPFLI_LONGEST_MATCH_CACHE */
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