1 /* 2 Copyright 2011 Google Inc. All Rights Reserved. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 16 Author: lode.vandevenne (at) gmail.com (Lode Vandevenne) 17 Author: jyrki.alakuijala (at) gmail.com (Jyrki Alakuijala) 18 */ 19 20 #include "cache.h" 21 22 #include <assert.h> 23 #include <stdio.h> 24 #include <stdlib.h> 25 26 #ifdef ZOPFLI_LONGEST_MATCH_CACHE 27 28 void ZopfliInitCache(size_t blocksize, ZopfliLongestMatchCache* lmc) { 29 size_t i; 30 lmc->length = (unsigned short*)malloc(sizeof(unsigned short) * blocksize); 31 lmc->dist = (unsigned short*)malloc(sizeof(unsigned short) * blocksize); 32 /* Rather large amount of memory. */ 33 lmc->sublen = (unsigned char*)malloc(ZOPFLI_CACHE_LENGTH * 3 * blocksize); 34 35 /* length > 0 and dist 0 is invalid combination, which indicates on purpose 36 that this cache value is not filled in yet. */ 37 for (i = 0; i < blocksize; i++) lmc->length[i] = 1; 38 for (i = 0; i < blocksize; i++) lmc->dist[i] = 0; 39 for (i = 0; i < ZOPFLI_CACHE_LENGTH * blocksize * 3; i++) lmc->sublen[i] = 0; 40 } 41 42 void ZopfliCleanCache(ZopfliLongestMatchCache* lmc) { 43 free(lmc->length); 44 free(lmc->dist); 45 free(lmc->sublen); 46 } 47 48 void ZopfliSublenToCache(const unsigned short* sublen, 49 size_t pos, size_t length, 50 ZopfliLongestMatchCache* lmc) { 51 size_t i; 52 size_t j = 0; 53 unsigned bestlength = 0; 54 unsigned char* cache; 55 56 #if ZOPFLI_CACHE_LENGTH == 0 57 return; 58 #endif 59 60 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3]; 61 if (length < 3) return; 62 for (i = 3; i <= length; i++) { 63 if (i == length || sublen[i] != sublen[i + 1]) { 64 cache[j * 3] = i - 3; 65 cache[j * 3 + 1] = sublen[i] % 256; 66 cache[j * 3 + 2] = (sublen[i] >> 8) % 256; 67 bestlength = i; 68 j++; 69 if (j >= ZOPFLI_CACHE_LENGTH) break; 70 } 71 } 72 if (j < ZOPFLI_CACHE_LENGTH) { 73 assert(bestlength == length); 74 cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] = bestlength - 3; 75 } else { 76 assert(bestlength <= length); 77 } 78 assert(bestlength == ZopfliMaxCachedSublen(lmc, pos, length)); 79 } 80 81 void ZopfliCacheToSublen(const ZopfliLongestMatchCache* lmc, 82 size_t pos, size_t length, 83 unsigned short* sublen) { 84 size_t i, j; 85 unsigned maxlength = ZopfliMaxCachedSublen(lmc, pos, length); 86 unsigned prevlength = 0; 87 unsigned char* cache; 88 #if ZOPFLI_CACHE_LENGTH == 0 89 return; 90 #endif 91 if (length < 3) return; 92 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3]; 93 for (j = 0; j < ZOPFLI_CACHE_LENGTH; j++) { 94 unsigned length = cache[j * 3] + 3; 95 unsigned dist = cache[j * 3 + 1] + 256 * cache[j * 3 + 2]; 96 for (i = prevlength; i <= length; i++) { 97 sublen[i] = dist; 98 } 99 if (length == maxlength) break; 100 prevlength = length + 1; 101 } 102 } 103 104 /* 105 Returns the length up to which could be stored in the cache. 106 */ 107 unsigned ZopfliMaxCachedSublen(const ZopfliLongestMatchCache* lmc, 108 size_t pos, size_t length) { 109 unsigned char* cache; 110 #if ZOPFLI_CACHE_LENGTH == 0 111 return 0; 112 #endif 113 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3]; 114 (void)length; 115 if (cache[1] == 0 && cache[2] == 0) return 0; /* No sublen cached. */ 116 return cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] + 3; 117 } 118 119 #endif /* ZOPFLI_LONGEST_MATCH_CACHE */ 120
