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: [email protected] (Lode Vandevenne)
17 Author: [email protected] (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
ZopfliInitCache(size_t blocksize,ZopfliLongestMatchCache * lmc)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 if(lmc->sublen == NULL) {
35 fprintf(stderr,
36 "Error: Out of memory. Tried allocating %lu bytes of memory.\n",
37 (unsigned long)ZOPFLI_CACHE_LENGTH * 3 * blocksize);
38 exit (EXIT_FAILURE);
39 }
40
41 /* length > 0 and dist 0 is invalid combination, which indicates on purpose
42 that this cache value is not filled in yet. */
43 for (i = 0; i < blocksize; i++) lmc->length[i] = 1;
44 for (i = 0; i < blocksize; i++) lmc->dist[i] = 0;
45 for (i = 0; i < ZOPFLI_CACHE_LENGTH * blocksize * 3; i++) lmc->sublen[i] = 0;
46 }
47
ZopfliCleanCache(ZopfliLongestMatchCache * lmc)48 void ZopfliCleanCache(ZopfliLongestMatchCache* lmc) {
49 free(lmc->length);
50 free(lmc->dist);
51 free(lmc->sublen);
52 }
53
ZopfliSublenToCache(const unsigned short * sublen,size_t pos,size_t length,ZopfliLongestMatchCache * lmc)54 void ZopfliSublenToCache(const unsigned short* sublen,
55 size_t pos, size_t length,
56 ZopfliLongestMatchCache* lmc) {
57 size_t i;
58 size_t j = 0;
59 unsigned bestlength = 0;
60 unsigned char* cache;
61
62 #if ZOPFLI_CACHE_LENGTH == 0
63 return;
64 #endif
65
66 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
67 if (length < 3) return;
68 for (i = 3; i <= length; i++) {
69 if (i == length || sublen[i] != sublen[i + 1]) {
70 cache[j * 3] = i - 3;
71 cache[j * 3 + 1] = sublen[i] % 256;
72 cache[j * 3 + 2] = (sublen[i] >> 8) % 256;
73 bestlength = i;
74 j++;
75 if (j >= ZOPFLI_CACHE_LENGTH) break;
76 }
77 }
78 if (j < ZOPFLI_CACHE_LENGTH) {
79 assert(bestlength == length);
80 cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] = bestlength - 3;
81 } else {
82 assert(bestlength <= length);
83 }
84 assert(bestlength == ZopfliMaxCachedSublen(lmc, pos, length));
85 }
86
ZopfliCacheToSublen(const ZopfliLongestMatchCache * lmc,size_t pos,size_t length,unsigned short * sublen)87 void ZopfliCacheToSublen(const ZopfliLongestMatchCache* lmc,
88 size_t pos, size_t length,
89 unsigned short* sublen) {
90 size_t i, j;
91 unsigned maxlength = ZopfliMaxCachedSublen(lmc, pos, length);
92 unsigned prevlength = 0;
93 unsigned char* cache;
94 #if ZOPFLI_CACHE_LENGTH == 0
95 return;
96 #endif
97 if (length < 3) return;
98 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
99 for (j = 0; j < ZOPFLI_CACHE_LENGTH; j++) {
100 unsigned length = cache[j * 3] + 3;
101 unsigned dist = cache[j * 3 + 1] + 256 * cache[j * 3 + 2];
102 for (i = prevlength; i <= length; i++) {
103 sublen[i] = dist;
104 }
105 if (length == maxlength) break;
106 prevlength = length + 1;
107 }
108 }
109
110 /*
111 Returns the length up to which could be stored in the cache.
112 */
ZopfliMaxCachedSublen(const ZopfliLongestMatchCache * lmc,size_t pos,size_t length)113 unsigned ZopfliMaxCachedSublen(const ZopfliLongestMatchCache* lmc,
114 size_t pos, size_t length) {
115 unsigned char* cache;
116 #if ZOPFLI_CACHE_LENGTH == 0
117 return 0;
118 #endif
119 cache = &lmc->sublen[ZOPFLI_CACHE_LENGTH * pos * 3];
120 (void)length;
121 if (cache[1] == 0 && cache[2] == 0) return 0; /* No sublen cached. */
122 return cache[(ZOPFLI_CACHE_LENGTH - 1) * 3] + 3;
123 }
124
125 #endif /* ZOPFLI_LONGEST_MATCH_CACHE */
126