1/*
2Copyright 2011 Google Inc. All Rights Reserved.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15
16Author: lode.vandevenne@gmail.com (Lode Vandevenne)
17Author: jyrki.alakuijala@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
28void 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
42void ZopfliCleanCache(ZopfliLongestMatchCache* lmc) {
43  free(lmc->length);
44  free(lmc->dist);
45  free(lmc->sublen);
46}
47
48void 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
81void 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/*
105Returns the length up to which could be stored in the cache.
106*/
107unsigned 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