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@gmail.com (Lode Vandevenne)
17 Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
18 */
19
20 #include "hash.h"
21
22 #include <assert.h>
23 #include <stdio.h>
24 #include <stdlib.h>
25
26 #define HASH_SHIFT 5
27 #define HASH_MASK 32767
28
ZopfliInitHash(size_t window_size,ZopfliHash * h)29 void ZopfliInitHash(size_t window_size, ZopfliHash* h) {
30 size_t i;
31
32 h->val = 0;
33 h->head = (int*)malloc(sizeof(*h->head) * 65536);
34 h->prev = (unsigned short*)malloc(sizeof(*h->prev) * window_size);
35 h->hashval = (int*)malloc(sizeof(*h->hashval) * window_size);
36 for (i = 0; i < 65536; i++) {
37 h->head[i] = -1; /* -1 indicates no head so far. */
38 }
39 for (i = 0; i < window_size; i++) {
40 h->prev[i] = i; /* If prev[j] == j, then prev[j] is uninitialized. */
41 h->hashval[i] = -1;
42 }
43
44 #ifdef ZOPFLI_HASH_SAME
45 h->same = (unsigned short*)malloc(sizeof(*h->same) * window_size);
46 for (i = 0; i < window_size; i++) {
47 h->same[i] = 0;
48 }
49 #endif
50
51 #ifdef ZOPFLI_HASH_SAME_HASH
52 h->val2 = 0;
53 h->head2 = (int*)malloc(sizeof(*h->head2) * 65536);
54 h->prev2 = (unsigned short*)malloc(sizeof(*h->prev2) * window_size);
55 h->hashval2 = (int*)malloc(sizeof(*h->hashval2) * window_size);
56 for (i = 0; i < 65536; i++) {
57 h->head2[i] = -1;
58 }
59 for (i = 0; i < window_size; i++) {
60 h->prev2[i] = i;
61 h->hashval2[i] = -1;
62 }
63 #endif
64 }
65
ZopfliCleanHash(ZopfliHash * h)66 void ZopfliCleanHash(ZopfliHash* h) {
67 free(h->head);
68 free(h->prev);
69 free(h->hashval);
70
71 #ifdef ZOPFLI_HASH_SAME_HASH
72 free(h->head2);
73 free(h->prev2);
74 free(h->hashval2);
75 #endif
76
77 #ifdef ZOPFLI_HASH_SAME
78 free(h->same);
79 #endif
80 }
81
82 /*
83 Update the sliding hash value with the given byte. All calls to this function
84 must be made on consecutive input characters. Since the hash value exists out
85 of multiple input bytes, a few warmups with this function are needed initially.
86 */
UpdateHashValue(ZopfliHash * h,unsigned char c)87 static void UpdateHashValue(ZopfliHash* h, unsigned char c) {
88 h->val = (((h->val) << HASH_SHIFT) ^ (c)) & HASH_MASK;
89 }
90
ZopfliUpdateHash(const unsigned char * array,size_t pos,size_t end,ZopfliHash * h)91 void ZopfliUpdateHash(const unsigned char* array, size_t pos, size_t end,
92 ZopfliHash* h) {
93 unsigned short hpos = pos & ZOPFLI_WINDOW_MASK;
94 #ifdef ZOPFLI_HASH_SAME
95 size_t amount = 0;
96 #endif
97
98 UpdateHashValue(h, pos + ZOPFLI_MIN_MATCH <= end ?
99 array[pos + ZOPFLI_MIN_MATCH - 1] : 0);
100 h->hashval[hpos] = h->val;
101 if (h->head[h->val] != -1 && h->hashval[h->head[h->val]] == h->val) {
102 h->prev[hpos] = h->head[h->val];
103 }
104 else h->prev[hpos] = hpos;
105 h->head[h->val] = hpos;
106
107 #ifdef ZOPFLI_HASH_SAME
108 /* Update "same". */
109 if (h->same[(pos - 1) & ZOPFLI_WINDOW_MASK] > 1) {
110 amount = h->same[(pos - 1) & ZOPFLI_WINDOW_MASK] - 1;
111 }
112 while (pos + amount + 1 < end &&
113 array[pos] == array[pos + amount + 1] && amount < (unsigned short)(-1)) {
114 amount++;
115 }
116 h->same[hpos] = amount;
117 #endif
118
119 #ifdef ZOPFLI_HASH_SAME_HASH
120 h->val2 = ((h->same[hpos] - ZOPFLI_MIN_MATCH) & 255) ^ h->val;
121 h->hashval2[hpos] = h->val2;
122 if (h->head2[h->val2] != -1 && h->hashval2[h->head2[h->val2]] == h->val2) {
123 h->prev2[hpos] = h->head2[h->val2];
124 }
125 else h->prev2[hpos] = hpos;
126 h->head2[h->val2] = hpos;
127 #endif
128 }
129
ZopfliWarmupHash(const unsigned char * array,size_t pos,size_t end,ZopfliHash * h)130 void ZopfliWarmupHash(const unsigned char* array, size_t pos, size_t end,
131 ZopfliHash* h) {
132 (void)end;
133 UpdateHashValue(h, array[pos + 0]);
134 UpdateHashValue(h, array[pos + 1]);
135 }
136