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1 | /* |
2 | * Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de> | |
3 | * | |
4 | * This file is part of FFmpeg. | |
5 | * | |
6 | * FFmpeg is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU Lesser General Public | |
8 | * License as published by the Free Software Foundation; either | |
9 | * version 2.1 of the License, or (at your option) any later version. | |
10 | * | |
11 | * FFmpeg is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * Lesser General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU Lesser General Public | |
17 | * License along with FFmpeg; if not, write to the Free Software | |
18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
19 | */ | |
20 | #include <stdint.h> | |
21 | #include "mem.h" | |
22 | #include "intreadwrite.h" | |
23 | #include "murmur3.h" | |
24 | ||
25 | typedef struct AVMurMur3 { | |
26 | uint64_t h1, h2; | |
27 | uint8_t state[16]; | |
28 | int state_pos; | |
29 | uint64_t len; | |
30 | } AVMurMur3; | |
31 | ||
32 | AVMurMur3 *av_murmur3_alloc(void) | |
33 | { | |
34 | return av_mallocz(sizeof(AVMurMur3)); | |
35 | } | |
36 | ||
37 | void av_murmur3_init_seeded(AVMurMur3 *c, uint64_t seed) | |
38 | { | |
39 | memset(c, 0, sizeof(*c)); | |
40 | c->h1 = c->h2 = seed; | |
41 | } | |
42 | ||
43 | void av_murmur3_init(AVMurMur3 *c) | |
44 | { | |
45 | // arbitrary random number as seed | |
46 | av_murmur3_init_seeded(c, 0x725acc55daddca55); | |
47 | } | |
48 | ||
49 | static const uint64_t c1 = UINT64_C(0x87c37b91114253d5); | |
50 | static const uint64_t c2 = UINT64_C(0x4cf5ad432745937f); | |
51 | ||
52 | #define ROT(a, b) ((a << b) | (a >> (64 - b))) | |
53 | ||
54 | static uint64_t inline get_k1(const uint8_t *src) | |
55 | { | |
56 | uint64_t k = AV_RL64(src); | |
57 | k *= c1; | |
58 | k = ROT(k, 31); | |
59 | k *= c2; | |
60 | return k; | |
61 | } | |
62 | ||
63 | static uint64_t inline get_k2(const uint8_t *src) | |
64 | { | |
65 | uint64_t k = AV_RL64(src + 8); | |
66 | k *= c2; | |
67 | k = ROT(k, 33); | |
68 | k *= c1; | |
69 | return k; | |
70 | } | |
71 | ||
72 | static uint64_t inline update_h1(uint64_t k, uint64_t h1, uint64_t h2) | |
73 | { | |
74 | k ^= h1; | |
75 | k = ROT(k, 27); | |
76 | k += h2; | |
77 | k *= 5; | |
78 | k += 0x52dce729; | |
79 | return k; | |
80 | } | |
81 | ||
82 | static uint64_t inline update_h2(uint64_t k, uint64_t h1, uint64_t h2) | |
83 | { | |
84 | k ^= h2; | |
85 | k = ROT(k, 31); | |
86 | k += h1; | |
87 | k *= 5; | |
88 | k += 0x38495ab5; | |
89 | return k; | |
90 | } | |
91 | ||
92 | void av_murmur3_update(AVMurMur3 *c, const uint8_t *src, int len) | |
93 | { | |
94 | const uint8_t *end; | |
95 | uint64_t h1 = c->h1, h2 = c->h2; | |
96 | uint64_t k1, k2; | |
97 | if (len <= 0) return; | |
98 | c->len += len; | |
99 | if (c->state_pos > 0) { | |
100 | while (c->state_pos < 16) { | |
101 | c->state[c->state_pos++] = *src++; | |
102 | if (--len <= 0) return; | |
103 | } | |
104 | c->state_pos = 0; | |
105 | k1 = get_k1(c->state); | |
106 | k2 = get_k2(c->state); | |
107 | h1 = update_h1(k1, h1, h2); | |
108 | h2 = update_h2(k2, h1, h2); | |
109 | } | |
110 | ||
111 | end = src + (len & ~15); | |
112 | while (src < end) { | |
113 | // These could be done sequentially instead | |
114 | // of interleaved, but like this is over 10% faster | |
115 | k1 = get_k1(src); | |
116 | k2 = get_k2(src); | |
117 | h1 = update_h1(k1, h1, h2); | |
118 | h2 = update_h2(k2, h1, h2); | |
119 | src += 16; | |
120 | } | |
121 | c->h1 = h1; | |
122 | c->h2 = h2; | |
123 | ||
124 | len &= 15; | |
125 | if (len > 0) { | |
126 | memcpy(c->state, src, len); | |
127 | c->state_pos = len; | |
128 | } | |
129 | } | |
130 | ||
131 | static inline uint64_t fmix(uint64_t k) | |
132 | { | |
133 | k ^= k >> 33; | |
134 | k *= UINT64_C(0xff51afd7ed558ccd); | |
135 | k ^= k >> 33; | |
136 | k *= UINT64_C(0xc4ceb9fe1a85ec53); | |
137 | k ^= k >> 33; | |
138 | return k; | |
139 | } | |
140 | ||
141 | void av_murmur3_final(AVMurMur3 *c, uint8_t dst[16]) | |
142 | { | |
143 | uint64_t h1 = c->h1, h2 = c->h2; | |
144 | memset(c->state + c->state_pos, 0, sizeof(c->state) - c->state_pos); | |
145 | h1 ^= get_k1(c->state) ^ c->len; | |
146 | h2 ^= get_k2(c->state) ^ c->len; | |
147 | h1 += h2; | |
148 | h2 += h1; | |
149 | h1 = fmix(h1); | |
150 | h2 = fmix(h2); | |
151 | h1 += h2; | |
152 | h2 += h1; | |
153 | AV_WL64(dst, h1); | |
154 | AV_WL64(dst + 8, h2); | |
155 | } | |
156 | ||
157 | #ifdef TEST | |
158 | int main(void) | |
159 | { | |
160 | int i; | |
161 | uint8_t hash_result[16] = {0}; | |
162 | AVMurMur3 *ctx = av_murmur3_alloc(); | |
163 | #if 1 | |
164 | uint8_t in[256] = {0}; | |
165 | uint8_t *hashes = av_mallocz(256 * 16); | |
166 | for (i = 0; i < 256; i++) | |
167 | { | |
168 | in[i] = i; | |
169 | av_murmur3_init_seeded(ctx, 256 - i); | |
170 | // Note: this actually tests hashing 0 bytes | |
171 | av_murmur3_update(ctx, in, i); | |
172 | av_murmur3_final(ctx, hashes + 16 * i); | |
173 | } | |
174 | av_murmur3_init_seeded(ctx, 0); | |
175 | av_murmur3_update(ctx, hashes, 256 * 16); | |
176 | av_murmur3_final(ctx, hash_result); | |
177 | av_free(hashes); | |
178 | av_freep(&ctx); | |
179 | printf("result: 0x%"PRIx64" 0x%"PRIx64"\n", AV_RL64(hash_result), AV_RL64(hash_result + 8)); | |
180 | // official reference value is 32 bit | |
181 | return AV_RL32(hash_result) != 0x6384ba69; | |
182 | #else | |
183 | uint8_t *in = av_mallocz(512*1024); | |
184 | av_murmur3_init(ctx); | |
185 | for (i = 0; i < 40*1024; i++) | |
186 | av_murmur3_update(ctx, in, 512*1024); | |
187 | av_murmur3_final(ctx, hash_result); | |
188 | av_free(in); | |
189 | return hash_result[0]; | |
190 | #endif | |
191 | } | |
192 | #endif |