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/*
* Copyright (C) 2013 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdint.h>
#include "mem.h"
#include "intreadwrite.h"
#include "murmur3.h"
typedef struct AVMurMur3 {
uint64_t h1, h2;
uint8_t state[16];
int state_pos;
uint64_t len;
} AVMurMur3;
AVMurMur3 *av_murmur3_alloc(void)
{
return av_mallocz(sizeof(AVMurMur3));
}
void av_murmur3_init_seeded(AVMurMur3 *c, uint64_t seed)
{
memset(c, 0, sizeof(*c));
c->h1 = c->h2 = seed;
}
void av_murmur3_init(AVMurMur3 *c)
{
// arbitrary random number as seed
av_murmur3_init_seeded(c, 0x725acc55daddca55);
}
static const uint64_t c1 = UINT64_C(0x87c37b91114253d5);
static const uint64_t c2 = UINT64_C(0x4cf5ad432745937f);
#define ROT(a, b) ((a << b) | (a >> (64 - b)))
static uint64_t inline get_k1(const uint8_t *src)
{
uint64_t k = AV_RL64(src);
k *= c1;
k = ROT(k, 31);
k *= c2;
return k;
}
static uint64_t inline get_k2(const uint8_t *src)
{
uint64_t k = AV_RL64(src + 8);
k *= c2;
k = ROT(k, 33);
k *= c1;
return k;
}
static uint64_t inline update_h1(uint64_t k, uint64_t h1, uint64_t h2)
{
k ^= h1;
k = ROT(k, 27);
k += h2;
k *= 5;
k += 0x52dce729;
return k;
}
static uint64_t inline update_h2(uint64_t k, uint64_t h1, uint64_t h2)
{
k ^= h2;
k = ROT(k, 31);
k += h1;
k *= 5;
k += 0x38495ab5;
return k;
}
void av_murmur3_update(AVMurMur3 *c, const uint8_t *src, int len)
{
const uint8_t *end;
uint64_t h1 = c->h1, h2 = c->h2;
uint64_t k1, k2;
if (len <= 0) return;
c->len += len;
if (c->state_pos > 0) {
while (c->state_pos < 16) {
c->state[c->state_pos++] = *src++;
if (--len <= 0) return;
}
c->state_pos = 0;
k1 = get_k1(c->state);
k2 = get_k2(c->state);
h1 = update_h1(k1, h1, h2);
h2 = update_h2(k2, h1, h2);
}
end = src + (len & ~15);
while (src < end) {
// These could be done sequentially instead
// of interleaved, but like this is over 10% faster
k1 = get_k1(src);
k2 = get_k2(src);
h1 = update_h1(k1, h1, h2);
h2 = update_h2(k2, h1, h2);
src += 16;
}
c->h1 = h1;
c->h2 = h2;
len &= 15;
if (len > 0) {
memcpy(c->state, src, len);
c->state_pos = len;
}
}
static inline uint64_t fmix(uint64_t k)
{
k ^= k >> 33;
k *= UINT64_C(0xff51afd7ed558ccd);
k ^= k >> 33;
k *= UINT64_C(0xc4ceb9fe1a85ec53);
k ^= k >> 33;
return k;
}
void av_murmur3_final(AVMurMur3 *c, uint8_t dst[16])
{
uint64_t h1 = c->h1, h2 = c->h2;
memset(c->state + c->state_pos, 0, sizeof(c->state) - c->state_pos);
h1 ^= get_k1(c->state) ^ c->len;
h2 ^= get_k2(c->state) ^ c->len;
h1 += h2;
h2 += h1;
h1 = fmix(h1);
h2 = fmix(h2);
h1 += h2;
h2 += h1;
AV_WL64(dst, h1);
AV_WL64(dst + 8, h2);
}
#ifdef TEST
int main(void)
{
int i;
uint8_t hash_result[16] = {0};
AVMurMur3 *ctx = av_murmur3_alloc();
#if 1
uint8_t in[256] = {0};
uint8_t *hashes = av_mallocz(256 * 16);
for (i = 0; i < 256; i++)
{
in[i] = i;
av_murmur3_init_seeded(ctx, 256 - i);
// Note: this actually tests hashing 0 bytes
av_murmur3_update(ctx, in, i);
av_murmur3_final(ctx, hashes + 16 * i);
}
av_murmur3_init_seeded(ctx, 0);
av_murmur3_update(ctx, hashes, 256 * 16);
av_murmur3_final(ctx, hash_result);
av_free(hashes);
printf("result: 0x%"PRIx64" 0x%"PRIx64"\n", AV_RL64(hash_result), AV_RL64(hash_result + 8));
// official reference value is 32 bit
return AV_RL32(hash_result) != 0x6384ba69;
#else
uint8_t *in = av_mallocz(512*1024);
av_murmur3_init(ctx);
for (i = 0; i < 40*1024; i++)
av_murmur3_update(ctx, in, 512*1024);
av_murmur3_final(ctx, hash_result);
av_free(in);
return hash_result[0];
#endif
}
#endif
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