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