/* * 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); }