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+/*
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+#define ROT(a, b) ((a << b) | (a >> (64 - b)))
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+
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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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+
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+static uint64_t inline 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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+
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+static uint64_t inline 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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+
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+static uint64_t inline 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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+
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+void av_murmur3_update(AVMurMur3 *c, const uint8_t *src, int len)
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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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+
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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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+
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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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+
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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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+
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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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+
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+#ifdef TEST
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+int main(void)
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+{
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+ int i;
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+ uint8_t hash_result[16] = {0};
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+ AVMurMur3 *ctx = av_murmur3_alloc();
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+#if 1
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+ uint8_t in[256] = {0};
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+ uint8_t *hashes = av_mallocz(256 * 16);
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+ for (i = 0; i < 256; i++)
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+ {
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+ in[i] = i;
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+ av_murmur3_init_seeded(ctx, 256 - i);
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+ // Note: this actually tests hashing 0 bytes
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+ av_murmur3_update(ctx, in, i);
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+ av_murmur3_final(ctx, hashes + 16 * i);
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+ }
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+ av_murmur3_init_seeded(ctx, 0);
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+ av_murmur3_update(ctx, hashes, 256 * 16);
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+ av_murmur3_final(ctx, hash_result);
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+ av_free(hashes);
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+ printf("result: 0x%"PRIx64" 0x%"PRIx64"\n", AV_RL64(hash_result), AV_RL64(hash_result + 8));
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+ // official reference value is 32 bit
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+ return AV_RL32(hash_result) != 0x6384ba69;
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+#else
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+ uint8_t *in = av_mallocz(512*1024);
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+ av_murmur3_init(ctx);
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+ for (i = 0; i < 40*1024; i++)
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+ av_murmur3_update(ctx, in, 512*1024);
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+ av_murmur3_final(ctx, hash_result);
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+ av_free(in);
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+ return hash_result[0];
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+#endif
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+}
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+#endif
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Reimar Döffinger