diff options
| author | Steven Le Rouzic <steven.lerouzic@gmail.com> | 2024-03-24 23:49:26 +0100 |
|---|---|---|
| committer | Steven Le Rouzic <steven.lerouzic@gmail.com> | 2024-03-24 23:49:26 +0100 |
| commit | 00c0d78199fcfbbb20828be5e06fd2d271fa4c1e (patch) | |
| tree | e74aa52990af33f7bf1e4d452b464c3e24d1017e /deimos/core/hash.h | |
Initial commit
Diffstat (limited to 'deimos/core/hash.h')
| -rw-r--r-- | deimos/core/hash.h | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/deimos/core/hash.h b/deimos/core/hash.h new file mode 100644 index 0000000..3f8935c --- /dev/null +++ b/deimos/core/hash.h @@ -0,0 +1,110 @@ +#pragma once
+
+#include "deimos/core/base.h"
+
+namespace deimos
+{
+
+constexpr uint64 MurmurHash3_GetBlock64(const char* key, uint64 block)
+{
+ // NOLINTBEGIN
+ key += block * 8;
+ return
+ (uint64)((uint8)key[0])
+ | ((uint64)((uint8)key[1]) << 8)
+ | ((uint64)((uint8)key[2]) << 16)
+ | ((uint64)((uint8)key[3]) << 24)
+ | ((uint64)((uint8)key[4]) << 32)
+ | ((uint64)((uint8)key[5]) << 40)
+ | ((uint64)((uint8)key[6]) << 48)
+ | ((uint64)((uint8)key[7]) << 56);
+ // NOLINTEND
+}
+
+constexpr uint64 MurmurHash3_Fmix64(uint64 k)
+{
+ k ^= k >> 33U;
+ k *= 0xff51afd7ed558ccdULL;
+ k ^= k >> 33U;
+ k *= 0xc4ceb9fe1a85ec53ULL;
+ k ^= k >> 33U;
+ return k;
+}
+
+constexpr uint128 MurmurHash3_x64_128(const char* key)
+{
+ // NOLINTBEGIN
+ const uint64 len = __builtin_strlen(key);
+ const uint64 nblocks = len / 16;
+
+ const int64 seed = 0;
+ uint64 h1 = seed;
+ uint64 h2 = seed;
+
+ const uint64 c1 = 0x87c37b91114253d5ULL;
+ const uint64 c2 = 0x4cf5ad432745937fULL;
+
+ //----------
+ // body
+
+ for(uint64 i = 0; i < nblocks; i++)
+ {
+ uint64 k1 = MurmurHash3_GetBlock64(key, i * 2 + 0);
+ uint64 k2 = MurmurHash3_GetBlock64(key, i * 2 + 1);
+
+ k1 *= c1; k1 = _rotl64(k1, 31); k1 *= c2; h1 ^= k1;
+ h1 = _rotl64(h1, 27); h1 += h2; h1 = h1*5+0x52dce729;
+ k2 *= c2; k2 = _rotl64(k2, 33); k2 *= c1; h2 ^= k2;
+ h2 = _rotl64(h2, 31); h2 += h1; h2 = h2*5+0x38495ab5;
+ }
+
+ //----------
+ // tail
+
+ const char* tail = key + nblocks * 16;
+
+ uint64 k1 = 0;
+ uint64 k2 = 0;
+
+ switch (len & 15ULL)
+ {
+ case 15: k2 ^= ((uint64)(uint8)tail[14]) << 48U;
+ case 14: k2 ^= ((uint64)(uint8)tail[13]) << 40U;
+ case 13: k2 ^= ((uint64)(uint8)tail[12]) << 32U;
+ case 12: k2 ^= ((uint64)(uint8)tail[11]) << 24U;
+ case 11: k2 ^= ((uint64)(uint8)tail[10]) << 16U;
+ case 10: k2 ^= ((uint64)(uint8)tail[ 9]) << 8U;
+ case 9: k2 ^= ((uint64)(uint8)tail[ 8]) << 0U;
+ k2 *= c2; k2 = _rotl64(k2,33); k2 *= c1; h2 ^= k2;
+
+ case 8: k1 ^= ((uint64)(uint8)tail[ 7]) << 56U;
+ case 7: k1 ^= ((uint64)(uint8)tail[ 6]) << 48U;
+ case 6: k1 ^= ((uint64)(uint8)tail[ 5]) << 40U;
+ case 5: k1 ^= ((uint64)(uint8)tail[ 4]) << 32U;
+ case 4: k1 ^= ((uint64)(uint8)tail[ 3]) << 24U;
+ case 3: k1 ^= ((uint64)(uint8)tail[ 2]) << 16U;
+ case 2: k1 ^= ((uint64)(uint8)tail[ 1]) << 8U;
+ case 1: k1 ^= ((uint64)(uint8)tail[ 0]) << 0U;
+ k1 *= c1; k1 = _rotl64(k1,31); k1 *= c2; h1 ^= k1;
+ };
+
+ //----------
+ // finalization
+
+ h1 ^= len; h2 ^= len;
+
+ h1 += h2;
+ h2 += h1;
+
+ h1 = MurmurHash3_Fmix64(h1);
+ h2 = MurmurHash3_Fmix64(h2);
+
+ h1 += h2;
+ h2 += h1;
+ // NOLINTEND
+
+ return uint128{h1, h2};
+}
+
+} // namespace deimos
+
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