From 00c0d78199fcfbbb20828be5e06fd2d271fa4c1e Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Sun, 24 Mar 2024 23:49:26 +0100
Subject: Initial commit

---
 deimos/core/hash.h | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 deimos/core/hash.h

(limited to 'deimos/core/hash.h')

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
+
-- 
cgit