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/**
* Compiler implementation of the D programming language
* http://dlang.org
*
* Copyright: Copyright (C) 1999-2020 by The D Language Foundation, All Rights Reserved
* Authors: Martin Nowak, Walter Bright, http://www.digitalmars.com
* License: $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
* Source: $(DMDSRC root/_hash.h)
*/
#pragma once
#include "dsystem.h" // uint{8|16|32}_t
// MurmurHash2 was written by Austin Appleby, and is placed in the public
// domain. The author hereby disclaims copyright to this source code.
// https://sites.google.com/site/murmurhash/
static inline uint32_t calcHash(const uint8_t *data, size_t len)
{
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
const uint32_t m = 0x5bd1e995;
const int r = 24;
// Initialize the hash to a 'random' value
uint32_t h = (uint32_t)len;
// Mix 4 bytes at a time into the hash
while(len >= 4)
{
uint32_t k = data[3] << 24 | data[2] << 16 | data[1] << 8 | data[0];
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
// Handle the last few bytes of the input array
switch(len & 3)
{
case 3: h ^= data[2] << 16; /* fall through */
case 2: h ^= data[1] << 8; /* fall through */
case 1: h ^= data[0];
h *= m;
}
// Do a few final mixes of the hash to ensure the last few
// bytes are well-incorporated.
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
static inline uint32_t calcHash(const char *data, size_t len)
{
return calcHash((const uint8_t *)data, len);
}
// combine and mix two words (boost::hash_combine)
static inline size_t mixHash(size_t h, size_t k)
{
return h ^ (k + 0x9e3779b9 + (h << 6) + (h >> 2));
}
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