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/*
* This file is part of LibCSS
* Licensed under the MIT License,
* http://www.opensource.org/licenses/mit-license.php
*
* Copyright 2015 Michael Drake <tlsa@netsurf-browser.org>
*/
#ifndef css_select_arena_hash_h_
#define css_select_arena_hash_h_
#include <stdint.h>
/**
* Currently 32-bit MurmurHash2.
*
* Created by Austin Appleby, and placed in the public domain.
* https://sites.google.com/site/murmurhash/
*
* Refactored and adapted a little for libcss.
*/
static inline uint32_t css__arena_hash(const uint8_t *data, size_t len)
{
/* Hashing constants */
const uint32_t m = 0x5bd1e995;
const int r = 24;
/* Start with length */
uint32_t h = len;
/* Hash four bytes at a time */
while (len >= 4) {
/* If we could ensure 4-byte alignment of the input, this
* could be faster. */
uint32_t k =
(((uint32_t) data[0]) ) |
(((uint32_t) data[1]) << 8) |
(((uint32_t) data[2]) << 16) |
(((uint32_t) data[3]) << 24);
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
/* Hash any left over bytes */
switch (len) {
case 3: h ^= data[2] << 16;
case 2: h ^= data[1] << 8;
case 1: h ^= data[0];
h *= m;
}
/* Finalise */
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
#endif
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