mirror of https://github.com/svaarala/duktape.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
58 lines
1.4 KiB
58 lines
1.4 KiB
/*
|
|
* Hash function duk_util_hashbytes().
|
|
*
|
|
* Currently, 32-bit MurmurHash2.
|
|
*
|
|
* Don't rely on specific hash values; hash function may be endianness
|
|
* dependent, for instance.
|
|
*/
|
|
|
|
#include "duk_internal.h"
|
|
|
|
#if defined(DUK_USE_STRHASH_DENSE)
|
|
/* 'magic' constants for Murmurhash2 */
|
|
#define DUK__MAGIC_M ((duk_uint32_t) 0x5bd1e995UL)
|
|
#define DUK__MAGIC_R 24
|
|
|
|
DUK_INTERNAL duk_uint32_t duk_util_hashbytes(const duk_uint8_t *data, duk_size_t len, duk_uint32_t seed) {
|
|
duk_uint32_t h = seed ^ ((duk_uint32_t) len);
|
|
|
|
while (len >= 4) {
|
|
/* Portability workaround is required for platforms without
|
|
* unaligned access. The replacement code emulates little
|
|
* endian access even on big endian architectures, which is
|
|
* OK as long as it is consistent for a build.
|
|
*/
|
|
#if defined(DUK_USE_HASHBYTES_UNALIGNED_U32_ACCESS)
|
|
duk_uint32_t k = *((const duk_uint32_t *) (const void *) data);
|
|
#else
|
|
duk_uint32_t k = ((duk_uint32_t) data[0]) | (((duk_uint32_t) data[1]) << 8) | (((duk_uint32_t) data[2]) << 16) |
|
|
(((duk_uint32_t) data[3]) << 24);
|
|
#endif
|
|
|
|
k *= DUK__MAGIC_M;
|
|
k ^= k >> DUK__MAGIC_R;
|
|
k *= DUK__MAGIC_M;
|
|
h *= DUK__MAGIC_M;
|
|
h ^= k;
|
|
data += 4;
|
|
len -= 4;
|
|
}
|
|
|
|
switch (len) {
|
|
case 3:
|
|
h ^= data[2] << 16;
|
|
case 2:
|
|
h ^= data[1] << 8;
|
|
case 1:
|
|
h ^= data[0];
|
|
h *= DUK__MAGIC_M;
|
|
}
|
|
|
|
h ^= h >> 13;
|
|
h *= DUK__MAGIC_M;
|
|
h ^= h >> 15;
|
|
|
|
return h;
|
|
}
|
|
#endif /* DUK_USE_STRHASH_DENSE */
|
|
|