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use fnv-1a hashing instead of djb2

master
Daniel Kolesa 2015-07-20 02:20:35 +01:00
parent a048a5384c
commit cc0fccb8cf
1 changed files with 17 additions and 2 deletions
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19
ostd/functional.hh
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@ -218,10 +218,25 @@ OSTD_HASH_BASIC(Wchar)
#undef OSTD_HASH_BASIC
namespace detail {
template<Size E> struct FnvConstants {
static constexpr Size prime = 16777619u;
static constexpr Size offset = 2166136261u;
};
template<> struct FnvConstants<8> {
static constexpr Size prime = 1099511628211u;
static constexpr Size offset = 14695981039346656037u;
};
inline Size mem_hash(const void *p, Size l) {
using Consts = FnvConstants<sizeof(Size)>;
const byte *d = (const byte *)p;
Size h = 5381;
for (Size i = 0; i < l; ++i) h = ((h << 5) + h) ^ d[i];
Size h = Consts::offset;
for (const byte *it = d, *end = d + l; it != end; ++it) {
h ^= *it;
h *= Consts::prime;
}
return h;
}