48 lines
1.9 KiB
C++
48 lines
1.9 KiB
C++
//
|
|
// SpookyHash: a 128-bit noncryptographic hash function
|
|
// By Bob Jenkins, public domain
|
|
// Oct 31 2010: alpha, framework + SpookyHash::Mix appears right
|
|
// Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right
|
|
// Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas
|
|
// Feb 2 2012: production, same bits as beta
|
|
// Feb 5 2012: adjusted definitions of uint* to be more portable
|
|
// Mar 30 2012: 3 bytes/cycle, not 4. Alpha was 4 but wasn't thorough enough.
|
|
// August 5 2012: SpookyV2 (different results)
|
|
//
|
|
// Up to 3 bytes/cycle for long messages. Reasonably fast for short messages.
|
|
// All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit.
|
|
//
|
|
// This was developed for and tested on 64-bit x86-compatible processors.
|
|
// It assumes the processor is little-endian. There is a macro
|
|
// controlling whether unaligned reads are allowed (by default they are).
|
|
// This should be an equally good hash on big-endian machines, but it will
|
|
// compute different results on them than on little-endian machines.
|
|
//
|
|
// Google's CityHash has similar specs to SpookyHash, and CityHash is faster
|
|
// on new Intel boxes. MD4 and MD5 also have similar specs, but they are orders
|
|
// of magnitude slower. CRCs are two or more times slower, but unlike
|
|
// SpookyHash, they have nice math for combining the CRCs of pieces to form
|
|
// the CRCs of wholes. There are also cryptographic hashes, but those are even
|
|
// slower than MD5.
|
|
//
|
|
|
|
#include <stddef.h>
|
|
#include <cstdint>
|
|
#include <utility>
|
|
|
|
class SpookyHash
|
|
{
|
|
public:
|
|
//
|
|
// SpookyHash: hash a single message in one call, produce 128-bit output
|
|
//
|
|
static void Hash128(
|
|
const void *message, // message to hash
|
|
size_t length, // length of message in bytes
|
|
uint64_t *hash1, // input seed0, output hash0
|
|
uint64_t *hash2); // input seed1, output hash1
|
|
};
|
|
|
|
|
|
|