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This is a C version of Bob Jenkin's spooky hash. The only advantage over Bob's original version is that it is in C, not C++ and comes with some test and benchmark code. This is a very competitive hash function, but is somewhat unportable (64bit little endian only). It's more portable than some of the contenders like CityHash. Quoting Bobs original description: // 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. // // 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 some platforms. 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.