Module fasthash::xx

xxHash - Extremely fast hash algorithm

by Yann Collet

http://cyan4973.github.io/xxHash/

xxHash is an Extremely fast Hash algorithm, running at RAM speed limits. It successfully completes the SMHasher test suite which evaluates collision, dispersion and randomness qualities of hash functions. Code is highly portable, and hashes are identical on all platforms (little / big endian).

Benchmarks

The benchmark uses SMHasher speed test, compiled with Visual 2010 on a Windows Seven 32-bits box. The reference system uses a Core 2 Duo @3GHz

Name	Speed	Quality	Author
xxHash	5.4 GB/s	10	Y.C.
MurmurHash 3a	2.7 GB/s	10	Austin Appleby
SBox	1.4 GB/s	9	Bret Mulvey
Lookup3	1.2 GB/s	9	Bob Jenkins
CityHash64	1.05 GB/s	10	Pike & Alakuijala
FNV	0.55 GB/s	5	Fowler, Noll, Vo
CRC32	0.43 GB/s	9
MD5-32	0.33 GB/s	10	Ronald L.Rivest
SHA1-32	0.28 GB/s	10

Q.Score is a measure of quality of the hash function. It depends on successfully passing SMHasher test set. 10 is a perfect score. Algorithms with a score < 5 are not listed on this table.

A new version, XXH64, has been created thanks to Mathias Westerdahl's contribution, which offers superior speed and dispersion for 64-bits systems. Note however that 32-bits applications will still run faster using the 32-bits version.

SMHasher speed test, compiled using GCC 4.8.2, on Linux Mint 64-bits. The reference system uses a Core i5-3340M @2.7GHz

Version	Speed on 64-bits	Speed on 32-bits
XXH64	13.8 GB/s	1.9 GB/s
XXH32	6.8 GB/s	6.0 GB/s

This project also includes a command line utility, named xxhsum, offering similar features as md5sum, thanks to Takayuki Matsuoka contributions.

Example

use std::hash::{Hash, Hasher};

use fasthash::{xx, XXHasher};

fn hash<T: Hash>(t: &T) -> u64 {
    let mut s: XXHasher = Default::default();
    t.hash(&mut s);
    s.finish()
}

let h = xx::hash64(b"hello world\xff");

assert_eq!(h, hash(&"hello world"));

Structs

XXHash32	xxHash 32-bit hash functions
XXHash64	xxHash 64-bit hash functions
XXHasher32	An implementation of std::hash::Hasher.
XXHasher64	An implementation of std::hash::Hasher.

Functions

hash32	xxHash 32-bit hash functions for a byte array.
hash32_with_seed	xxHash 32-bit hash function for a byte array. For convenience, a 32-bit seed is also hashed into the result.
hash64	xxHash 64-bit hash functions for a byte array.
hash64_with_seed	xxHash 64-bit hash function for a byte array. For convenience, a 64-bit seed is also hashed into the result.