NAME

Digest::xxHash - xxHash Implementation For Perl

SYNOPSIS

    use Digest::xxHash qw[xxhash xxhash_hex];

    my $hash = xxhash( $data, $seed );
    my $hex  = xxhash_hex( $data, $seed );
    
    # OO remix!
    
    my $digest = Digest::xxHash->new( $seed );
    $digest->add( $data );
    $digest->add( $more_data );
    my $xxhash = $digest->digest( );
    my $xxhex  = $digest->digest_hex( );

DESCRIPTION

This module provides both a functional and an OO interface to xxHash functions. xxHash is an extremely fast (and likely very weak) algorithm that claims to work at speeds close to RAM limits.

FUNCTIONAL INTERFACE

These functions are easy to use but aren't very flexible.

$h = xxhash( $data, $seed )

Calculates a 32 bit hash.

$h = xxhash_hex( $data, $seed )

Calculates a 32 bit hash and returns it as a hex string.

OO INTERFACE

The OO interface is a lot more flexible but less succinct.

$d = Digest::xxHash->new( $seed )

Returns a new Digest::xxHash object. This is a simple constructor.

$d->add( $data )

Adds data to the spool that will eventually be hashed. You may call this as many times as needed.

$d->reset( )

This will reset the data added to the object. This is great if you want to hash several pieces of data with the same seed.

$h = $d->digest( )

Calculates a 32 bit hash of the data added to the object.

$h = $d->digest_hex( )

Calculates a 32 bit hash of the data added to the object and returns it as a hex string.

SPEED

The strength of xxHash isn't very well documented but it's fast. According to the xxhash project's website, when run in a single thread on a 32bit Windows 7 box with a 3GHz Core 2 Duo processor, xxhash looks a little like:

    Name            Speed       Q.Score   Author
    xxHash          5.4 GB/s     10
    MumurHash 3a    2.7 GB/s     10       Austin Appleby
    SpookyHash      2.0 GB/s     10       Bob Jenkins
    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. Hash functions with a Q.score < 5 are not listed in this table.

LICENSE

xxxHash is covered by the BSD license.

I don't actually care about the wrapper I've written.

AUTHOR

Sanko Robinson <sanko@cpan.org>

xxHash by Yann Collet.

cpanm Digest::xxHash

perl -MCPAN -e shell
install Digest::xxHash