/ 
String-CRC32C-1.0
/ String::CRC32C

NAME

String::CRC32C - Castagnoli CRC

SYNOPSIS

use String::CRC32C; # does not export anything by default
use String::CRC32C 'crc32c';

$crc = crc32 "some string";
$crc = crc32 "some string", $initvalue;

DESCRIPTION

This module calculates the Castagnoli CRC32 variant (polynomial 0x11EDC6F41).

It is used by iSCSI, SCTP, BTRFS, ext4, leveldb, x86 CPUs and others.

This module uses an optimized implementation for SSE 4.2 targets (GCC and compatible supported, SSE 4.2 must be enabled in your Perl) and the SlicingBy8 algorithm for anything else.

$crc32c = crc32c $string[, $initvalue]

Calculates the CRC32C value of the given $string and returns it as a 32 bit unsigned integer.

To get the common hex form, use one of:

sprintf "%08x", crc32c $string
unpack "H*", pack "L>", crc32c $string

A seed/initial crc value can be given as second argument. Note that both the initial value and the result value are inverted (pre-inversion and post-inversion), e.g. a common init value of -1 from other descriptions needs to be given as 0 (or ~-1).

This allows easy chaining, e.g.

(crc32c "abcdefghi") eq (crc32 "ghi", crc32 "def", crc32 "abc")
$String::CRC32C::IMPL

Contains a string indicating the implementation that will be used. Currently either SlicingBy8 for the portable implementation or IntelCSSE42 for the SSE 4.2 optimized intel version.

PERLMULTICORE SUPPORT

This module supports the perl multicore spoecification (http://perlmulticore.schmorp.de/): the crc32c function will relinquish the current thread for crc32c lengths larger than 64k (the break-even point on my machine is around 128k), so multiprocessing makes only sense for very long blocks.

AUTHOR

Marc Lehmann <schmorp@schmorp.de>
http://home.schmorp.de/

CRC32C code by various sources, ported from https://github.com/htot/crc32c, see sources for details.