NAME Mail::Message::Checksum - utilities for checksum. SYNOPSIS use Mail::Message::Checksum; $cksum = new Mail::Message::Checksum; $md5sum = $cksum->md5( \$string ); METHODS new() constructor. It checks we can use MD5 perl module or we need to use external programs such as "md5", "cksum", et.al. md5(\$string) same as md5_str_ref(). md5_str_ref(\$string) return the md5 checksum of the specified string $string. md5_file($file) return the md5 checksum of the specified file. cksum1($file) "not implemented". This is a 16-bit checksum. The algorithm used by historic BSD systems as the sum(1) algorithm and by historic AT&T System V UNIX systems as the sum algorithm when using the "-r" option. cksum2($file) return the traditional checksum of the given $file. This is a 32-bit checksum. The algorithm used by historic AT&T System V UNIX systems as the default sum algorithm. See POSIX 1003.2 for more details. crc($file) "not implemented". The default CRC used is based on the polynomial used for CRC error checking in the networking standard ISO 8802-3:1989 The CRC checksum encoding is defined by the generating polynomial: G(x) = x^32 + x^26 + x^23 + x^22 + x^16 + x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1 Mathematically, the CRC value corresponding to a given file is defined by the following procedure: The n bits to be evaluated are considered to be the coefficients of a mod 2 polynomial M(x) of degree n-1. These n bits are the bits from the file, with the most significant bit being the most signif- icant bit of the first octet of the file and the last bit being the least significant bit of the last octet, padded with zero bits (if necessary) to achieve an integral number of octets, followed by one or more octets representing the length of the file as a binary val- ue, least significant octet first. The smallest number of octets capable of representing this integer are used. M(x) is multiplied by x^32 (i.e., shifted left 32 bits) and divided by G(x) using mod 2 division, producing a remainder R(x) of degree <= 31. The coefficients of R(x) are considered to be a 32-bit sequence. The bit sequence is complemented and the result is the CRC. ACCESS METHODS set_mode($mode) set mode. get_mode() get current mode. return unknown if not set. CODING STYLE See "http://www.fml.org/software/FNF/" on fml coding style guide. AUTHOR Ken'ichi Fukamachi COPYRIGHT Copyright (C) 2001,2002,2003,2004,2005,2006 Ken'ichi Fukamachi All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. HISTORY Mail::Message::Checksum first appeared in fml8 mailing list driver package. See "http://www.fml.org/" for more details. Algorithm used here is based on NetBSD cksum library (C program).