crc32(n)						  Cyclic Redundancy Check (crc32)						  crc32(n)

NAME

       crc32 - Perform a 32bit Cyclic Redundancy Check

SYNOPSIS

       package require Tcl 8.2

       package require crc32 ?1.0?

       ::crc::crc32 ?-format format? ?-seed value? ?-implementation procname? message

       ::crc::crc32 ?-format format? ?-seed value? ?-implementation procname? -filename file

DESCRIPTION

       This  package  provides	a  Tcl-only  implementation of the CRC-32 algorithm based upon information provided at http://www.naaccr.org/stan-
       dard/crc32/document.html If the Trf package is available then the crc-zlib command is used to perform the calculation.

COMMANDS

       ::crc::crc32 ?-format format? ?-seed value? ?-implementation procname? message

       ::crc::crc32 ?-format format? ?-seed value? ?-implementation procname? -filename file
	      The command takes string data or a file name and returns a checksum value calculated using the CRC-32 algorithm. The result is  for-
	      matted using the format(n) specifier provided or as an unsigned integer (%u) by default.

OPTIONS

       -filename name
	      Return a checksum for the file contents instead of for parameter data.

       -format string
	      Return the checksum using an alternative format template.

       -seed value
	      Select  an alternative seed value for the CRC calculation. The default is 0xffffffff. This can be useful for calculating the CRC for
	      data structures without first converting the whole structure into a string. The CRC of the previous member can be used as  the  seed
	      for calculating the CRC of the next member.

	      Note  that as the Trf command crc-zlib cannot accept a seed value, use of this option will force the use of the Tcl only implementa-
	      tion.

       -implementation procname
	      This hook is provided to allow users to provide their own implementation (perhaps a C compiled extension) or to  explicitly  request
	      use  of  the  Tcl  only  implementation  when Trf is installed (by setting -implementation crc::Crc32_tcl. The procedure specfied is
	      called with two parameters. The first is the data to be checksummed and the second is the seed value. A 32bit integer is expected as
	      the result.

EXAMPLES

       % crc::crc32 "Hello, World!"
       3964322768

       % crc::crc32 -format 0x%X "Hello, World!"
       0xEC4AC3D0

       % crc::crc32 -file crc32.tcl
       483919716

SEE ALSO

       sum(n), cksum(n)

AUTHORS

       Pat Thoyts

KEYWORDS

       cksum, checksum, crc, crc32, cyclic redundancy check, data integrity, security

crc									1.0								  crc32(n)