cksum(3tcl)						     Cyclic Redundancy Checks						       cksum(3tcl)

__________________________________________________________________________________________________________________________________________________

NAME

       cksum - Calculate a cksum(1) compatible checksum

SYNOPSIS

       package require Tcl  8.2

       package require cksum  ?1.1.3?

       ::crc::cksum ?-format format? ?-chunksize size? [ -channel chan | -filename file | string ]

       ::crc::CksumInit

       ::crc::CksumUpdate token data

       ::crc::CksumFinal token

_________________________________________________________________

DESCRIPTION

       This  package  provides a Tcl implementation of the cksum(1) algorithm based upon information provided at in the GNU implementation of this
       program as part of the GNU Textutils 2.0 package.

COMMANDS

       ::crc::cksum ?-format format? ?-chunksize size? [ -channel chan | -filename file | string ]
	      The command takes string data or a channel or file name and returns a checksum value calculated using the  cksum(1)  algorithm.  The
	      result is formatted using the format(3tcl) specifier provided or as an unsigned integer (%u) by default.

OPTIONS

       -channel name
	      Return  a  checksum for the data read from a channel. The command will read data from the channel until the eof is true. If you need
	      to be able to process events during this calculation see the PROGRAMMING INTERFACE section

       -filename name
	      This is a convenience option that opens the specified file, sets the encoding to binary and then acts as if the -channel option  had
	      been used. The file is closed on completion.

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

PROGRAMMING INTERFACE

       The  cksum  package  implements the checksum using a context variable to which additional data can be added at any time. This is expecially
       useful in an event based environment such as a Tk application or a web server package. Data to be checksummed may be handled  incrementally
       during a fileevent handler in discrete chunks. This can improve the interactive nature of a GUI application and can help to avoid excessive
       memory consumption.

       ::crc::CksumInit
	      Begins a new cksum context. Returns a token ID that must be used for the remaining functions. An optional seed may be  specified	if
	      required.

       ::crc::CksumUpdate token data
	      Add  data  to  the  checksum identified by token. Calling CksumUpdate $token "abcd" is equivalent to calling CksumUpdate $token "ab"
	      followed by CksumUpdate $token "cb". See EXAMPLES.

       ::crc::CksumFinal token
	      Returns the checksum value and releases any resources held by this token. Once this command completes the token will be invalid. The
	      result is a 32 bit integer value.

EXAMPLES

	      % crc::cksum "Hello, World!"
	      2609532967

	      % crc::cksum -format 0x%X "Hello, World!"
	      0x9B8A5027

	      % crc::cksum -file cksum.tcl
	      1828321145

	      % set tok [crc::CksumInit]
	      % crc::CksumUpdate $tok "Hello, "
	      % crc::CksumUpdate $tok "World!"
	      % crc::CksumFinal $tok
	      2609532967

AUTHORS

       Pat Thoyts

BUGS, IDEAS, FEEDBACK
       This  document,	and the package it describes, will undoubtedly contain bugs and other problems.  Please report such in the category crc of
       the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas for enhancements you  may  have  for
       either package and/or documentation.

SEE ALSO

       crc32(3tcl), sum(3tcl)

KEYWORDS

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

CATEGORY

       Hashes, checksums, and encryption

COPYRIGHT

       Copyright (c) 2002, Pat Thoyts

crc								       1.1.3							       cksum(3tcl)