cksum(n)                   Cyclic Redundancy Checks                   cksum(n)



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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

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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(n) 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(n), sum(n)

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(n)
