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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  ?1.1.2?

       ::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  calcu-lated calculated
              lated using the cksum(1) algorithm. The result is formatted using the format(n) specifier pro-vided provided
              vided 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  chan-nel channel
              nel  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 han-dler handler
       dler 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://source-
       forge.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

COPYRIGHT
       Copyright (c) 2002, Pat Thoyts




crc                                                 1.1.2                                           cksum(n)