


cksum(n)             Cyclic Redundancy Checks            cksum(n)


______________________________________________________________________________

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) algo-
              rithm. 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



crc                           1.1.3                             1





cksum(n)             Cyclic Redundancy Checks            cksum(n)


       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  CksumUp-
              date  $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.



crc                           1.1.3                             2





cksum(n)             Cyclic Redundancy Checks            cksum(n)


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                             3


