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cksum(n) Cyclic Redundancy Checks cksum(n) 





NAME


cksum - Calculate a cksum(1) compatible checksum






SYNOPSIS


package require Tcl 8.2


package require cksum ?1.1.4?


::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(n) specifier provided or as an
      unsigned integer (%u) by default.








OPTIONS



  

  
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

  

  
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.

  

  
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 Trackers
    [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.


When proposing code changes, please provide unified diffs,
    i.e the output of diff -u.


Note further that attachments are strongly preferred over
    inlined patches. Attachments can be made by going to the Edit form of
    the ticket immediately after its creation, and then using the left-most
    button in the secondary navigation bar.






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








  

    1.1.4
    tcllib