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(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 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(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