cksum(3tcl) Cyclic Redundancy Checks cksum(3tcl)______________________________________________________________________________NAMEcksum - 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(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 use‐
ful 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.
SEE ALSOcrc32(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
crc 1.1.3 cksum(3tcl)
