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) 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.
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