man crc16 () - Perform a 16bit Cyclic Redundancy Check
NAME
crc16 - Perform a 16bit Cyclic Redundancy Check
SYNOPSIS
package require Tcl 8.2 package require crc16 ?1.1? ::crc::crc16 ?-format format? ?-seed value? ?-implementation procname? message ::crc::crc16 ?-format format? ?-seed value? ?-implementation procname? -filename file ::crc::crc-ccitt ?-format format? ?-seed value? ?-implementation procname? message ::crc::crc-ccitt ?-format format? ?-seed value? ?-implementation procname? -filename file
DESCRIPTION
This package provides a Tcl-only implementation of the CRC algorithms based upon information provided at http://www.microconsultants.com/tips/crc/crc.txt There are a number of permutations available for calculating CRC checksums and this package can handle all of them. Defaults are set up for the most common cases.
COMMANDS
- ::crc::crc16 ?-format format? ?-seed value? ?-implementation procname? message
- ::crc::crc16 ?-format format? ?-seed value? ?-implementation procname? -filename file
- ::crc::crc-ccitt ?-format format? ?-seed value? ?-implementation procname? message
- ::crc::crc-ccitt ?-format format? ?-seed value? ?-implementation procname? -filename file
- The command takes string data or a file name and returns a checksum value calculated using the CRC algorithm. The command used sets up the CRC polynomial, initial value and bit ordering for the desired standard checksum calculation. The result is formatted using the format(n) specifier provided or as an unsigned integer (%u) by default.
OPTIONS
- -filename name
- Return a checksum for the file contents instead of for parameter data.
- -format string
- Return the checksum using an alternative format template.
- -seed value
- Select an alternative seed value for the CRC calculation. The default is 0 for the CRC16 calculation and 0xFFFF for the CCITT version. This can be useful for calculating the CRC for data structures without first converting the whole structure into a string. The CRC of the previous member can be used as the seed for calculating the CRC of the next member. It is also used for accumulating a checksum from fragments of a large message (or file)
- -implementation procname
- This hook is provided to allow users to provide their own implementation (perhaps a C compiled extension). The procedure specfied is called with two parameters. The first is the data to be checksummed and the second is the seed value. An integer is expected as the result.
EXAMPLES
% crc::crc16 "Hello, World!" 64077
% crc::crc-ccitt "Hello, World!" 26586
% crc::crc16 -format 0x%X "Hello, World!" 0xFA4D
% crc::crc16 -file crc16.tcl 51675
AUTHORS
Pat Thoyts
SEE ALSO
KEYWORDS
checksum, cksum, crc, crc16, crc32, cyclic redundancy check, data integrity, security
COPYRIGHT
Copyright (c) 2002, Pat Thoyts