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ActiveTcl User Guide
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crc16(n) 1.0.1 "Cyclic Redundancy Check (crc16)"
crc16 - Perform a 16bit Cyclic Redundancy Check
package require Tcl 8.2
package require crc16 ?1.0.1?
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.
- ::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.
- -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.
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% crc::crc16 "Hello, World!"
64077
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% crc::crc-ccitt "Hello, World!"
26586
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% crc::crc16 -format 0x%X "Hello, World!"
0xFA4D
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% crc::crc16 -file crc16.tcl
51675
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Pat Thoyts
cksum(n) , crc32(n) , sum(n)
checksum , cksum , crc , crc16 , crc32 , cyclic redundancy check , data integrity , security
Copyright © 2002, Pat Thoyts