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ActiveTcl User Guide
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[ Main table Of Contents | Tcllib Table Of Contents | Tcllib Index ]
crc32(n) 1.2 "Cyclic Redundancy Check (crc32)"
crc32 - Perform a 32bit Cyclic Redundancy Check
TABLE OF
CONTENTS
SYNOPSIS
DESCRIPTION
COMMANDS
OPTIONS
EXAMPLES
AUTHORS
SEE ALSO
KEYWORDS
COPYRIGHT
package require Tcl 8.2
package require crc32 ?1.2?
This package provides a Tcl-only implementation of the CRC-32
algorithm based upon information provided at
http://www.naaccr.org/standard/crc32/document.html If the
Trf package is available then the crc-zlib command is used to perform the calculation.
- ::crc::crc32 ?-format format? ?-seed value? ?-implementation
procname? message
- ::crc::crc32 ?-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-32 algorithm. 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 0xffffffff. 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.
Note that as the Trf command crc-zlib cannot accept a seed value, use of this option
will force the use of the Tcl only implementation.
- -implementation procname
- This hook is provided to allow users to provide their own
implementation (perhaps a C compiled extension) or to explicitly
request use of the Tcl only implementation when
Trf is installed (by setting -implementation crc::Crc32_tcl. The procedure specfied is
called with two parameters. The first is the data to be checksummed
and the second is the seed value. A 32bit integer is expected as
the result.
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% crc::crc32 "Hello, World!"
3964322768
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% crc::crc32 -format 0x%X "Hello, World!"
0xEC4AC3D0
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% crc::crc32 -file crc32.tcl
483919716
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Pat Thoyts
cksum(n) , crc16(n) , sum(n)
checksum , cksum , crc , crc32 , cyclic redundancy check , data integrity , security
Copyright © 2002, Pat Thoyts