crc32--3tcl

crc32(n)                Cyclic Redundancy Check (crc32)               crc32(n)



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NAME
       crc32 - Perform a 32bit Cyclic Redundancy Check

SYNOPSIS
       package require Tcl  8.2

       package require crc32  ?1.1.1?

       ::crc::crc32  ?-format format? ?-seed value? ?-implementation procname?
       message

       ::crc::crc32 ?-format format? ?-seed value? ?-implementation  procname?
       -filename file

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DESCRIPTION
       This package provides a Tcl-only implementation of the CRC-32 algorithm
       based  upon   information   provided   at   http://www.naaccr.org/stan-
       dard/crc32/document.html  If the Trf package is available then the crc-
       zlib command is used to perform the calculation.

COMMANDS
       ::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.

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  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 imple-
              mentation  (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 spec-
              fied 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.

EXAMPLES
       % crc::crc32 "Hello, World!"
       3964322768

       % crc::crc32 -format 0x%X "Hello, World!"
       0xEC4AC3D0

       % crc::crc32 -file crc32.tcl
       483919716

AUTHORS
       Pat Thoyts

SEE ALSO
       cksum(n), crc16(n), sum(n)

KEYWORDS
       checksum, cksum, crc, crc32, cyclic redundancy check,  data  integrity,
       security

COPYRIGHT
       Copyright (c) 2002, Pat Thoyts



crc                                  1.1.1                            crc32(n)