crc16(n) Cyclic Redundancy Check (crc16) crc16(n)

NAME
       crc16 - Perform a 16bit Cyclic Redundancy Check

SYNOPSIS
       package require TTccll  88..22

       package require ccrrcc1166  ??11..11??

       ::::ccrrcc::::ccrrcc1166  ?-format format? ?-seed value? ?-implementation procname?
       message

       ::::ccrrcc::::ccrrcc1166 ?-format format? ?-seed value? ?-implementation  procname?
       -filename file

       ::::ccrrcc::::ccrrcc-cccciitttt  ?-format format? ?-seed value? ?-implementation proc-
       name? message

       ::::ccrrcc::::ccrrcc-cccciitttt ?-format format? ?-seed value? ?-implementation  proc-
       name? -filename file



DESCRIPTION
       This  package  provides a Tcl-only implementation of the CRC algorithms
       based   upon   information    provided    at    http://www.microconsul-
       tants.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.

CCOOMMMMAANNDDSS
       ::::ccrrcc::::ccrrcc1166  ?-format format? ?-seed value? ?-implementation procname?
       message

       ::::ccrrcc::::ccrrcc1166  ?-format format? ?-seed value? ?-implementation procname?
       -filename file

       ::::ccrrcc::::ccrrcc-cccciitttt  ?-format format? ?-seed value? ?-implementation proc-
       name? message

       ::::ccrrcc::::ccrrcc-cccciitttt  ?-format format? ?-seed value? ?-implementation proc-
       name? -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.

OOPPTTIIOONNSS
       -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 imple-
              mentation  (perhaps a C compiled extension). The procedure spec-
              fied 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.

EEXXAAMMPPLLEESS
       % 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
       cksum(n), crc32(n), sum(n)

KKEEYYWWOORRDDSS
       checksum, cksum, crc,  crc16,  crc32,  cyclic  redundancy  check,  data
       integrity, security

COPYRIGHT       Copyright (c) 2002, Pat Thoyts



crc                                   1.1                             crc16(n)