Manual Reference Pages - crc32_hash (3)

NAME

crc32_hash(3f) - [M_hashkeys] CRC (Cyclic Redundancy Check) (LICENSE:PD)

Synopsis
Description
Options
Returns
References
Author
Example

SYNOPSIS

function crc32_hash(a,continue) result (crc)

   class(*),intent(in)          :: anything(:)
   logical,intent(in),optional  :: continue
   integer(int64)               :: crc_out

DESCRIPTION

This ia 32-bit version of the Cyclic Redundancy Check(CRC). This variant of CRC-32 uses LSB-first order, sets the initial CRC to FFFFFFFF_int32, and complements the final CRC.
The result should be in accordance with ISO 3309, ITU-T V.42, Gzip and PNG.

OPTIONS

anything
input value to generate a CRC check for. May be a array or scalar of numeric or string values of type CHARACTER, int8, int16, int32, int64, real32, real64, real128

continue
optional parameter. If not present or .F. starts new CRC sum. If .T. continues a CRC starting with last CRC calculated.

RETURNS

crc The calculated CRC sum. It is calculated as a 32-bit value but returned as a 64-bit value, as Fortran does not currently support unsigned integers.

REFERENCES

Algorithms are described in "Computation of CRC" in Wikipedia. Also see
      https://en.wikipedia.org/wiki/Cyclic_redundancy_check

AUTHOR

This was derived from an unattributed example on http://rosettacode.org, but has been modified.

EXAMPLE

Sample program:

   program demo_crc32_hash
   use,intrinsic :: ISO_FORTRAN_ENV, only : int64
   use M_hashkeys, only : crc32_hash
   implicit none
   integer :: i
   integer(int64) :: crc
   character(*), parameter :: s = "The quick brown fox jumps over the lazy dog"
      ! string
      crc=crc32_hash(s)
      print "(Z8)", crc
      print "(i0)", crc
      ! character array
      print "(i0)", crc32_hash([ &
              & ’T’,’h’,’e’,’ ’,&
              & ’q’,’u’,’i’,’c’,’k’,’ ’,&
              & ’b’,’r’,’o’,’w’,’n’,’ ’,&
              & ’f’,’o’,’x’,’ ’])
      print "(i0)", crc32_hash([ &
              & ’j’,’u’,’m’,’p’,’s’,’ ’,&
              & ’o’,’v’,’e’,’r’,’ ’,&
              & ’t’,’h’,’e’,’ ’,&
              & ’l’,’a’,’z’,’y’,’ ’,&
              & ’d’,’o’,’g’],continue=.true.)
      ! numeric array
      print "(i0)", crc32_hash([(i,i=1,100)])
   end program demo_crc32_hash

Expected output:

414FA339 1095738169 2293265890 1095738169 1783575711

crc32_hash (3)

March 11, 2021

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