#! /usr/bin/perl

use strict;
use warnings;

# calculate CRC32
sub crc32
{
  my $bytes = shift; # array reference

  my @tab = (
    0x77073096, 0xEE0E612C, 0x076DC419, 0x0EDB8832,
    0x1DB71064, 0x3B6E20C8, 0x76DC4190, 0xEDB88320
  );

  my $crc = 0xFFFFFFFF;
  for (my $i = 0; $i < @{$bytes}; ++$i) {
    my $val = $crc ^ @{$bytes}[$i];
    $crc >>= 8;
    for (my $b = 0; $b < 8; ++$b) {
      if ($val & 1 << $b) {
        $crc ^= $tab[$b];
      }
    }
  }
  $crc ^= 0xFFFFFFFF;

  $crc = [
    $crc & 0xFF,
    $crc >> 8 & 0xFF,
    $crc >> 16 & 0xFF,
    $crc >> 24 & 0xFF
  ];

  return $crc; # array reference
}

1;