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#!/usr/bin/perl -w
# Subroutine crc32(): Calculates the CRC on a given string.
{
my @table = ();
# @brief Calculate CRC32 for a given string.
sub crc32
{
unless (@table) {
# Initialize the CRC table
my $poly = 0xEDB88320;
@table = ();
for my $i (0..255) {
my $c = $i;
for my $j (0..7) {
$c = ($c & 1) ? (($c >> 1) ^ $poly) : ($c >> 1);
}
$table[$i] = $c;
}
}
my $s = shift; # string to calculate the CRC for
my $crc = shift; # CRC start value
defined($crc)
or $crc = 0xffffffff; # Default CRC start value
for (my $i = 0; $i < length($s); $i++) {
$crc = $table[($crc ^ ord(substr($s, $i, 1))) & 0xff]
^ ($crc >> 8);
}
return $crc;
}
}
sub crc32_on_file
{
my $file = shift;
my $crc32 = crc32('');
my $buf = '';
my $ret = 0;
while ($ret = read($file, $buf, 8192)) {
$crc32 = crc32($buf, $crc32);
}
defined($ret)
or return undef;
printf("0x%x\n", $crc32);
}
# Main routine: Calculate the CRCs on the given files and print the
# results.
{
if (@ARGV) {
while (my $path = shift) {
my $file;
open $file, "<", $path
or die "Error opening '$path'.\n";
&crc32_on_file($file)
or die "Error reading from '$path'.\n";
close $file;
}
} else {
&crc32_on_file(\*STDIN)
or die "Error reading from stdin.\n";
}
}
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