#! perl -sw
use 5.010;
use strict;
use Inline C => Config => BUILD_NOISY => 1;
use Inline C => <<'END_C',  NAME => '_767001', CLEAN_AFTER_BUILD => 0;

U32 checksum( U32 sum, SV *buf ) {
    int i;
    int n = SvCUR( buf ) >> 2;
    U32 *p = (U32 *)SvPVX( buf );

    for( i = 0; i < n; ++i ) {
            sum ^= p[ i ];
        sum = ( ( sum & 0x7fffffff ) << 1 ) | ( sum >> 31 );
    }
    return sum;
}

END_C

use Time::HiRes qw[ time ];
use constant BUFSIZ => 64 * 1024;

my $start = time;

my $size = -s $ARGV[ 0 ];
die("File not a multiple of 4 bytes")
    unless ( $size % 4 ) == 0;

open my $fh, "<:raw", $ARGV[ 0 ]  or die;

my $sum = 0;
my $buf;

while( read( $fh, $buf, BUFSIZ ) ) {
    $sum = checksum( $sum, $buf );
}

say $sum;

printf "Took: %f seconds\n", time() -$start;

__END__
C:\test>767001-IC 767001-small.dat
2779316821
Took: 0.014622 seconds