Calculate movie hash

PHP code to calculate the movie Hash.

Uses size + 64bit chksum of the first and last 64k (even if they overlap because the file is smaller than 128k)

Usage:

echo OpenSubtitlesHash("/home/chema/Desktop/Monty Pythons Life of Brian.avi");

Code:

function OpenSubtitlesHash($file)
{
    $handle = fopen($file, "rb");
    $fsize = filesize($file);

    $hash = array(3 => 0,
                  2 => 0,
                  1 => ($fsize >> 16) & 0xFFFF,
                  0 => $fsize & 0xFFFF);

    for ($i = 0; $i < 8192; $i++)
    {
        $tmp = ReadUINT64($handle);
        $hash = AddUINT64($hash, $tmp);
    }

    $offset = $fsize - 65536;
    fseek($handle, $offset > 0 ? $offset : 0, SEEK_SET);

    for ($i = 0; $i < 8192; $i++)
    {
        $tmp = ReadUINT64($handle);
        $hash = AddUINT64($hash, $tmp);
    }

    fclose($handle);
        return UINT64FormatHex($hash);
}

function ReadUINT64($handle)
{
    $u = unpack("va/vb/vc/vd", fread($handle, 8));
    return array(0 => $u["a"], 1 => $u["b"], 2 => $u["c"], 3 => $u["d"]);
}

function AddUINT64($a, $b)
{
    $o = array(0 => 0, 1 => 0, 2 => 0, 3 => 0);

    $carry = 0;
    for ($i = 0; $i < 4; $i++)
    {
        if (($a[$i] + $b[$i] + $carry) > 0xffff )
        {
            $o[$i] += ($a[$i] + $b[$i] + $carry) & 0xffff;
            $carry = 1;
        }
        else
        {
            $o[$i] += ($a[$i] + $b[$i] + $carry);
            $carry = 0;
        }
    }

    return $o;
}

function UINT64FormatHex($n)
{
    return sprintf("%04x%04x%04x%04x", $n[3], $n[2], $n[1], $n[0]);
}

source