gzencode and stream http archive

function stream_gz_encode($data, $compressed_size) {
  $size = strlen($data);
  $crc = crc32($data);
  $data = gzencode($data, 9);
  $data = substr_replace($data, pack('V', $crc), -8, 4);
  $data = substr_replace($data, pack('V', $size), -4, 4);
  $compressed_size += strlen($data);
  printf('%s%s%s%s%s',
    substr($data, 0, 4),
    pack('V', $crc),
    pack('V', $size),
    pack('v', strlen($data) - 12),
    substr($data, -(strlen($data) - 12))
  );
}