lib/pack-codec.js
function $num(byte) {
    num = (num << 8) | byte;
    if (++offset < 4) return $num;
    offset = 0;
    emit({version: version, num: num});
    return $header;
  }
function $num(byte) {
    num = (num << 8) | byte;
    if (++offset < 4) return $num;
    offset = 0;
    emit({version: version, num: num});
    return $header;
  }
The number of objects in this packfile is also stored as an unsigned 32 bit int.