if isinstance(value, (int, long)):

1. TODO this is a really ugly way to check for this...
   if value > 2 ** 64 / 2 - 1 or value < -2 ** 64 / 2:
   raise OverflowError("BSON can only handle up to 8-byte ints")
   if value > 2 ** 32 / 2 - 1 or value < -2 ** 32 / 2:
   return "\x12" + name + struct.pack("<q", value)
   return "\x10" + name + struct.pack("<i", value)

This is a really ugly way and it does not allow to store long (>2**32) value, which was stored as zero and then $inc'ed.