To BOM sniff an I/O queue of bytes ioQueue, run these steps:

1. Let BOM be the result of peeking 3 bytes from ioQueue, converted to a byte sequence.

2. For each of the rows in the table below, starting with the first one and going down, if BOM starts with the bytes given in the first column, then return the encoding given in the cell in the second column of that row. Otherwise, return null.

   Byte order mark	Encoding
   0xEF 0xBB 0xBF	UTF-8
   0xFE 0xFF	UTF-16BE
   0xFF 0xFE	UTF-16LE

This hook is a workaround for the fact that decode has no way to communicate back to the caller that it has found a byte order mark and is therefore not using the provided encoding. The hook is to be invoked before decode, and it will return an encoding corresponding to the byte order mark found, or null otherwise.