32K input bytes before.

   Each block consists of two parts: a pair of Huffman code trees that
   describe the representation of the compressed data part, and a
   compressed data part.  (The Huffman trees themselves are compressed
   using Huffman encoding.)  The compressed data consists of a series of
   elements of two types: literal bytes (of strings that have not been
   detected as duplicated within the previous 32K input bytes), and
   pointers to duplicated strings, where a pointer is represented a