nction value) has occurred recently, the compressor
   compares all strings on the XYZ hash chain with the actual input data
   sequence starting at the current point, and selects the longest
   match.

   The compressor searches the hash chains starting with the most recent
   strings, to favor small distances and thus take advantage of the
   Huffman encoding.  The hash chains are singly linked. There are no
   deletions from the hash chains; the algorithm simply discards matches
   that are too old.  To 