avoid a worst-case situation, very long hash
   chains are arbitrarily truncated at a certain length, determined by a
   run-time parameter.

   To improve overall compression, the compressor optionally defers the
   selection of matches ("lazy matching"): after a match of length N has
   been found, the compressor searches for a longer match starting at
   the next input byte.  If it finds a longer match, it truncates the
   previous match to a length of one (thus producing a single literal
   byte) and th