-- Just for fun, playing with the old Zip "Reduce" format...
--
-- "Reduce" combines the LZ77 method with a probabilistic
-- predictor using a Markov chain.
--
-- The format has a single block, then a single matrix,
-- for the whole data to be compressed :-(.
--
-- NB: this compressor works in two passes, the first pass
-- serving to compute the exact optimal Markov matrix for the whole
-- data to be compressed. Hence, it is slow. However,
-- we cache the last n=LZ_cache_size bytes compressed by LZ77.
-- The result is optimal within the constraints of that format
-- (one block, poor encoding of compressed data and of the
-- compression structure, the Markov matrix itself).
--
-- Author: G. de Montmollin, January 2009
--
private procedure Zip.Compress.Reduce(
input,
output : Zip_Streams.Zipstream_Class;
input_size_known: Boolean;
input_size : File_size_type; -- ignored if unknown
feedback : Feedback_proc;
method : Reduction_Method;
CRC : in out Interfaces.Unsigned_32; -- only updated here
output_size : out File_size_type;
compression_ok : out Boolean -- indicates when compressed <= uncompressed
);