BRIEF DESCRIPTION
=================

This software is an implementation of LZ77 algorithm. He's a dictionary-based algorithm and keeps track of the last n bytes of data seen, and when a phrase is encountered that has already been seen, it outputs a pair of values corresponding to the position of the phrase 
in the previously-seen buffer of data, and the length of the phrase. Decompression is simple and fast: whenever a <LENGTH, POSITION> pair is encountered, go to that POSITION in the window and copy LENGTH bytes to the output.

The structure data is a text window divided in two parts, a dictionary and a look ahead buffer. The first is composed of data already encoded and the second contain the data to be encoded.

NOTE
====

In order to be supported in a network applications the couples are "coded" in network format using htons() and in decompression side it's used ntohs() function.


HOW TO BUILD 
============

To build these files you must have GNU make and gcc compiler. Open the shell terminal, go in to the directory where you find this file and type

	make

after this you can find an executable called lz77.

USAGE
=====

Usage : ./lz77 [options]

Options :

  -c	Set compression mode
  -d	Set decompression mode
  -i FILE
	Filename input (source).
	In compression mode if it isn't specify the software use the standard input,
	instead in decompression mode you must specify it.
  -o FILE
	File name output (destination).
	In decompression mode if it isn't specify the software use the standard output,
	instead in compression mode you must specify it.
  -t DICTIONARY
	Specify which dictionary you want to use
	The default one is 'it'. The name must be of 2 characters.
  -l VALUE
	Set look-ahead length, must specify a positive value.
	Min value is 8 and the max value is 255
  -w VALUE
	Set window length, must specify a positive value.
	Min value must be equal to look ahead length the max value is 32767.
  -v	Set verbose mode

EXAMPLES
========

	Using files  ./lz77 -c -i original_file -o compress_file -w 1024 -l 16 -t it
	Using STDIN  ./lz77 -c -o compress_file -w 1024 -l 16 -t it
	Using STDOUT ./lz77 -i compress-file -w 1024 -l 16 -t it

NOTE
=====

  If you're using the STDIN typing the text manually use Ctrl+D to do EOF.

CREDITS
=======

Author Pischedda Alessandro
E-mail [email protected]