//*********************************************************************
//
// Lempel-Ziv based data uncompression
//   Copyright  Ver 1.0
// ECE of UMass-Amherst   March 10, 98
//
//*********************************************************************

#include <stdio.h>
#define L_WIN 128 
#define L_LOOK 64
#define L L_WIN+L_LOOK

main(int argc, char *argv[])
{
	unsigned char x[L+1];	// use last one to save at all-matching
	unsigned pointer=0, matchLength=0, lastSymbol=0;
	int i, j, gameOver=0;

	FILE *p1, *p2;

	if(argc < 3){
		printf("Usage: unlz77 zipfile outputfile\n");
		exit(1);
	}
	if( (p1=fopen(argv[1], "r")) == NULL){
		printf("\nThe file %s not exist!\n", argv[1]);
		exit(0);
	}
	if( (p2=fopen(argv[2], "w")) == NULL){
		printf("\nThe file %s can't be opened!\n", argv[2]);
		exit(0);
	}

	// initialize sliding window & look-ahead buffer
	for(i=1; i<=L+1; i++)
		x[i] = 0;
	
     do{
		fread( &pointer, 1, 1, p1); 	// pointer, matchLength must be initialized!!
		fread( &matchLength, 1, 1, p1);
		fread( &lastSymbol, 1, 1, p1);
	if(feof(p1)) gameOver = 1;

	if(matchLength == 0){
		x[L_WIN+1] = lastSymbol;	
		if(!gameOver) fwrite( &lastSymbol, 1, 1, p2);
	}
	else {
	 	for(i=1; i<=matchLength; i++){
			x[L_WIN+i] = x[pointer+i-1];
			fwrite( &x[L_WIN+i],1,1, p2);
			x[L_WIN+matchLength+1] = lastSymbol;
		}
		if(!gameOver) fwrite( &lastSymbol, 1, 1,p2);
	}
	
	for(i=1; i<=L_WIN; i++)		// shift
		x[i] = x[i+matchLength+1];
   }while( !gameOver );

  fclose(p1);
  fclose(p2);
}