/* decode.c                                  */
/* Program for Lempel-Ziv decompression */

#include <assert.h>
#include <stdio.h>
#include  <string.h>
#include <stdlib.h>

#include "lz.h"    /* contains global constants  and datastructures*/
#include "decode.h" /* defines the ADT for encoding */
#include "bits.h"
#include "dict.h"



  

/*-------------------------------------------------------------------*/
int main(int argc, char *argv[])
{
 
  FILE 			*f_in, *f_out;
  double		start_time, end_time;
  char           input_file_name[100],output_file_name[100];
  int BPC;   /*bits per code*/


/* From the standard input, read the name of input and output file */
/* names. Encode the input file and store the compressed data into */
/* output file                                                     */
/* read the input and output filenames */
printf("ENTER THE NAME OF FILE TO BE UNCOMPRESSED   "); 
scanf("%s",input_file_name); 
printf("\nENTER THE OUTPUT FILE NAME    "); 
scanf("%s",output_file_name); 
printf("\nBITS PER CODE USED (SHOULD BE BETWEEN 8 and 31) "); 
scanf("%d",&BPC); printf("\n");
/* open the input file for reading */
/* the option "rb" signifies that we will be reading */
/* from the input file as a binary file */
/* "r" is for read and "b" for binary */
f_in = fopen(input_file_name,"rb");
assert(f_in != NULL); /* if error in opening file, exit */

/* open the output file for writing */
/* the option "wb" is for binary write */
f_out = fopen(output_file_name,"wb");
assert(f_out != NULL);

/* start clock */
start_time = clock();
/* decode the data */
LZdecode(f_in, f_out,BPC);
/* end clock */
end_time = clock();

/* Print the statistics */
/* Print statistics */
printf("Total time = %f secs\n",(end_time-start_time)/CLOCKS_PER_SEC);

/* close the files*/
fclose(f_in);
fclose(f_out); 

return(1);
} /* end of main */

/*-----------------------------------------------------------------------*/
void LZdecode(FILE *in, FILE *out, int BPC)
{
/* encode the data */
/* an inefficient implementation !!! */

int input;
                 
char curr_string[MAX_MATCH_LENGTH], prev_string[MAX_MATCH_LENGTH];
DICT_TYPE dict;
/* initialize the dictionary */
dict = init_dict(BPC);


/* read the first input code */
input = getCode(BPC,in);
prev_string[0] = '\0';

/* read codes from the input file. LAST_CODE is the last code in */ /* the input file. So, if we encounter that, we know that we have*/ /* reached the end of file */ while(input != LAST_CODE) 
{
int length;
length = strlen(prev_string);
/* Look in the dictionary associated with the code input */

dict_string_lookup(input,curr_string,dict);
if (curr_string[0] != '\0')  
  {

/* we found the string */
/* insert into the dictionary the code corresponding to the */
   /* string formed by taking prev_string and attaching the    */
   /* first character of curr_string to it                  */
/* also, write curr_string in the output string */ /* also output curr_string into the output file */ fprintf(out,"%s",curr_string); if (prev_string[0] != '\0' )
    {
prev_string[length] = curr_string[0];
prev_string[length+1] = '\0';
insert_dict(prev_string,dict);
    }
strcpy(prev_string, curr_string);
input = getCode(BPC,in);
  
   }
   
else
   {
/* we must figure out the string ourselves */
/* the string must be same as prev_string  */
/* followed by the first character of      */
/* prev_string */
prev_string[length] = prev_string[0];
prev_string[length+1] = '\0';
     
/* insert this string into the dictionary */
/* and output is as well */ 
fprintf(out,"%s",prev_string);
insert_dict(prev_string,dict);
input = getCode(BPC,in);
    }
} /* while ... */

}