Compress.java

Compress.java

contents ::

/* James Little 5-5-01
   I hope this is one of the last programs I have to write in this course.
*/

package jlittle_ex9.compress;

import java.io.*;
import java.util.*;
import util241.*;

public class Compress {
    private static BufferedInputStream reader;
    private static BitStreamOutputStream writer;
    private static String outputfilename = "";

    public static void main(String [] args){
         String inputfilename = null;

         Compress a = new Compress();

         try{
             if (args.length != 0){
                  inputfilename = args[0];
                  outputfilename = inputfilename + ".LZW";

                  // open input streams
                  FileInputStream inFile = new FileInputStream(inputfilename);
                  BufferedInputStream reader = new BufferedInputStream(inFile);

                  //open output streams
                  FileOutputStream outFile = new FileOutputStream(outputfilename);
                  BufferedOutputStream outBuf = new BufferedOutputStream(outFile);
                  writer = new BitStreamOutputStream(outBuf, 12);

             }else{
                  reader = new BufferedInputStream(System.in);
                  writer = new BitStreamOutputStream(System.out, 12);

             }

         }catch(IOException e){System.out.println("Error: " + e + "\nFilename : "+inputfilename);}
         a.compress();
    }

    // compression routine
    public void compress(){

         int MAX_VALUE = 4000;
         Vector string_table = new Vector();

         for(int i=0; i<256; i++){
             string_table.add(String.valueOf((char)i));
         }

         //         System.out.println("I am now compressing...");
         int next_code = 256, intStr = 0, intChar=0;

         try{
             intStr = reader.read();
             if(intStr!=-1){
                  String aString = String.valueOf((char)intStr);
                  String nextChar = "";
                  int i = 0;

                  while((intChar = reader.read())!=-1){

                      nextChar = String.valueOf((char)intChar);
                      if(string_table.contains(aString + nextChar)){
                           aString = aString + nextChar;
                      }else{
                           i = string_table.indexOf(aString);
                           writer.writeBitField(i);
                           string_table.add(aString + nextChar);
                           aString = nextChar;
                      } // end if
                      if(string_table.size()>MAX_VALUE){
                           string_table.removeAllElements();
                           for(int j=0; j<256; j++){
                               string_table.add(String.valueOf((char)j));
                           }
                      }
                  } // end while

                  i = string_table.indexOf(aString);
                  writer.writeBitField(i); // write a string
             }// end of initial is the file empty?? if
             writer.close();
             reader.close();
         } catch(IOException e){
             System.out.println("ERROR: " + e);
             System.exit(1);
         }

         //for(int j=256; j<string_table.size() ; j++){
         //         System.out.println("\t"+string_table.size());
         //}


    } // end compress
} // end App

James Little