Decompress.java

Decompress.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.decompress;

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

public class Decompress {
    private static Decompress  a;
    private static BitStreamInputStream reader;
    private static BufferedOutputStream writer;
    private static String outputfilename;

    public static void main(String [] args){
         String inputfilename = "";
         String outputfilename = "";
         try{
             if (args.length == 1){//ARGS="test"
                  inputfilename = args[0];
                  outputfilename = inputfilename + ".DEC";

                  // open input streams
                  FileInputStream inFile = new FileInputStream(inputfilename);
                  BufferedInputStream in = new BufferedInputStream(inFile);
                  reader = new BitStreamInputStream(in, 12);

                  //open output streams
                  FileOutputStream outFile = new FileOutputStream(outputfilename);
                  writer = new BufferedOutputStream(outFile);

             }else{

                  reader = new BitStreamInputStream(System.in, 12);
                  writer = new BufferedOutputStream(System.out);

         }

         }catch(IOException e){
             System.out.println("Error: " + e);
             System.exit(1);
         }
         a = new Decompress();
         a.decompress();
    }


    // decompression routine
    public void decompress(){
         int MAX_VALUE = 4000;
         //    System.out.println("decompressing...... ");
         // once we get to here we are going
         // to have to flush the table

         Vector string_table = new Vector();

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

         int oldCode = 0, newCode = 0;

         try{

             String aString = "", aChar = "";

             oldCode = (int)reader.readBitField();
             if(oldCode!=-1){
                  aChar = String.valueOf((char)oldCode);

                  writer.write(oldCode);  // looks like it should be aChar.. but done with oldCode??

                  // loop through the rest of the characters
                  while((newCode=(int)reader.readBitField())!=-1) {

                      if(newCode >= string_table.size()){
                           aString = (String)string_table.get(oldCode);
                           aString = aString + aChar;
                      } else aString = (String)string_table.get(newCode);

                      writer.write(aString.getBytes());
                      aChar = aString.substring(0,1);
                      string_table.add((String)string_table.get(oldCode)+aChar);
                      oldCode = newCode;

                      if(string_table.size()>MAX_VALUE){
                           string_table.removeAllElements();
                           for(int i=0; i<256; i++){
                               string_table.add(String.valueOf((char)i));
                           }
                      }

                  } // end while
             }// end if the file is empty
             reader.close();
             writer.close();
         } catch(IOException e){
             System.out.println("ERROR: "+e);
             System.exit(1);
         }

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

    }// end decompress

} // end App

James Little