Compress.java

Compress.java

contents ::

  App.java
  BitStreamInputStream.java
  BitStreamOutputStream.java
  Compress.java
  Decompress.java
  lzwScript
  input
  Makefile

package zzhao_ex9;
import java.util.*;
import java.io.*;

public class Compress{
    public static void main(String[] args){
         Compress tester=new Compress();
         String inputfilename = "";
         String outputfilename = "";
         try{
             if (args.length == 1){//ARGS="test"
                  inputfilename = args[0];
             }else{
                  BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
                  inputfilename ="test";
                  PrintWriter output= new PrintWriter(new BufferedWriter(new FileWriter(inputfilename)));

                  //BufferedWriter output = new BufferedWriter(new FileWriter(new File("test")));
                  String str="";
                  while((str=input.readLine())!=null){
                      output.print(str);
                  }
             }
             outputfilename = inputfilename + ".LZW";
             tester.compress(inputfilename, outputfilename);

         }catch(IOException e){System.out.println("Error: " + e);}
}//main

    public void compress(String inputfilename, String outputfilename)throws IOException{
         Vector string_table = new Vector();
         int MAX_SIZE=4000;
         //initialize the first 255 characters
         for(int i=0; i<256; i++)
             string_table.add(String.valueOf((char)i));

         int next_code = 256, intStr=0, intChar=0;

         BufferedInputStream breader = new BufferedInputStream(new FileInputStream(inputfilename));
         BufferedOutputStream outBuf = new BufferedOutputStream(new FileOutputStream(outputfilename));
         BitStreamOutputStream bwriter = new BitStreamOutputStream(outBuf, 12);

         intStr = breader.read();
         String aString= String.valueOf((char)intStr);

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

             String nextChar= String.valueOf((char)intChar);
             if(string_table.contains(aString + nextChar)){
                  aString = aString + nextChar;

             }else{
                  int i=string_table.indexOf(aString);
                  bwriter.writeBitField(i);
                  string_table.add(aString + nextChar);
                  aString = nextChar;
             }

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


         }// end while

         int i=string_table.indexOf(aString);
         bwriter.writeBitField(i);//write aString

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

         bwriter.close();
         breader.close();

         //for testing only-table ok
         //for(int i=0; i<string_table.size(); i++)
         //if(i>255)
         //System.out.println(" in hashtable:  "
         // + i + "    " + (String)string_table.elementAt(i));
    }// compress
}

James Little