bitoutputstream.java

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package com.jr81.source.compression;

/*
 * BitOutputStream.java
 *
 * Created on 04 Dec 2006
 */

import java.io.* ;

/**
 *
 * @author  Moshe Fresko
 * @course	Algorithmic Programming 1
 * @exercise	2
 */

public class BitOutputStream extends FilterOutputStream
{
	class BitManager {
		int  buf = 0 ;
		int  cnt = 0 ;
			// Returns -1 if there is nothing yet to be written
		int  writeOne(int next)
			{ int ret = -1 ;
				buf=buf*2+next ;
				cnt++ ;
				if (cnt==7) {
					cnt = 0 ;
					ret = buf ;
					buf = 0 ;
				} else {
					ret = -1 ;
				}
				return ret ; }
			//
		int  writeLast()
			{ int x=0 ;
				for (int i=0;i<7-cnt;++i)
					x=x*2+1 ;
				for (int i=7-cnt;i<8;++i)
					x=x*2 ;
				return buf|x ; }
	}
	BitManager bitManager = new BitManager() ;
    	/** Constructor creates a new instance of BitOutputStream,
    	 	A decarotor to OutputStream, via FilterOutputStream */
	public BitOutputStream(OutputStream os)
		{ super(os) ; }
    	/** Writes a single bit into the included stream.
    	 	Although the input is a single bit, it is given as an int.
    	 	If it is non-zero, it is threated as 1. */
	public void write(int i) throws IOException
		{ int x = bitManager.writeOne(i>=1?1:0) ;
			if (x>=0)
				out.write(x) ; }
		/** Writes a list of bits given in the byte array as 0's and 1's */
	public void write(byte[] arr) throws IOException
		{ write(arr,0,arr.length) ; }

	public void write(byte[] arr, int off, int len) throws IOException
		{ int clen = 0 ;
			for (int i=0;i<len;++i) {
				int x = bitManager.writeOne(arr[off+i]) ;
				if (x>=0)
					arr[off+(clen++)]=(byte)x ;
			}
			out.write(arr,off,clen) ; }
    	/** Closes the included stream. Before closing flushes the necessary buffer.
    		Flush writes the partial byte kept in the internal buffer. */

  public void flush() throws IOException
  	{ out.write(bitManager.writeLast()) ;
  		super.flush() ; }
		// "Main" reads a file in the form of characters of '0's and '1's
		// and prints them as bits into another file as a BitStream

	public static void main(String[] args)
	{
		if (args.length<2)
		{
			System.out.println("Usage: java BitOutputStream FromFile ToFile") ;
			System.out.println("where 'FromFile' includes characters of '0' and '1'") ;
			System.out.println("and they are written as bits into 'ToFile'") ;
			System.exit(1) ;
		}

		try {
			InputStream is = new BufferedInputStream(new FileInputStream(args[0])) ;
			OutputStream os = new BitOutputStream(new BufferedOutputStream(new FileOutputStream(args[1]))) ;
			int next ;
			while ((next=is.read())>=0) {
				char ch = (char) next ;
				if (ch=='0' || ch=='1')
					os.write((int)(ch-'0')) ;
			}
			is.close() ;
			os.close() ;
		} catch (FileNotFoundException fnfe) {
			System.out.println(args[0]+" file not found") ;
			System.exit(1) ;
		} catch (IOException ioe) {
			System.out.println("Error in reading file "+args[0]+" or writing file "+args[1]) ;
			System.exit(1) ;
		}
	}
}