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//******************************************************************************
//
// File: InputBitStream.java
// Package: edu.rit.image
// Unit: Class edu.rit.image.InputBitStream
//
// This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.image;
import java.io.DataInputStream;
import java.io.IOException;
/**
* Class InputBitStream provides an object for reading a stream of bits from an
* input stream.
*
* @author Alan Kaminsky
* @version 08-Apr-2008
*/
class InputBitStream
{
// Hidden data members.
private DataInputStream dis;
private int inData;
private int inBits;
// Exported constructors.
/**
* Construct a new input bit stream on top of the given data input
* stream.
*
* @param dis Data input stream.
*/
public InputBitStream
(DataInputStream dis)
{
this.dis = dis;
}
// Exported operations.
/**
* Peek ahead at the given number of bits, but do not consume them.
*
* @param bits Number of bits to peek.
*
* @return Bits peeked, at the least significant end of the int.
*
* @exception IOException
* Thrown if an I/O error occurred.
*/
public int peekBits
(int bits)
throws IOException
{
// Make sure we've read enough bits.
while (inBits < bits)
{
inData = (inData << 8) | dis.readUnsignedByte();
inBits += 8;
}
// Shift the given number of bits to the right end and mask them in.
return (inData >> (inBits - bits)) & (~ (0xFFFFFFFF << bits));
}
/**
* Read and consume the given number of bits.
*
* @param bits Number of bits to read.
*
* @return Bits read, at the least significant end of the int.
*
* @exception IOException
* Thrown if an I/O error occurred.
*/
public int readBits
(int bits)
throws IOException
{
// Make sure we've read enough bits.
while (inBits < bits)
{
inData = (inData << 8) | dis.readUnsignedByte();
inBits += 8;
}
// Shift the given number of bits to the right end and mask them in.
int b = (inData >> (inBits - bits)) & (~ (0xFFFFFFFF << bits));
// Consume the given number of bits.
inBits -= bits;
return b;
}
/**
* Skip over and consume the given number of bits.
*
* @param bits Number of bits to skip.
*
* @exception IOException
* Thrown if an I/O error occurred.
*/
public void skipBits
(int bits)
throws IOException
{
// Make sure we've read enough bits.
while (inBits < bits)
{
inData = (inData << 8) | dis.readUnsignedByte();
inBits += 8;
}
// Consume the given number of bits.
inBits -= bits;
}
}
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