util/src/main/java/org/apache/etch/util/ByteBuffer.java

/* $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.etch.util;

import java.io.EOFException;
import java.nio.BufferOverflowException;

/**
 * Byte buffer with operation to support getting and putting
 * bytes.
 */
abstract public class ByteBuffer
{
	/**
	 * @return true if the buffer is empty.
	 */
	public boolean isEmpty()
	{
		return length() == 0;
	}

	/**
	 * @return true if the buffer is full.
	 */
	public boolean isFull()
	{
		return length() == size();
	}
	
	/**
	 * @return the amount of data the buffer can hold.
	 */
	abstract public int size();
	
	/**
	 * @return the amount of data in the buffer.
	 */
	abstract public int length();
	
	/**
	 * @return the next byte from the buffer.
	 * @throws EOFException if the buffer is empty.
	 */
	abstract public byte get() throws EOFException;
	
	/**
	 * Gets bytes from the buffer to fill buf.
	 * @param buf
	 * @return the length of data put into buf.
	 */
	public int get( byte[] buf )
	{
		return get( buf, 0, buf.length );
	}
	
	/**
	 * Gets bytes from the buffer to fill buf, starting at the specified
	 * position for the specified length.
	 * @param buf
	 * @param off
	 * @param len
	 * @return the length of data put into buf.
	 */
	public int get( byte[] buf, int off, int len )
	{
		if (off < 0)
			throw new IllegalArgumentException( "off < 0" );
		
		if (len < 0)
			throw new IllegalArgumentException( "len < 0" );
		
		if (off+len > buf.length)
			throw new IllegalArgumentException( "off+len > buf.length" );
		
		if (len == 0)
			return 0;

		int count = 0;
		try
		{
			while (len > 0)
			{
				buf[off] = get();
				count++;
				off++;
				len--;
			}
		}
		catch ( EOFException e )
		{
			// nothing to do.
		}
		return count;
	}
	
	/**
	 * Puts a byte into the buffer.
	 * @param b
	 * @throws BufferOverflowException if the buffer is full
	 */
	abstract public void put( byte b ) throws BufferOverflowException;
	
	/**
	 * Puts the bytes from buf into the buffer.
	 * @param buf
	 * @return the amount of data copied into the buffer.
	 */
	public int put( byte[] buf )
	{
		return put( buf, 0, buf.length );
	}
	
	/**
	 * Puts the bytes from buf into the buffer, starting at the specified
	 * position for the specified length;
	 * @param buf
	 * @param off
	 * @param len
	 * @return the amount of data copied into the buffer.
	 */
	public int put( byte[] buf, int off, int len )
	{
		if (off < 0)
			throw new IllegalArgumentException( "off < 0" );
		
		if (len < 0)
			throw new IllegalArgumentException( "len < 0" );
		
		if (off+len > buf.length)
			throw new IllegalArgumentException( "off+len > buf.length" );
		
		if (len == 0)
			return 0;
		
		int count = 0;
		try
		{
			while (len > 0)
			{
				put( buf[off] );
				count++;
				off++;
				len--;
			}
		}
		catch ( BufferOverflowException e )
		{
			// nothing to do.
		}
		return count;
	}
	
	/**
	 * Clears the buffer.
	 */
	abstract public void clear();
	
	/**
	 * @return a little-endian 32-bit integer from the buffer.
	 * @throws EOFException
	 */
	public int getInt() throws EOFException
	{
		int b0 = get() & 255;
		int b1 = get() & 255;
		int b2 = get() & 255;
		int b3 = get() & 255;
		return b0 | b1 << 8 | b2 << 16 | b3 << 24;
	}
	
	/**
	 * Puts a little-endian 32-bit integer into the buffer.
	 * @param x
	 */
	public void putInt( int x )
	{
		put( (byte) x );
		put( (byte) (x >>> 8) );
		put( (byte) (x >>> 16) );
		put( (byte) (x >>> 24) );
	}
}