bytebuffer.java

java jdk 1.4的源码

/*
 * @(#)ByteBuffer.java	1.4 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package com.sun.corba.se.internal.ior ;


public class ByteBuffer {
    /**
     * The array buffer into which the components of the ByteBuffer are
     * stored. The capacity of the ByteBuffer is the length of this array buffer, 
     * and is at least large enough to contain all the ByteBuffer's elements.<p>
     *
     * Any array elements following the last element in the ByteBuffer are 0.
     */
    protected byte elementData[];

    /**
     * The number of valid components in this <tt>ByteBuffer</tt> object. 
     * Components <tt>elementData[0]</tt> through 
     * <tt>elementData[elementCount-1]</tt> are the actual items.
     *
     * @serial
     */
    protected int elementCount;

    /**
     * The amount by which the capacity of the ByteBuffer is automatically 
     * incremented when its size becomes greater than its capacity.  If 
     * the capacity increment is less than or equal to zero, the capacity
     * of the ByteBuffer is doubled each time it needs to grow.
     *
     * @serial
     */
    protected int capacityIncrement;

    /**
     * Constructs an empty ByteBuffer with the specified initial capacity and
     * capacity increment. 
     *
     * @param   initialCapacity     the initial capacity of the ByteBuffer.
     * @param   capacityIncrement   the amount by which the capacity is
     *                              increased when the ByteBuffer overflows.
     * @exception IllegalArgumentException if the specified initial capacity
     *               is negative
     */
    public ByteBuffer(int initialCapacity, int capacityIncrement) {
	super();
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
	this.elementData = new byte[initialCapacity];
	this.capacityIncrement = capacityIncrement;
    }

    /**
     * Constructs an empty ByteBuffer with the specified initial capacity and 
     * with its capacity increment equal to zero.
     *
     * @param   initialCapacity   the initial capacity of the ByteBuffer.
     * @exception IllegalArgumentException if the specified initial capacity
     *               is negative
     */
    public ByteBuffer(int initialCapacity) {
	this(initialCapacity, 0);
    }

    /**
     * Constructs an empty ByteBuffer so that its internal data array 
     * has size <tt>10</tt> and its standard capacity increment is 
     * zero. 
     */
    public ByteBuffer() {
	this(200);
    }

    /**
     * Trims the capacity of this ByteBuffer to be the ByteBuffer's current 
     * size. If the capacity of this cector is larger than its current 
     * size, then the capacity is changed to equal the size by replacing 
     * its internal data array, kept in the field <tt>elementData</tt>, 
     * with a smaller one. An application can use this operation to 
     * minimize the storage of a ByteBuffer. 
     */
    public void trimToSize() {
	int oldCapacity = elementData.length;
	if (elementCount < oldCapacity) {
	    byte oldData[] = elementData;
	    elementData = new byte[elementCount];
	    System.arraycopy(oldData, 0, elementData, 0, elementCount);
	}
    }

    /**
     * This implements the unsynchronized semantics of ensureCapacity.
     * Synchronized methods in this class can internally call this 
     * method for ensuring capacity without incurring the cost of an 
     * extra synchronization.
     *
     * @see java.util.ByteBuffer#ensureCapacity(int)
     */ 
    private void ensureCapacityHelper(int minCapacity) {
	int oldCapacity = elementData.length;
	if (minCapacity > oldCapacity) {
	    byte oldData[] = elementData;
	    int newCapacity = (capacityIncrement > 0) ?
		(oldCapacity + capacityIncrement) : (oldCapacity * 2);
    	    if (newCapacity < minCapacity) {
		newCapacity = minCapacity;
	    }
	    elementData = new byte[newCapacity];
	    System.arraycopy(oldData, 0, elementData, 0, elementCount);
	}
    }

    /**
     * Returns the current capacity of this ByteBuffer.
     *
     * @return  the current capacity (the length of its internal 
     *          data arary, kept in the field <tt>elementData</tt> 
     *          of this ByteBuffer.
     */
    public int capacity() {
	return elementData.length;
    }

    /**
     * Returns the number of components in this ByteBuffer.
     *
     * @return  the number of components in this ByteBuffer.
     */
    public int size() {
	return elementCount;
    }

    /**
     * Tests if this ByteBuffer has no components.
     *
     * @return  <code>true</code> if and only if this ByteBuffer has 
     *          no components, that is, its size is zero;
     *          <code>false</code> otherwise.
     */
    public boolean isEmpty() {
	return elementCount == 0;
    }

    public void append(byte value) 
    {
	ensureCapacityHelper(elementCount + 1);
	elementData[elementCount++] = value;
    }

    public void append( int value ) 
    {
	ensureCapacityHelper(elementCount + 4);
	doAppend( value ) ;
    }

    private void doAppend( int value )
    {
	int current = value ;
	for (int ctr=0; ctr<4; ctr++) {
	    elementData[elementCount+ctr] = (byte)(current & 255) ;
	    current = current >> 8 ;
	}
	elementCount += 4 ;
    }

    public void append( String value ) 
    {
	byte[] data = value.getBytes() ;
	ensureCapacityHelper( elementCount + data.length + 4 ) ;
	doAppend( data.length ) ;
	System.arraycopy( data, 0, elementData, elementCount, data.length ) ;
	elementCount += data.length ;
    }

    /**
     * Returns an array containing all of the elements in this ByteBuffer
     * in the correct order.
     *
     * @since 1.2
     */
    public byte[] toArray() {
	return elementData ;
    }
}