bytearray.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.iapi.util.ByteArray

   Copyright 1998, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed 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.derby.iapi.util;

import java.io.ObjectOutput;
import java.io.ObjectInput;
import java.io.IOException;

/**
	ByteArray wraps java byte arrays (byte[]) to allow
	byte arrays to be used as keys in hashtables.

	This is required because the equals function on
	byte[] directly uses reference equality.
	<P>
	This class also allows the trio of array, offset and length
	to be carried around as a single object.
*/
public final class ByteArray
{

	private byte[] array;
	private int    offset;
	private int    length;

	/**
		Create an instance of this class that wraps ths given array.
		This class does not make a copy of the array, it just saves
		the reference.
	*/
	public ByteArray(byte[] array, int offset, int length) {
		this.array = array;
		this.offset = offset;
		this.length = length;
	}

	public ByteArray(byte[] array) {
		this(array, 0, array.length);
	}

	public ByteArray()
	{
	}

	public void setBytes(byte[] array)
	{
		this.array = array;
		offset = 0;
		length = array.length;
	}	

	public void setBytes(byte[] array, int length)
	{
		this.array = array;
		this.offset = 0;
		this.length = length;
	}	

	public void setBytes(byte[] array, int offset, int length)
	{
		this.array = array;
		this.offset = offset;
		this.length = length;
	}	


	/**
		Value equality for byte arrays.
	*/
	public boolean equals(Object other) {
		if (other instanceof ByteArray) {
			ByteArray ob = (ByteArray) other;
			return ByteArray.equals(array, offset, length, ob.array, ob.offset, ob.length);
		}
		return false;
	}



	/**
	*/
	public int hashCode() {

		byte[] larray = array;

		int hash = length;
		for (int i = 0; i < length; i++) {
			hash += larray[i + offset];
		}
		return hash;
	}

	public final byte[] getArray() {
		return array;
	}
	public final int getOffset() {
		return offset;
	}

	public final int getLength() {
		return length;
	}
	public final void setLength(int newLength) {
		length = newLength;
	}
	
	/**
	 * Read this object from a stream of stored objects.
	 *
	 * @param in read this.
	 *
	 * @exception IOException					thrown on error
	 */
	public void readExternal( ObjectInput in ) throws IOException
	{
		int len = length = in.readInt();
		offset = 0; 
		array = new byte[len];

		in.readFully(array, 0, len);
	}


	/**
	 * Write the byte array out w/o compression
	 *
	 * @param out write bytes here.
	 *
	 * @exception IOException		thrown on error
	 */
	public void writeExternal(ObjectOutput out) throws IOException
	{
		out.writeInt(length);
		out.write(array, offset, length);
	}



	/**
		Compare two byte arrays using value equality.
		Two byte arrays are equal if their length is
		identical and their contents are identical.
	*/
	private static boolean equals(byte[] a, int aOffset, int aLength, byte[] b, int bOffset, int bLength) {

		if (aLength != bLength)
			return false;

		for (int i = 0; i < aLength; i++) {
			if (a[i + aOffset] != b[i + bOffset])
				return false;
		}
		return true;
	}
}