/*

   Derby - Class org.apache.derby.iapi.services.io.ArrayUtil

   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.derby.iapi.services.io;

import java.io.ObjectOutput;
import java.io.ObjectInput;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
  Utility class for constructing and reading and writing arrays from/to
  formatId streams and for performing other operations on arrays.
 
  @version 0.1
 */
public abstract class ArrayUtil
{
	///////////////////////////////////////////////////////////////////
	//
	// Methods to copy arrays.
	//
	///////////////////////////////////////////////////////////////////

    /** Copy an array of objects; the original array could be null */
    public  static  T[] copy( T[] original )
    {
        return (original == null) ?
                null :
                Arrays.copyOf(original, original.length);
    }

    /** Copy a (possibly null) array of booleans */
    public  static  boolean[]   copy( boolean[] original )
    {
        return (original == null) ? null : (boolean[]) original.clone();
    }

    /** Copy a (possibly null) array of bytes */
    public  static  byte[]   copy( byte[] original )
    {
        return (original == null) ? null : (byte[]) original.clone();
    }

    /** Copy a (possibly null) array of ints */
    public  static  int[]   copy( int[] original )
    {
        return (original == null) ? null : (int[]) original.clone();
    }

    /** Copy a (possibly null) array of longs */
    public  static  long[]   copy( long[] original )
    {
        return (original == null) ? null : (long[]) original.clone();
    }

    /** Copy a (possibly null) 2-dimensional array of ints */
    public  static  int[][]   copy2( int[][] original )
    {
        if ( original == null ) { return null; }

        int[][] result = new int[ original.length ][];
        for ( int i = 0; i < original.length; i++ )
        {
            result[ i ] = copy( original[ i ] );
        }
        
        return result;
    }

    /**
     * Make the contents of an array available as a read-only list. If the
     * array is null, an empty list will be returned.
     */
    public static  List asReadOnlyList(T... array) {
        if (array == null) {
            return Collections.emptyList();
        } else {
            return Collections.unmodifiableList(Arrays.asList(array));
        }
    }

	///////////////////////////////////////////////////////////////////
	//
	// Methods for Arrays of OBJECTS.  Cannot be used for an
	// array of primitives, see below for something for primitives
	//
	///////////////////////////////////////////////////////////////////
	/**
	  Write the length of an array of objects to an output stream.

	  The length

	  @param	out		ObjectOutput stream
	  @param	a		array of objects whose length should be written.

	  @exception java.io.IOException The write caused an IOException. 
	  */
	public static void writeArrayLength(ObjectOutput out, Object[] a)
		 throws IOException
	{
		out.writeInt(a.length);
	}

	/**
	  Write an array of objects to an output stream.

	  @param	out		Object output stream to write to.
	  @param	a		array of objects to write.

	  @exception java.io.IOException The write caused an IOException. 
	  */
	public static void writeArrayItems(ObjectOutput out, Object[] a)
		 throws IOException
	{
		if (a == null)
			return;

		for(int ix = 0; ix < a.length; ix++)
		{	out.writeObject(a[ix]); }
	}

	/**
	  Write an array of objects and length to an output stream.
	  Does equivalent of writeArrayLength() followed by writeArrayItems()

	  @param	out		Object output stream to write to.
	  @param	a		array of objects to write.

	  @exception java.io.IOException The write caused an IOException. 
	  */
	public static void writeArray(ObjectOutput out, Object[] a)
		 throws IOException
	{
		if (a == null) 
		{
			out.writeInt(0);
			return;
		}

		out.writeInt(a.length);
		for(int ix = 0; ix < a.length; ix++)
		{	out.writeObject(a[ix]); }
	}

	/**
	  Read an array of objects out of a stream.

	  @param	in	Input stream
	  @param	a	array to read into

	  @exception java.io.IOException The write caused an IOException. 
	  @exception java.lang.ClassNotFoundException The Class for an Object we are reading does not exist
	  */
	public static void readArrayItems(ObjectInput in, Object[] a)
		 throws IOException, ClassNotFoundException
	{
		for (int ix=0; ix 0) {
            stringArray = new String[size];
            readArrayItems(in, stringArray);
        }

		return stringArray;
	}
	
	///////////////////////////////////////////////////////////////////
	//
	// Methods for Arrays of BOOLEANS
	//
	///////////////////////////////////////////////////////////////////

	/**
	  Write an array of booleans to an ObjectOutput. This writes the array
	  in a format readBooleanArray understands.

	  @param out the ObjectOutput.
	  @param a the array.
	  @exception java.io.IOException The write caused an IOException. 
	  */
	public static void writeBooleanArray(ObjectOutput out, boolean[] a) throws IOException {
		if (a == null)
			out.writeInt(0);
		else {
			out.writeInt(a.length);
			for (int i=0; i