ReaderUTF16.java

/*
 * Copyright  1990-2009 Sun Microsystems, Inc. All Rights Reserved. 
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER 
 *  
 * This program is free software; you can redistribute it and/or 
 * modify it under the terms of the GNU General Public License version 
 * 2 only, as published by the Free Software Foundation. 
 *  
 * This program 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 version 2 for more details (a copy is 
 * included at /legal/license.txt). 
 *  
 * You should have received a copy of the GNU General Public License 
 * version 2 along with this work; if not, write to the Free Software 
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 
 * 02110-1301 USA 
 *  
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa 
 * Clara, CA 95054 or visit www.sun.com if you need additional 
 * information or have any questions.
 */

package com.sun.ukit.io;

import java.io.Reader;
import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;

/**
 * UTF-16 encoded stream reader.
 */
public class ReaderUTF16 extends Reader
{
	final private InputStream	is;
	final private char			bo;
	final private byte[]		buff = new byte[128];

	/**
	 * Constructor.
	 *
	 * Byte order argument can be: 'l' for little-endian or 'b' for big-endian.
	 *
	 * @param is A byte input stream.
	 * @param bo A byte order in the input stream. 
	 */
	public ReaderUTF16(InputStream is, char bo)
	{
		switch (bo) {
		case 'l': case 'b': 
			break;
		default:
			throw new IllegalArgumentException();
		}
		this.bo = bo;
		this.is = is;
	}

	/**
	 * Reads characters into a portion of an array.
	 *
	 * @param cbuf Destination buffer.
	 * @param off Offset at which to start storing characters.
	 * @param len Maximum number of characters to read.
	 * @exception IOException If any IO errors occur.
	 */
	public int read(char[] cbuf, int off, int len) throws IOException
	{
		int num = 0;
		int bcnt;

		if (bo == 'b') {
			while (num < len) {
				if( (bcnt = is.read(buff, 0, Math.min(buff.length, (len - num) * 2))) < 0 )
					return (num != 0)? num: -1;
				if( (bcnt & 1) != 0 )
					throw new EOFException();
				bcnt >>= 1;
				num += bcnt;
				for( int bidx = 0; bcnt-- > 0;){
					cbuf[off++] = (char)((buff[bidx++] << 8) | (buff[bidx++] & 0xff));
				}
			}
		} else {
			while (num < len) {
				if( (bcnt = is.read(buff, 0, Math.min(buff.length, (len - num) * 2))) < 0 )
					return (num != 0)? num: -1;
				if( (bcnt & 1) != 0 )
					throw new EOFException();
				bcnt >>= 1;
				num += bcnt;
				for( int bidx = 0; bcnt-- > 0;){
					cbuf[off++] = (char)((buff[bidx++] & 0xff) | (buff[bidx++] << 8));
				}
			}
		}
		return num;
	}

	/**
	 * Reads a single character.
	 *
	 * @return The character read, as an integer in the range 0 to 65535 
	 *	(0x0000-0xffff), or -1 if the end of the stream has been reached.
	 * @exception IOException If any IO errors occur.
	 */
	public int read() throws IOException
	{
		switch( is.read(buff, 0, 2) ){
			case 1:
				throw new EOFException();
			case 2:
				break;
			default:
				return -1;
		}
		
		if (bo == 'b')
			return (char)((buff[0] << 8) | (buff[1] & 0xff));
		return (char)((buff[1] << 8) | (buff[0] & 0xff));
	}

	/**
	 * Closes the stream.
	 *
	 * @exception IOException If any IO errors occur.
	 */
	public void close()
		throws IOException
	{
		is.close();
	}
}