ToNetASCIIOutputStream.java

/*
 * 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 com.myjavaworld.ftp;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/***
 * This class wraps an output stream, replacing all singly occurring <LF>
 * (linefeed) characters with <CR><LF> (carriage return followed by
 * linefeed), which is the NETASCII standard for representing a newline. You
 * would use this class to implement ASCII file transfers requiring conversion
 * to NETASCII.
 * <p>
 * <p>
 ***/

public final class ToNetASCIIOutputStream extends FilterOutputStream {
	private boolean __lastWasCR;

	/***
	 * Creates a ToNetASCIIOutputStream instance that wraps an existing
	 * OutputStream.
	 * <p>
	 * 
	 * @param output
	 *            The OutputStream to wrap.
	 ***/
	public ToNetASCIIOutputStream(OutputStream output) {
		super(output);
		__lastWasCR = false;
	}

	/***
	 * Writes a byte to the stream. Note that a call to this method may result
	 * in multiple writes to the underlying input stream in order to convert
	 * naked newlines to NETASCII line separators. This is transparent to the
	 * programmer and is only mentioned for completeness.
	 * <p>
	 * 
	 * @param ch
	 *            The byte to write.
	 * @exception IOException
	 *                If an error occurs while writing to the underlying stream.
	 ***/
	@Override
	public synchronized void write(int ch) throws IOException {
		switch (ch) {
		case '\r':
			__lastWasCR = true;
			out.write('\r');
			return;
		case '\n':
			if (!__lastWasCR) {
				out.write('\r');
			}
			//$FALL-THROUGH$
		default:
			__lastWasCR = false;
			out.write(ch);
			return;
		}
	}

	/***
	 * Writes a byte array to the stream.
	 * <p>
	 * 
	 * @param buffer
	 *            The byte array to write.
	 * @exception IOException
	 *                If an error occurs while writing to the underlying stream.
	 ***/
	@Override
	public synchronized void write(byte buffer[]) throws IOException {
		write(buffer, 0, buffer.length);
	}

	/***
	 * Writes a number of bytes from a byte array to the stream starting from a
	 * given offset.
	 * <p>
	 * 
	 * @param buffer
	 *            The byte array to write.
	 * @param offset
	 *            The offset into the array at which to start copying data.
	 * @param length
	 *            The number of bytes to write.
	 * @exception IOException
	 *                If an error occurs while writing to the underlying stream.
	 ***/
	@Override
	public synchronized void write(byte buffer[], int offset, int length)
			throws IOException {
		while (length-- > 0) {
			write(buffer[offset++]);
		}
	}

}