FromNetASCIIOutputStream.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 occurrences of
 * <CR><LF> (carriage return followed by a linefeed), which is the
 * NETASCII standard for representing a newline, with the local line separator
 * representation. You would use this class to implement ASCII file transfers
 * requiring conversion from NETASCII.
 * <p>
 * Because of the translation process, a call to <code>flush()</code> will not
 * flush the last byte written if that byte was a carriage return. A call to
 * {@link #close close() }, however, will flush the carriage return.
 * <p>
 * <p>
 ***/

public final class FromNetASCIIOutputStream extends FilterOutputStream {
	private boolean __lastWasCR;

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

	private void __write(int ch) throws IOException {
		switch (ch) {
		case '\r':
			__lastWasCR = true;
			// Don't write anything. We need to see if next one is linefeed
			break;
		case '\n':
			if (__lastWasCR) {
				out.write(FromNetASCIIInputStream._lineSeparatorBytes);
				__lastWasCR = false;
				break;
			}
			__lastWasCR = false;
			out.write('\n');
			break;
		default:
			if (__lastWasCR) {
				out.write('\r');
				__lastWasCR = false;
			}
			out.write(ch);
			break;
		}
	}

	/***
	 * Writes a byte to the stream. Note that a call to this method might not
	 * actually write a byte to the underlying stream until a subsequent
	 * character is written, from which it can be determined if a NETASCII line
	 * separator was encountered. 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 {
		if (FromNetASCIIInputStream._noConversionRequired) {
			out.write(ch);
			return;
		}

		__write(ch);
	}

	/***
	 * 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 {
		if (FromNetASCIIInputStream._noConversionRequired) {
			// FilterOutputStream method is very slow.
			// super.write(buffer, offset, length);
			out.write(buffer, offset, length);
			return;
		}

		while (length-- > 0) {
			__write(buffer[offset++]);
		}
	}

	/***
	 * Closes the stream, writing all pending data.
	 * <p>
	 * 
	 * @exception IOException
	 *                If an error occurs while closing the stream.
	 ***/
	@Override
	public synchronized void close() throws IOException {
		if (FromNetASCIIInputStream._noConversionRequired) {
			super.close();
			return;
		}

		if (__lastWasCR) {
			out.write('\r');
		}
		super.close();
	}
}