FromNetASCIIOutputStream.java

package ch.cyberduck.core.io;

/*
 * Copyright 2001-2005 The Apache Software Foundation
 *
 * 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.
 */

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 <a href="#close"> close() </a>, however, will
 * flush the carriage return.
 * <p/>
 * <p/>
 *
 * @author Daniel F. Savarese
 *         *
 */

public final class FromNetASCIIOutputStream extends FilterOutputStream {
	/**
	 * @uml.property  name="__lastWasCR"
	 */
	private boolean __lastWasCR;

	/**
	 * @uml.property  name="_noConversionRequired"
	 */
	private boolean _noConversionRequired;
	/**
	 * @uml.property  name="_lineSeparator"
	 */
	private String _lineSeparator;
	/**
	 * @uml.property  name="_lineSeparatorBytes" multiplicity="(0 -1)" dimension="1"
	 */
	private byte[] _lineSeparatorBytes;

	/**
	 * Creates a FromNetASCIIOutputStream instance that wraps an existing
	 * OutputStream.
	 * <p/>
	 *
	 * @param output The OutputStream to wrap.
	 *               *
	 */
	public FromNetASCIIOutputStream(OutputStream output, String lineSeparator) {
		super(output);
		_lineSeparator = lineSeparator;
		_lineSeparatorBytes = lineSeparator.getBytes();
		_noConversionRequired = lineSeparator.equals("\r\n");
		__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(_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.
	 * @throws IOException If an error occurs while writing to the underlying
	 *                     stream.
	 *                     *
	 */
	public synchronized void write(int ch)
	    throws IOException {
		if(_noConversionRequired) {
			out.write(ch);
			return;
		}

		__write(ch);
	}


	/**
	 * Writes a byte array to the stream.
	 * <p/>
	 *
	 * @param buffer The byte array to write.
	 * @throws IOException If an error occurs while writing to the underlying
	 *                     stream.
	 *                     *
	 */
	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.
	 * @throws IOException If an error occurs while writing to the underlying
	 *                     stream.
	 *                     *
	 */
	public synchronized void write(byte buffer[], int offset, int length)
	    throws IOException {
		if(_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/>
	 *
	 * @throws IOException If an error occurs while closing the stream.
	 *                     *
	 */
	public synchronized void close()
	    throws IOException {
		if(_noConversionRequired) {
			super.close();
			return;
		}

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