001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.io;
019
020import java.io.FilterOutputStream;
021import java.io.IOException;
022import java.io.OutputStream;
023
024/**
025 * This class wraps an output stream, replacing all singly occurring <LF> (linefeed) characters with <CR><LF> (carriage return followed by
026 * linefeed), which is the NETASCII standard for representing a newline. You would use this class to implement ASCII file transfers requiring conversion to
027 * NETASCII.
028 *
029 *
030 */
031
032public final class ToNetASCIIOutputStream extends FilterOutputStream {
033    private boolean lastWasCR;
034
035    /**
036     * Creates a ToNetASCIIOutputStream instance that wraps an existing OutputStream.
037     *
038     * @param output The OutputStream to wrap.
039     */
040    public ToNetASCIIOutputStream(final OutputStream output) {
041        super(output);
042        lastWasCR = false;
043    }
044
045    /**
046     * Writes a byte array to the stream.
047     *
048     * @param buffer The byte array to write.
049     * @throws IOException If an error occurs while writing to the underlying stream.
050     */
051    @Override
052    public synchronized void write(final byte buffer[]) throws IOException {
053        write(buffer, 0, buffer.length);
054    }
055
056    /**
057     * Writes a number of bytes from a byte array to the stream starting from a given offset.
058     *
059     * @param buffer The byte array to write.
060     * @param offset The offset into the array at which to start copying data.
061     * @param length The number of bytes to write.
062     * @throws IOException If an error occurs while writing to the underlying stream.
063     */
064    @Override
065    public synchronized void write(final byte buffer[], int offset, int length) throws IOException {
066        while (length-- > 0) {
067            write(buffer[offset++]);
068        }
069    }
070
071    /**
072     * 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
073     * newlines to NETASCII line separators. This is transparent to the programmer and is only mentioned for completeness.
074     *
075     * @param ch The byte to write.
076     * @throws IOException If an error occurs while writing to the underlying stream.
077     */
078    @Override
079    public synchronized void write(final int ch) throws IOException {
080        switch (ch) {
081        case '\r':
082            lastWasCR = true;
083            out.write('\r');
084            return;
085        case '\n':
086            if (!lastWasCR) {
087                out.write('\r');
088            }
089            //$FALL-THROUGH$
090        default:
091            lastWasCR = false;
092            out.write(ch);
093        }
094    }
095
096}