    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 &lt;LF&gt; (linefeed) characters with &lt;CR&gt;&lt;LF&gt; (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}