    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 *      https://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 */
    029public final class ToNetASCIIOutputStream extends FilterOutputStream {
    030    private boolean lastWasCR;
    031
    032    /**
    033     * Creates a ToNetASCIIOutputStream instance that wraps an existing OutputStream.
    034     *
    035     * @param output The OutputStream to wrap.
    036     */
    037    public ToNetASCIIOutputStream(final OutputStream output) {
    038        super(output);
    039        lastWasCR = false;
    040    }
    041
    042    /**
    043     * Writes a byte array to the stream.
    044     *
    045     * @param buffer The byte array to write.
    046     * @throws IOException If an error occurs while writing to the underlying stream.
    047     */
    048    @Override
    049    public synchronized void write(final byte buffer[]) throws IOException {
    050        write(buffer, 0, buffer.length);
    051    }
    052
    053    /**
    054     * Writes a number of bytes from a byte array to the stream starting from a given offset.
    055     *
    056     * @param buffer The byte array to write.
    057     * @param offset The offset into the array at which to start copying data.
    058     * @param length The number of bytes to write.
    059     * @throws IOException If an error occurs while writing to the underlying stream.
    060     */
    061    @Override
    062    public synchronized void write(final byte buffer[], int offset, int length) throws IOException {
    063        while (length-- > 0) {
    064            write(buffer[offset++]);
    065        }
    066    }
    067
    068    /**
    069     * 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
    070     * newlines to NETASCII line separators. This is transparent to the programmer and is only mentioned for completeness.
    071     *
    072     * @param ch The byte to write.
    073     * @throws IOException If an error occurs while writing to the underlying stream.
    074     */
    075    @Override
    076    public synchronized void write(final int ch) throws IOException {
    077        switch (ch) {
    078        case '\r':
    079            lastWasCR = true;
    080            out.write('\r');
    081            return;
    082        case '\n':
    083            if (!lastWasCR) {
    084                out.write('\r');
    085            }
    086            // falls through$
    087        default:
    088            lastWasCR = false;
    089            out.write(ch);
    090        }
    091    }
    092
    093}