    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
    030public final class ToNetASCIIOutputStream extends FilterOutputStream {
    031    private boolean lastWasCR;
    032
    033    /**
    034     * Creates a ToNetASCIIOutputStream instance that wraps an existing OutputStream.
    035     *
    036     * @param output The OutputStream to wrap.
    037     */
    038    public ToNetASCIIOutputStream(final OutputStream output) {
    039        super(output);
    040        lastWasCR = false;
    041    }
    042
    043    /**
    044     * Writes a byte array to the stream.
    045     *
    046     * @param buffer The byte array to write.
    047     * @throws IOException If an error occurs while writing to the underlying stream.
    048     */
    049    @Override
    050    public synchronized void write(final byte buffer[]) throws IOException {
    051        write(buffer, 0, buffer.length);
    052    }
    053
    054    /**
    055     * Writes a number of bytes from a byte array to the stream starting from a given offset.
    056     *
    057     * @param buffer The byte array to write.
    058     * @param offset The offset into the array at which to start copying data.
    059     * @param length The number of bytes to write.
    060     * @throws IOException If an error occurs while writing to the underlying stream.
    061     */
    062    @Override
    063    public synchronized void write(final byte buffer[], int offset, int length) throws IOException {
    064        while (length-- > 0) {
    065            write(buffer[offset++]);
    066        }
    067    }
    068
    069    /**
    070     * 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
    071     * newlines to NETASCII line separators. This is transparent to the programmer and is only mentioned for completeness.
    072     *
    073     * @param ch The byte to write.
    074     * @throws IOException If an error occurs while writing to the underlying stream.
    075     */
    076    @Override
    077    public synchronized void write(final int ch) throws IOException {
    078        switch (ch) {
    079        case '\r':
    080            lastWasCR = true;
    081            out.write('\r');
    082            return;
    083        case '\n':
    084            if (!lastWasCR) {
    085                out.write('\r');
    086            }
    087            //$FALL-THROUGH$
    088        default:
    089            lastWasCR = false;
    090            out.write(ch);
    091        }
    092    }
    093
    094}