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
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}