    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 occurrences of &lt;CR&gt;&lt;LF&gt; (carriage return followed by a linefeed), which is the NETASCII standard
    026 * for representing a newline, with the local line separator representation. You would use this class to implement ASCII file transfers requiring conversion
    027 * from NETASCII.
    028 * <p>
    029 * Because of the translation process, a call to <code>flush()</code> will not flush the last byte written if that byte was a carriage return. A call to
    030 * {@link #close close() }, however, will flush the carriage return.
    031 *
    032 *
    033 */
    034
    035public final class FromNetASCIIOutputStream extends FilterOutputStream {
    036    private boolean lastWasCR;
    037
    038    /**
    039     * Creates a FromNetASCIIOutputStream instance that wraps an existing OutputStream.
    040     *
    041     * @param output The OutputStream to wrap.
    042     */
    043    public FromNetASCIIOutputStream(final OutputStream output) {
    044        super(output);
    045        lastWasCR = false;
    046    }
    047
    048    /**
    049     * Closes the stream, writing all pending data.
    050     *
    051     * @throws IOException If an error occurs while closing the stream.
    052     */
    053    @Override
    054    public synchronized void close() throws IOException {
    055        if (FromNetASCIIInputStream._noConversionRequired) {
    056            super.close();
    057            return;
    058        }
    059
    060        if (lastWasCR) {
    061            out.write('\r');
    062        }
    063        super.close();
    064    }
    065
    066    /**
    067     * Writes a byte array to the stream.
    068     *
    069     * @param buffer The byte array to write.
    070     * @throws IOException If an error occurs while writing to the underlying stream.
    071     */
    072    @Override
    073    public synchronized void write(final byte buffer[]) throws IOException {
    074        write(buffer, 0, buffer.length);
    075    }
    076
    077    /**
    078     * Writes a number of bytes from a byte array to the stream starting from a given offset.
    079     *
    080     * @param buffer The byte array to write.
    081     * @param offset The offset into the array at which to start copying data.
    082     * @param length The number of bytes to write.
    083     * @throws IOException If an error occurs while writing to the underlying stream.
    084     */
    085    @Override
    086    public synchronized void write(final byte buffer[], int offset, int length) throws IOException {
    087        if (FromNetASCIIInputStream._noConversionRequired) {
    088            // FilterOutputStream method is very slow.
    089            // super.write(buffer, offset, length);
    090            out.write(buffer, offset, length);
    091            return;
    092        }
    093
    094        while (length-- > 0) {
    095            writeInt(buffer[offset++]);
    096        }
    097    }
    098
    099    /**
    100     * Writes a byte to the stream. Note that a call to this method might not actually write a byte to the underlying stream until a subsequent character is
    101     * written, from which it can be determined if a NETASCII line separator was encountered. This is transparent to the programmer and is only mentioned for
    102     * completeness.
    103     *
    104     * @param ch The byte to write.
    105     * @throws IOException If an error occurs while writing to the underlying stream.
    106     */
    107    @Override
    108    public synchronized void write(final int ch) throws IOException {
    109        if (FromNetASCIIInputStream._noConversionRequired) {
    110            out.write(ch);
    111            return;
    112        }
    113
    114        writeInt(ch);
    115    }
    116
    117    private void writeInt(final int ch) throws IOException {
    118        switch (ch) {
    119        case '\r':
    120            lastWasCR = true;
    121            // Don't write anything. We need to see if next one is linefeed
    122            break;
    123        case '\n':
    124            if (lastWasCR) {
    125                out.write(FromNetASCIIInputStream._lineSeparatorBytes);
    126                lastWasCR = false;
    127                break;
    128            }
    129            out.write('\n');
    130            break;
    131        default:
    132            if (lastWasCR) {
    133                out.write('\r');
    134                lastWasCR = false;
    135            }
    136            out.write(ch);
    137            break;
    138        }
    139    }
    140}