    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
    033public final class FromNetASCIIOutputStream extends FilterOutputStream {
    034    private boolean lastWasCR;
    035
    036    /**
    037     * Creates a FromNetASCIIOutputStream instance that wraps an existing OutputStream.
    038     *
    039     * @param output The OutputStream to wrap.
    040     */
    041    public FromNetASCIIOutputStream(final OutputStream output) {
    042        super(output);
    043        lastWasCR = false;
    044    }
    045
    046    /**
    047     * Closes the stream, writing all pending data.
    048     *
    049     * @throws IOException If an error occurs while closing the stream.
    050     */
    051    @Override
    052    public synchronized void close() throws IOException {
    053        if (FromNetASCIIInputStream._noConversionRequired) {
    054            super.close();
    055            return;
    056        }
    057
    058        if (lastWasCR) {
    059            out.write('\r');
    060        }
    061        super.close();
    062    }
    063
    064    /**
    065     * Writes a byte array to the stream.
    066     *
    067     * @param buffer The byte array to write.
    068     * @throws IOException If an error occurs while writing to the underlying stream.
    069     */
    070    @Override
    071    public synchronized void write(final byte buffer[]) throws IOException {
    072        write(buffer, 0, buffer.length);
    073    }
    074
    075    /**
    076     * Writes a number of bytes from a byte array to the stream starting from a given offset.
    077     *
    078     * @param buffer The byte array to write.
    079     * @param offset The offset into the array at which to start copying data.
    080     * @param length The number of bytes to write.
    081     * @throws IOException If an error occurs while writing to the underlying stream.
    082     */
    083    @Override
    084    public synchronized void write(final byte buffer[], int offset, int length) throws IOException {
    085        if (FromNetASCIIInputStream._noConversionRequired) {
    086            // FilterOutputStream method is very slow.
    087            // super.write(buffer, offset, length);
    088            out.write(buffer, offset, length);
    089            return;
    090        }
    091
    092        while (length-- > 0) {
    093            writeInt(buffer[offset++]);
    094        }
    095    }
    096
    097    /**
    098     * 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
    099     * 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
    100     * completeness.
    101     *
    102     * @param ch The byte to write.
    103     * @throws IOException If an error occurs while writing to the underlying stream.
    104     */
    105    @Override
    106    public synchronized void write(final int ch) throws IOException {
    107        if (FromNetASCIIInputStream._noConversionRequired) {
    108            out.write(ch);
    109            return;
    110        }
    111
    112        writeInt(ch);
    113    }
    114
    115    private void writeInt(final int ch) throws IOException {
    116        switch (ch) {
    117        case '\r':
    118            lastWasCR = true;
    119            // Don't write anything. We need to see if next one is linefeed
    120            break;
    121        case '\n':
    122            if (lastWasCR) {
    123                out.write(FromNetASCIIInputStream._lineSeparatorBytes);
    124                lastWasCR = false;
    125                break;
    126            }
    127            out.write('\n');
    128            break;
    129        default:
    130            if (lastWasCR) {
    131                out.write('\r');
    132                lastWasCR = false;
    133            }
    134            out.write(ch);
    135            break;
    136        }
    137    }
    138}