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