ToNetASCIIOutputStream.java

/*
 * Copyright 2010 netling project <http://netling.org>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file may incorporate work covered by the following copyright and
 * permission notice:
 *
 *     Licensed to the Apache Software Foundation (ASF) under one
 *     or more contributor license agreements.  See the NOTICE file
 *     distributed with this work for additional information
 *     regarding copyright ownership.  The ASF licenses this file
 *     to you under the Apache License, Version 2.0 (the
 *     "License"); you may not use this file except in compliance
 *     with the License.  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *      Unless required by applicable law or agreed to in writing,
 *      software distributed under the License is distributed on an
 *      "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *      KIND, either express or implied.  See the License for the
 *      specific language governing permissions and limitations
 *      under the License.
 */
package org.netling.io;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/***
 * This class wraps an output stream, replacing all singly occurring
 * <LF> (linefeed) characters with <CR><LF> (carriage return
 * followed by linefeed), which is the NETASCII standard for representing
 * a newline.
 * You would use this class to implement ASCII file transfers requiring
 * conversion to NETASCII.
 ***/

public final class ToNetASCIIOutputStream extends FilterOutputStream
{
    private boolean lastWasCR;

    /***
     * Creates a ToNetASCIIOutputStream instance that wraps an existing
     * OutputStream.
     * <p>
     * @param output  The OutputStream to wrap.
     ***/
    public ToNetASCIIOutputStream(OutputStream output)
    {
        super(output);
        lastWasCR = false;
    }


    /***
     * 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 newlines to NETASCII line separators.
     * This is transparent to the programmer and is only mentioned for
     * completeness.
     * <p>
     * @param ch The byte to write.
     * @exception IOException If an error occurs while writing to the underlying
     *            stream.
     ***/
    @Override
    public synchronized void write(int ch)
    throws IOException
    {
        switch (ch)
        {
        case '\r':
            lastWasCR = true;
            out.write('\r');
            return ;
        case '\n':
            if (!lastWasCR)
                out.write('\r');
            //$FALL-THROUGH$
        default:
            lastWasCR = false;
            out.write(ch);
            return ;
        }
    }


    /***
     * Writes a byte array to the stream.
     * <p>
     * @param buffer  The byte array to write.
     * @exception IOException If an error occurs while writing to the underlying
     *            stream.
     ***/
    @Override
    public synchronized void write(byte buffer[])
    throws IOException
    {
        write(buffer, 0, buffer.length);
    }


    /***
     * Writes a number of bytes from a byte array to the stream starting from
     * a given offset.
     * <p>
     * @param buffer  The byte array to write.
     * @param offset  The offset into the array at which to start copying data.
     * @param length  The number of bytes to write.
     * @exception IOException If an error occurs while writing to the underlying
     *            stream.
     ***/
    @Override
    public synchronized void write(byte buffer[], int offset, int length)
    throws IOException
    {
        while (length-- > 0)
            write(buffer[offset++]);
    }

}