fromnetasciioutputstream.java

来自「apache推出的net包」· Java 代码 · 共 169 行

/*
 * Copyright 2001-2005 The Apache Software Foundation
 *
 * 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.
 */
package org.apache.commons.net.io;

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

/***
 * This class wraps an output stream, replacing all occurrences
 * of <CR><LF> (carriage return followed by a linefeed),
 * which is the NETASCII standard for representing a newline, with the
 * local line separator representation.  You would use this class to
 * implement ASCII file transfers requiring conversion from NETASCII.
 * <p>
 * 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 {@link #close  close() }, however, will
 * flush the carriage return.
 * <p>
 * <p>
 * @author Daniel F. Savarese
 ***/

public final class FromNetASCIIOutputStream extends FilterOutputStream
{
    private boolean __lastWasCR;

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


    private void __write(int ch) throws IOException
    {
        switch (ch)
        {
        case '\r':
            __lastWasCR = true;
            // Don't write anything.  We need to see if next one is linefeed
            break;
        case '\n':
            if (__lastWasCR)
            {
                out.write(FromNetASCIIInputStream._lineSeparatorBytes);
                __lastWasCR = false;
                break;
            }
            __lastWasCR = false;
            out.write('\n');
            break;
        default:
            if (__lastWasCR)
            {
                out.write('\r');
                __lastWasCR = false;
            }
            out.write(ch);
            break;
        }
    }


    /***
     * 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 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
     * completeness.
     * <p>
     * @param ch The byte to write.
     * @exception IOException If an error occurs while writing to the underlying
     *            stream.
     ***/
    public synchronized void write(int ch)
    throws IOException
    {
        if (FromNetASCIIInputStream._noConversionRequired)
        {
            out.write(ch);
            return ;
        }

        __write(ch);
    }


    /***
     * 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.
     ***/
    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.
     ***/
    public synchronized void write(byte buffer[], int offset, int length)
    throws IOException
    {
        if (FromNetASCIIInputStream._noConversionRequired)
        {
            // FilterOutputStream method is very slow.
            //super.write(buffer, offset, length);
            out.write(buffer, offset, length);
            return ;
        }

        while (length-- > 0)
            __write(buffer[offset++]);
    }


    /***
     * Closes the stream, writing all pending data.
     * <p>
     * @exception IOException  If an error occurs while closing the stream.
     ***/
    public synchronized void close()
    throws IOException
    {
        if (FromNetASCIIInputStream._noConversionRequired)
        {
            super.close();
            return ;
        }

        if (__lastWasCR)
            out.write('\r');
        super.close();
    }
}