base64outputstream.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/************************************************************************
 *
 * $Id: BASE64OutputStream.java,v 1.4 2005/12/13 21:24:47 bondolo Exp $
 *
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *********************************************************************************/

package net.jxta.impl.util;

import java.io.OutputStream;
import java.io.Writer;

import java.io.IOException;
import java.io.StringReader;
import java.io.ByteArrayOutputStream;
import java.io.StringWriter;

/**
 * An OutputStream implementation which encodes the written bytes into BASE64
 * encoded character data and writes the output to an associated text Writer.
 *
 * <p/>This implementation is not thread safe.
 *
 * @see net.jxta.impl.util.BASE64InputStream
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt" target="_blank">IETF RFC 2045 <i>MIME : Format of Internet Message Bodies</i></a>
 **/
public class BASE64OutputStream extends OutputStream {
    
    /**
     *  If <code>true</code> then the output stream has been closed.
     **/
    private boolean closed = false;
    
    /**
     *  The output writer.
     **/
    private Writer sendTo = null;
    
    /**
     *  Column width to breakup out.
     **/
    private final int columnWidth;
    
    /**
     *  Current output column.
     **/
    private int column = 0;
    
    /**
     *  Buffer for incomplete characters.
     **/
    private byte [] buffer = new byte[] { 0, 0, 0 };
    
    /**
     *  The number of characters currently in the buffer.
     **/
    private byte inBuffer = 0;
    
    /**
     * Construct a BASE64 Output Stream.
     *
     * @param sendTo The text Writer to which the BASE64 output will be
     * written.
     **/
    public BASE64OutputStream( Writer sendTo ) {
        this( sendTo, -1 );
    }
    
    /**
     * Construct a BASE64 Output Stream. The output will be broken into lines
     * <code>columnWidth</code> long.
     *
     * @param sendTo The text Writer to which the BASE64 output will be
     * written.
     * @param columnWidth The width of lines to break output into.
     **/
    public BASE64OutputStream( Writer sendTo, int columnWidth ) {
        this.sendTo = sendTo;
        this.columnWidth = columnWidth;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void write(int b) throws IOException {
        if( closed ) {
            throw new IOException( "OutputStream closed." );
        }
        
        buffer[ inBuffer++ ] = (byte) b;
        
        if( buffer.length == inBuffer ) {
            writeBuffer();
        }
    }
    
    /**
     *  {@inheritDoc}
     *
     *  <p/>The output writer is <b>NOT</b> closed.
     **/
    public void close() throws IOException {
        flush();
        
        closed = true;
        sendTo = null;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void flush() throws IOException {
        writeBuffer();
    }
    
    /**
     *  Write a full or partial buffer to the output writer.
     **/
    private void writeBuffer( ) throws IOException {
        if( 0 == inBuffer ) {
            return;
        }
        
        int val = ((buffer[0] & 0x00FF) << 16) +
        ((buffer[1] & 0x00FF) << 8) +
        (buffer[2] & 0x00FF);
        
        int c0 = (val >> 18) & 0x003F;
        int c1 = (val >> 12) & 0x003F;
        int c2 = (val >> 6) & 0x003F;
        int c3 = val & 0x003F;
        
        if( (columnWidth > 0) && (column > columnWidth) ) {
            sendTo.write( '\n' );
            column = 0;
        }
        
        sendTo.write( encodeSixBits(c0) );
        sendTo.write( encodeSixBits(c1) );
        
        if( inBuffer > 1  ) {
            sendTo.write( encodeSixBits(c2) );
        } else {
            sendTo.write( '=' );
        }
        
        if( inBuffer > 2 ) {
            sendTo.write( encodeSixBits(c3) );
        } else  {
            sendTo.write( '=' );
        }
        
        
        buffer[0] = 0; buffer[1] = 0; buffer[2] = 0;
        
        inBuffer = 0;
        column += 4;
    }
    
    /**
     *  BASE64 Encoding Table
     **/
    static final char encode [] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
        'w', 'x', 'y', 'z', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', '+', '/'
    };
    
    /**
     *  Encode six bits into a character using the standard BASE64 table.
     *
     *  @param b the bits to encode. b must be >=0 and <= 63
     *  @return the appropriate character for the input value.
     **/
    private static char encodeSixBits(int b) {
        char c;
        
        if( (b < 0) || (b > 63) )
            throw new IllegalArgumentException( "bad encode value" );
        else
            c = encode[b];
        
        return c;
    }
}