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The TwelveMonkeys Core library. Contains common utility classes.
There is a newer version: 2.3
/*
 * Copyright (c) 2008, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name "TwelveMonkeys" nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS 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 THE COPYRIGHT OWNER OR
 * 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.
 */

package com.twelvemonkeys.io.enc;

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

/**
 * {@code Encoder} implementation for standard base64 encoding.
 * 
 * @see RFC 1421
 * @see 
 *
 * @see Base64Decoder
 *
 * @author Harald Kuhr
 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/enc/Base64Encoder.java#2 $
 */
public class Base64Encoder implements Encoder {

    public void encode(final OutputStream pStream, final byte[] pBuffer, final int pOffset, final int pLength) 
            throws IOException
    {
        if (pOffset < 0 || pOffset > pLength || pOffset > pBuffer.length) {
            throw new IndexOutOfBoundsException("offset outside [0...length]");
        }
        else if (pLength > pBuffer.length) {
            throw new IndexOutOfBoundsException("length > buffer length");
        }

        // TODO: Implement
        // NOTE: This is impossible, given the current spec, as we need to either:
        //  - buffer all data in the EncoderStream
        //  - or have flush/end method(s) in the Encoder
        // to ensure proper end of stream handling

        int length;
        int offset = pOffset;

        // TODO: Temp impl, will only work for single writes
        while ((pBuffer.length - offset) > 0) {
            byte a, b, c;

            if ((pBuffer.length - offset) > 2) {
                length = 3;
            }
            else {
                length = pBuffer.length - offset;
            }

            switch (length) {
                case 1:
                    a = pBuffer[offset];
                    b = 0;
                    pStream.write(Base64Decoder.PEM_ARRAY[(a >>> 2) & 0x3F]);
                    pStream.write(Base64Decoder.PEM_ARRAY[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                    pStream.write('=');
                    pStream.write('=');
                    offset++;
                    break;
                case 2:
                    a = pBuffer[offset];
                    b = pBuffer[offset + 1];
                    c = 0;
                    pStream.write(Base64Decoder.PEM_ARRAY[(a >>> 2) & 0x3F]);
                    pStream.write(Base64Decoder.PEM_ARRAY[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                    pStream.write(Base64Decoder.PEM_ARRAY[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
                    pStream.write('=');
                    offset += offset + 2; // ???
                    break;
                default:
                    a = pBuffer[offset];
                    b = pBuffer[offset + 1];
                    c = pBuffer[offset + 2];
                    pStream.write(Base64Decoder.PEM_ARRAY[(a >>> 2) & 0x3F]);
                    pStream.write(Base64Decoder.PEM_ARRAY[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                    pStream.write(Base64Decoder.PEM_ARRAY[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
                    pStream.write(Base64Decoder.PEM_ARRAY[c & 0x3F]);
                    offset = offset + 3;
                    break;
            }
        }
    }
}