base64.java

这是linux下ssl vpn的实现程序

/*
 *  SSL-Explorer
 *
 *  Copyright (C) 2003-2006 3SP LTD. All Rights Reserved
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2 of
 *  the License, or (at your option) any later version.
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
			
package com.sslexplorer.boot;

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

/**
 * Base 64 encoding / decoding utility class.
 * 
 * @author Lee David Painter <a href="mailto: [e-mail]">&lt;[e-mail]&gt;</a>
 * @version $Revision: 1.2 $
 */
public class Base64 {
    private static final byte[] encodingTable = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
                    (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O',
                    (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X',
                    (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
                    (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
                    (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
                    (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7',
                    (byte) '8', (byte) '9', (byte) '+', (byte) '/' };

    /**
     * encode the input data producing a base 64 encoded byte array.
     * 
     * @param data data to encode
     * @return a byte array containing the base 64 encoded data.
     */
    public static byte[] encode(byte[] data) {
        byte[] bytes;

        int modulus = data.length % 3;
        if (modulus == 0) {
            bytes = new byte[4 * data.length / 3];
        } else {
            bytes = new byte[4 * ((data.length / 3) + 1)];
        }

        int dataLength = (data.length - modulus);
        int a1, a2, a3;
        for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;

            bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
            bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
            bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
            bytes[j + 3] = encodingTable[a3 & 0x3f];
        }

        /*
         * process the tail end.
         */
        int b1, b2, b3;
        int d1, d2;

        switch (modulus) {
            case 0: /* nothing left to do */
                break;
            case 1:
                d1 = data[data.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = (d1 << 4) & 0x3f;

                bytes[bytes.length - 4] = encodingTable[b1];
                bytes[bytes.length - 3] = encodingTable[b2];
                bytes[bytes.length - 2] = (byte) '=';
                bytes[bytes.length - 1] = (byte) '=';
                break;
            case 2:
                d1 = data[data.length - 2] & 0xff;
                d2 = data[data.length - 1] & 0xff;

                b1 = (d1 >>> 2) & 0x3f;
                b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                b3 = (d2 << 2) & 0x3f;

                bytes[bytes.length - 4] = encodingTable[b1];
                bytes[bytes.length - 3] = encodingTable[b2];
                bytes[bytes.length - 2] = encodingTable[b3];
                bytes[bytes.length - 1] = (byte) '=';
                break;
        }

        return bytes;
    }

    /*
     * set up the decoding table.
     */
    private static final byte[] decodingTable;

    static {
        decodingTable = new byte[128];

        for (int i = 'A'; i <= 'Z'; i++) {
            decodingTable[i] = (byte) (i - 'A');
        }

        for (int i = 'a'; i <= 'z'; i++) {
            decodingTable[i] = (byte) (i - 'a' + 26);
        }

        for (int i = '0'; i <= '9'; i++) {
            decodingTable[i] = (byte) (i - '0' + 52);
        }

        decodingTable['+'] = 62;
        decodingTable['/'] = 63;
    }

    /**
     * decode the base 64 encoded input data. It is assumed the input data is
     * valid.
     * 
     * @param data data to decode
     * @return a byte array representing the decoded data.
     */
    public static byte[] decode(byte[] data) {
        byte[] bytes;
        byte b1, b2, b3, b4;

        if (data[data.length - 2] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
        } else if (data[data.length - 1] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((data.length / 4) * 3)];
        }

        for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3) {
            b1 = decodingTable[data[i]];
            b2 = decodingTable[data[i + 1]];
            b3 = decodingTable[data[i + 2]];
            b4 = decodingTable[data[i + 3]];

            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }

        if (data[data.length - 2] == '=') {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];

            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (data[data.length - 1] == '=') {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];
            b3 = decodingTable[data[data.length - 2]];

            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = decodingTable[data[data.length - 4]];
            b2 = decodingTable[data[data.length - 3]];
            b3 = decodingTable[data[data.length - 2]];
            b4 = decodingTable[data[data.length - 1]];

            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }

        return bytes;
    }

    private static boolean ignore(char c) {
        return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
    }

    /**
     * decode the base 64 encoded String data - whitespace will be ignored.
     * 
     * @param data data to decod
     * @return a byte array representing the decoded data.
     */
    public static byte[] decode(String data) {
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();

        try {
            decode(data, bOut);
        } catch (IOException e) {
            throw new RuntimeException("exception decoding base64 string: " + e);
        }

        return bOut.toByteArray();
    }

    /**
     * decode the base 64 encoded String data writing it to the given output
     * stream, whitespace characters will be ignored.
     * 
     * @param data data to decode
     * @param out output stream to write to
     * @return the number of bytes produced.
     * @throws IOException
     */
    public static int decode(String data, OutputStream out) throws IOException {
        byte b1, b2, b3, b4;
        int length = 0;

        int end = data.length();

        while (end > 0) {
            if (!ignore(data.charAt(end - 1))) {
                break;
            }

            end--;
        }

        for (int i = 0; i < end - 4; i += 4) {
            if (ignore(data.charAt(i))) {
                continue;
            }

            b1 = decodingTable[data.charAt(i)];
            b2 = decodingTable[data.charAt(i + 1)];
            b3 = decodingTable[data.charAt(i + 2)];
            b4 = decodingTable[data.charAt(i + 3)];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            length += 3;
        }

        if (data.charAt(end - 2) == '=') {
            b1 = decodingTable[data.charAt(end - 4)];
            b2 = decodingTable[data.charAt(end - 3)];

            out.write((b1 << 2) | (b2 >> 4));

            length += 1;
        } else if (data.charAt(end - 1) == '=') {
            b1 = decodingTable[data.charAt(end - 4)];
            b2 = decodingTable[data.charAt(end - 3)];
            b3 = decodingTable[data.charAt(end - 2)];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));

            length += 2;
        } else {
            b1 = decodingTable[data.charAt(end - 4)];
            b2 = decodingTable[data.charAt(end - 3)];
            b3 = decodingTable[data.charAt(end - 2)];
            b4 = decodingTable[data.charAt(end - 1)];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            length += 3;
        }

        return length;
    }
}