base64.java

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/* Copyright (c) 2002,2003, Stefan Haustein, Oberhausen, Rhld., Germany
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The  above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE. */
 
 
package org.kobjects.base64;

import java.io.*;

public class Base64 {

    static final char[] charTab =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
            .toCharArray();

    public static String encode(byte[] data) {
        return encode(data, 0, data.length, null).toString();
    }

    /** Encodes the part of the given byte array denoted by start and
    len to the Base64 format.  The encoded data is appended to the
    given StringBuffer. If no StringBuffer is given, a new one is
    created automatically. The StringBuffer is the return value of
    this method. */

    public static StringBuffer encode(
        byte[] data,
        int start,
        int len,
        StringBuffer buf) {

        if (buf == null)
            buf = new StringBuffer(data.length * 3 / 2);

        int end = len - 3;
        int i = start;
        int n = 0;

        while (i <= end) {
            int d =
                ((((int) data[i]) & 0x0ff) << 16)
                    | ((((int) data[i + 1]) & 0x0ff) << 8)
                    | (((int) data[i + 2]) & 0x0ff);

            buf.append(charTab[(d >> 18) & 63]);
            buf.append(charTab[(d >> 12) & 63]);
            buf.append(charTab[(d >> 6) & 63]);
            buf.append(charTab[d & 63]);

            i += 3;

            if (n++ >= 14) {
                n = 0;
                buf.append("\r\n");
            }
        }

        if (i == start + len - 2) {
            int d =
                ((((int) data[i]) & 0x0ff) << 16)
                    | ((((int) data[i + 1]) & 255) << 8);

            buf.append(charTab[(d >> 18) & 63]);
            buf.append(charTab[(d >> 12) & 63]);
            buf.append(charTab[(d >> 6) & 63]);
            buf.append("=");
        }
        else if (i == start + len - 1) {
            int d = (((int) data[i]) & 0x0ff) << 16;

            buf.append(charTab[(d >> 18) & 63]);
            buf.append(charTab[(d >> 12) & 63]);
            buf.append("==");
        }

        return buf;
    }

    static int decode(char c) {
        if (c >= 'A' && c <= 'Z')
            return ((int) c) - 65;
        else if (c >= 'a' && c <= 'z')
            return ((int) c) - 97 + 26;
        else if (c >= '0' && c <= '9')
            return ((int) c) - 48 + 26 + 26;
        else
            switch (c) {
                case '+' :
                    return 62;
                case '/' :
                    return 63;
                case '=' :
                    return 0;
                default :
                    throw new RuntimeException(
                        "unexpected code: " + c);
            }
    }

    /** Decodes the given Base64 encoded String to a new byte array. 
    The byte array holding the decoded data is returned. */

    public static byte[] decode(String s) {

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try {
            decode(s, bos);
        }
        catch (IOException e) {
            throw new RuntimeException();
        }
        return bos.toByteArray();
    }

    public static void decode(String s, OutputStream os)
        throws IOException {
        int i = 0;

        int len = s.length();

        while (true) {
            while (i < len && s.charAt(i) <= ' ')
                i++;

            if (i == len)
                break;

            int tri =
                (decode(s.charAt(i)) << 18)
                    + (decode(s.charAt(i + 1)) << 12)
                    + (decode(s.charAt(i + 2)) << 6)
                    + (decode(s.charAt(i + 3)));

            os.write((tri >> 16) & 255);
            if (s.charAt(i + 2) == '=')
                break;
            os.write((tri >> 8) & 255);
            if (s.charAt(i + 3) == '=')
                break;
            os.write(tri & 255);

            i += 4;
        }
    }
}