Mega Code Archive
Base64 from Eric Glass jcifs at samba dot org
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/* Encodes and decodes to and from Base64 notation.
* Copyright (C) 2003 "Eric Glass" <jcifs at samba dot org>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
public class Base64 {
private static final String ALPHABET =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/**
* Base-64 encodes the supplied block of data. Line wrapping is not
* applied on output.
*
* @param bytes The block of data that is to be Base-64 encoded.
* @return A <code>String</code> containing the encoded data.
*/
public static String encode(byte[] bytes) {
int length = bytes.length;
if (length == 0) return "";
StringBuffer buffer =
new StringBuffer((int) Math.ceil((double) length / 3d) * 4);
int remainder = length % 3;
length -= remainder;
int block;
int i = 0;
while (i < length) {
block = ((bytes[i++] & 0xff) << 16) | ((bytes[i++] & 0xff) << 8) |
(bytes[i++] & 0xff);
buffer.append(ALPHABET.charAt(block >>> 18));
buffer.append(ALPHABET.charAt((block >>> 12) & 0x3f));
buffer.append(ALPHABET.charAt((block >>> 6) & 0x3f));
buffer.append(ALPHABET.charAt(block & 0x3f));
}
if (remainder == 0) return buffer.toString();
if (remainder == 1) {
block = (bytes[i] & 0xff) << 4;
buffer.append(ALPHABET.charAt(block >>> 6));
buffer.append(ALPHABET.charAt(block & 0x3f));
buffer.append("==");
return buffer.toString();
}
block = (((bytes[i++] & 0xff) << 8) | ((bytes[i]) & 0xff)) << 2;
buffer.append(ALPHABET.charAt(block >>> 12));
buffer.append(ALPHABET.charAt((block >>> 6) & 0x3f));
buffer.append(ALPHABET.charAt(block & 0x3f));
buffer.append("=");
return buffer.toString();
}
/**
* Decodes the supplied Base-64 encoded string.
*
* @param string The Base-64 encoded string that is to be decoded.
* @return A <code>byte[]</code> containing the decoded data block.
*/
public static byte[] decode(String string) {
int length = string.length();
if (length == 0) return new byte[0];
int pad = (string.charAt(length - 2) == '=') ? 2 :
(string.charAt(length - 1) == '=') ? 1 : 0;
int size = length * 3 / 4 - pad;
byte[] buffer = new byte[size];
int block;
int i = 0;
int index = 0;
while (i < length) {
block = (ALPHABET.indexOf(string.charAt(i++)) & 0xff) << 18 |
(ALPHABET.indexOf(string.charAt(i++)) & 0xff) << 12 |
(ALPHABET.indexOf(string.charAt(i++)) & 0xff) << 6 |
(ALPHABET.indexOf(string.charAt(i++)) & 0xff);
buffer[index++] = (byte) (block >>> 16);
if (index < size) buffer[index++] = (byte) ((block >>> 8) & 0xff);
if (index < size) buffer[index++] = (byte) (block & 0xff);
}
return buffer;
}
}
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