//////////////////////license & copyright header/////////////////////////
// //
// Base64 - encode/decode data using the Base64 encoding scheme //
// //
// Copyright (c) 1998 by Kevin Kelley //
// //
// 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, or contact the author: //
// //
// Kevin Kelley <kelley@ruralnet.net> - 30718 Rd. 28, La Junta, CO, //
// 81050 USA. //
// //
////////////////////end license & copyright header///////////////////////
package soot.tagkit;
/**
* Provides encoding of raw bytes to base64-encoded characters, and
* decoding of base64 characters to raw bytes.
*
* @author Kevin Kelley (kelley@ruralnet.net)
* @version 1.3
* @date 06 August 1998
* @modified 14 February 2000
* @modified 22 September 2000
*/
public class Base64 {
/**
* returns an array of base64-encoded characters to represent the
* passed data array.
*
* @param data the array of bytes to encode
* @return base64-coded character array.
*/
static public char[] encode(byte[] data)
{
char[] out = new char[((data.length + 2) / 3) * 4];
//
// 3 bytes encode to 4 chars. Output is always an even
// multiple of 4 characters.
//
for (int i=0, index=0; i<data.length; i+=3, index+=4) {
boolean quad = false;
boolean trip = false;
int val = (0xFF & data[i]);
val <<= 8;
if ((i+1) < data.length) {
val |= (0xFF & data[i+1]);
trip = true;
}
val <<= 8;
if ((i+2) < data.length) {
val |= (0xFF & data[i+2]);
quad = true;
}
out[index+3] = alphabet[(quad? (val & 0x3F): 64)];
val >>= 6;
out[index+2] = alphabet[(trip? (val & 0x3F): 64)];
val >>= 6;
out[index+1] = alphabet[val & 0x3F];
val >>= 6;
out[index+0] = alphabet[val & 0x3F];
}
return out;
}
/**
* Decodes a BASE-64 encoded stream to recover the original
* data. White space before and after will be trimmed away,
* but no other manipulation of the input will be performed.
*
* As of version 1.2 this method will properly handle input
* containing junk characters (newlines and the like) rather
* than throwing an error. It does this by pre-parsing the
* input and generating from that a count of VALID input
* characters.
**/
static public byte[] decode(char[] data)
{
// as our input could contain non-BASE64 data (newlines,
// whitespace of any sort, whatever) we must first adjust
// our count of USABLE data so that...
// (a) we don't misallocate the output array, and
// (b) think that we miscalculated our data length
// just because of extraneous throw-away junk
int tempLen = data.length;
for (char element : data) {
if( (element > 255) || codes[ element ] < 0 )
--tempLen; // ignore non-valid chars and padding
}
// calculate required length:
// -- 3 bytes for every 4 valid base64 chars
// -- plus 2 bytes if there are 3 extra base64 chars,
// or plus 1 byte if there are 2 extra.
int len = (tempLen / 4) * 3;
if ((tempLen % 4) == 3) len += 2;
if ((tempLen % 4) == 2) len += 1;
byte[] out = new byte[len];
int shift = 0; // # of excess bits stored in accum
int accum = 0; // excess bits
int index = 0;
for (char element : data) {
int value = (element>255)? -1: codes[ element ];
if ( value >= 0 ) // skip over non-code
{
accum <<= 6; // bits shift up by 6 each time thru
shift += 6; // loop, with new bits being put in
accum |= value; // at the bottom.
if ( shift >= 8 ) // whenever there are 8 or more shifted in,
{
shift -= 8; // write them out (from the top, leaving any
out[index++] = // excess at the bottom for next iteration.
(byte) ((accum >> shift) & 0xff);
}
}
// we will also have skipped processing a padding null byte ('=') here;
// these are used ONLY for padding to an even length and do not legally
// occur as encoded data. for this reason we can ignore the fact that
// no index++ operation occurs in that special case: the out[] array is
// initialized to all-zero bytes to start with and that works to our
// advantage in this combination.
}
// if there is STILL something wrong we just have to throw up now!
if( index != out.length)
{
throw new Error("Miscalculated data length (wrote " + index + " instead of " + out.length + ")");
}
return out;
}
//
// code characters for values 0..63
//
private static final char[] alphabet =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
.toCharArray();
//
// lookup table for converting base64 characters to value in range 0..63
//
private static final byte[] codes = new byte[256];
static {
for (int i=0; i<256; i++) codes[i] = -1;
for (int i = 'A'; i <= 'Z'; i++) codes[i] = (byte)( i - 'A');
for (int i = 'a'; i <= 'z'; i++) codes[i] = (byte)(26 + i - 'a');
for (int i = '0'; i <= '9'; i++) codes[i] = (byte)(52 + i - '0');
codes['+'] = 62;
codes['/'] = 63;
}
}