Data Encoding Tutorials - Herong's Tutorial Examples - v5.23, by Herong Yang
Bitpedia Implementation of Base32 in Java
This section provides a Java implementation of the Base32 encoding algorithm by the Bitcollider project.
One of the Java implementations of Base32 encoding algorithm available on the Internet is from Bitcollider project under the Bitpedia organization at https://sourceforge.net/projects/bitcollider/.
/* (PD) 2006 The Bitzi Corporation
* Please see http://bitzi.com/publicdomain for more info.
*
* $Id: Base32.java,v 1.2 2006/07/14 04:58:39 gojomo Exp $
*/
package org.bitpedia.util;
/**
* Base32 - encodes and decodes RFC3548 Base32
* (see http://www.faqs.org/rfcs/rfc3548.html )
*
* @author Robert Kaye
* @author Gordon Mohr
*/
public class Base32 {
private static final String base32Chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
private static final int[] base32Lookup =
{ 0xFF,0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06,
0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,
0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16,
0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06,
0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,
0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16,
0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF
};
/**
* Encodes byte array to Base32 String.
*
* @param bytes Bytes to encode.
* @return Encoded byte array <code>bytes</code> as a String.
*
*/
static public String encode(final byte[] bytes) {
int i = 0, index = 0, digit = 0;
int currByte, nextByte;
StringBuffer base32
= new StringBuffer((bytes.length + 7) * 8 / 5);
while (i < bytes.length) {
currByte = (bytes[i] >= 0) ? bytes[i] : (bytes[i] + 256);
/* Is the current digit going to span a byte boundary? */
if (index > 3) {
if ((i + 1) < bytes.length) {
nextByte = (bytes[i + 1] >= 0)
? bytes[i + 1] : (bytes[i + 1] + 256);
} else {
nextByte = 0;
}
digit = currByte & (0xFF >> index);
index = (index + 5) % 8;
digit <<= index;
digit |= nextByte >> (8 - index);
i++;
} else {
digit = (currByte >> (8 - (index + 5))) & 0x1F;
index = (index + 5) % 8;
if (index == 0)
i++;
}
base32.append(base32Chars.charAt(digit));
}
return base32.toString();
}
/**
* Decodes the given Base32 String to a raw byte array.
*
* @param base32
* @return Decoded <code>base32</code> String as a raw byte array.
*/
static public byte[] decode(final String base32) {
int i, index, lookup, offset, digit;
byte[] bytes = new byte[base32.length() * 5 / 8];
for (i = 0, index = 0, offset = 0; i < base32.length(); i++) {
lookup = base32.charAt(i) - '0';
/* Skip chars outside the lookup table */
if (lookup < 0 || lookup >= base32Lookup.length) {
continue;
}
digit = base32Lookup[lookup];
/* If this digit is not in the table, ignore it */
if (digit == 0xFF) {
continue;
}
if (index <= 3) {
index = (index + 5) % 8;
if (index == 0) {
bytes[offset] |= digit;
offset++;
if (offset >= bytes.length)
break;
} else {
bytes[offset] |= digit << (8 - index);
}
} else {
index = (index + 5) % 8;
bytes[offset] |= (digit >>> index);
offset++;
if (offset >= bytes.length) {
break;
}
bytes[offset] |= digit << (8 - index);
}
}
return bytes;
}
/** For testing, take a command-line argument in Base32, decode,
* print in hex, encode, print
*
* @param args
*/
static public void main(String[] args) {
if (args.length == 0) {
System.out.println("Supply a Base32-encoded argument.");
return;
}
System.out.println(" Original: " + args[0]);
byte[] decoded = Base32.decode(args[0]);
System.out.print(" Hex: ");
for (int i = 0; i < decoded.length; i++) {
int b = decoded[i];
if (b < 0) {
b += 256;
}
System.out.print(
(Integer.toHexString(b + 256)).substring(1));
}
System.out.println();
System.out.println("Reencoded: " + Base32.encode(decoded));
}
}
See the next section for a testing program and test results.
Table of Contents
Base64 Encoding and Decoding Tools
Base64URL - URL Safe Base64 Encoding
►Bitpedia Implementation of Base32 in Java
Bitpedia Implementation of Base32 in Java - Test
Andre's Implementation of Base32 in PHP
Andre's Implementation of Base32 in PHP - Test
madebits Implementation of Base32 in C++