Listing 3: Base64Utils.java
/**
* Provides utilities for Base64 encode/decode of binary data.
*/
public class Base64Utils {
private static byte[] mBase64EncMap, mBase64DecMap;
/**
* Class initializer. Initializes the Base64 alphabet
* (specified in RFC-2045).
*/
static {
byte[] base64Map = {
(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)'/' };
mBase64EncMap = base64Map;
mBase64DecMap = new byte[128];
for (int i=0; i<mBase64EncMap.length; i++)
mBase64DecMap[mBase64EncMap[i]] = (byte) i;
}
/**
* This class isn't meant to be instantiated.
*/
private Base64Utils() {
}
/**
* Encodes the given byte[] using the Base64-encoding,
* as specified in RFC-2045 (Section 6.8).
*
* @param aData the data to be encoded
* @return the Base64-encoded <var>aData</var>
* @exception IllegalArgumentException if NULL or empty
* array is passed
*/
public static String base64Encode(byte[] aData) {
if ((aData == null) || (aData.length == 0))
throw new IllegalArgumentException(
"Cannot encode NULL or empty byte array.");
byte encodedBuf[] = new byte[((aData.length+2)/3)*4];
// 3-byte to 4-byte conversion
int srcIndex, destIndex;
for (srcIndex=0, destIndex=0; srcIndex < aData.length-2;
srcIndex += 3) {
encodedBuf[destIndex++] =
mBase64EncMap[(aData[srcIndex] >>> 2) & 077];
encodedBuf[destIndex++] = mBase64EncMap[
(aData[srcIndex+1] >>> 4) & 017 |
(aData[srcIndex] << 4) & 077];
encodedBuf[destIndex++] = mBase64EncMap[
(aData[srcIndex+2] >>> 6) & 003 |
(aData[srcIndex+1] << 2) & 077];
encodedBuf[destIndex++] = mBase64EncMap[
aData[srcIndex+2] & 077];
}
// Convert the last 1 or 2 bytes
if (srcIndex < aData.length) {
encodedBuf[destIndex++] =
mBase64EncMap[(aData[srcIndex] >>> 2) & 077];
if (srcIndex < aData.length-1) {
encodedBuf[destIndex++] =
mBase64EncMap[(aData[srcIndex+1] >>> 4) & 017 |
(aData[srcIndex] << 4) & 077];
encodedBuf[destIndex++] =
mBase64EncMap[(aData[srcIndex+1] << 2) & 077];
}
else {
encodedBuf[destIndex++] =
mBase64EncMap[(aData[srcIndex] << 4) & 077];
}
}
// Add padding to the end of encoded data
while (destIndex < encodedBuf.length) {
encodedBuf[destIndex] = (byte) '=';
destIndex++;
}
String result = new String(encodedBuf);
return result;
}
/**
* Decodes the given Base64-encoded data,
* as specified in RFC-2045 (Section 6.8).
*
* @param aData the Base64-encoded aData.
* @return the decoded <var>aData</var>.
* @exception IllegalArgumentException if NULL or empty data
* is passed
*/
public static byte[] base64Decode(String aData) {
if ((aData == null) || (aData.length() == 0))
throw new IllegalArgumentException(
"Cannot decode NULL or empty string.");
byte[] data = aData.getBytes();
// Skip padding from the end of encoded data
int tail = data.length;
while (data[tail-1] == '=')
tail--;
byte decodedBuf[] = new byte[tail - data.length/4];
// ASCII-printable to 0-63 conversion
for (int i = 0; i < data.length; i++)
data[i] = mBase64DecMap[data[i]];
// 4-byte to 3-byte conversion
int srcIndex, destIndex;
for (srcIndex = 0, destIndex=0; destIndex < decodedBuf.length-2;
srcIndex += 4, destIndex += 3) {
decodedBuf[destIndex] = (byte)
( ((data[srcIndex] << 2) & 255) |
((data[srcIndex+1] >>> 4) & 003) );
decodedBuf[destIndex+1] = (byte)
( ((data[srcIndex+1] << 4) & 255) |
((data[srcIndex+2] >>> 2) & 017) );
decodedBuf[destIndex+2] = (byte)
( ((data[srcIndex+2] << 6) & 255) |
(data[srcIndex+3] & 077) );
}
// Handle last 1 or 2 bytes
if (destIndex < decodedBuf.length)
decodedBuf[destIndex] = (byte) (
((data[srcIndex] << 2) & 255) |
((data[srcIndex+1] >>> 4) & 003) );
if (++destIndex < decodedBuf.length)
decodedBuf[destIndex] = (byte)
( ((data[srcIndex+1] << 4) & 255) |
((data[srcIndex+2] >>> 2) & 017) );
return decodedBuf;
}
}
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