Implementation of MIME's Base64 encoding and decoding conversions.
/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
public class Base64 {
/**
* Implementation of MIME's Base64 encoding and decoding conversions.
* Optimized code. (raw version taken from oreilly.jonathan.util, and
* currently org.apache.xerces.ds.util.Base64)
*
* @author Raul Benito(Of the xerces copy, and little adaptations).
* @author Anli Shundi
* @author Christian Geuer-Pollmann
* @see <A HREF="ftp://ftp.isi.edu/in-notes/rfc2045.txt">RFC 2045</A>
* @see org.apache.xml.security.transforms.implementations.TransformBase64Decode
*/
/**
* Field BASE64DEFAULTLENGTH
*/
public static final int BASE64DEFAULTLENGTH = 76;
/**
* Field _base64length
*/
static int _base64length = Base64.BASE64DEFAULTLENGTH;
static private final int BASELENGTH = 255;
static private final int LOOKUPLENGTH = 64;
static private final int TWENTYFOURBITGROUP = 24;
static private final int EIGHTBIT = 8;
static private final int SIXTEENBIT = 16;
static private final int FOURBYTE = 4;
static private final int SIGN = -128;
static private final char PAD = '=';
static final private byte[] base64Alphabet = new byte[BASELENGTH];
static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];
static {
for (int i = 0; i < BASELENGTH; i++) {
base64Alphabet[i] = -1;
}
for (int i = 'Z'; i >= 'A'; i--) {
base64Alphabet[i] = (byte) (i - 'A');
}
for (int i = 'z'; i >= 'a'; i--) {
base64Alphabet[i] = (byte) (i - 'a' + 26);
}
for (int i = '9'; i >= '0'; i--) {
base64Alphabet[i] = (byte) (i - '0' + 52);
}
base64Alphabet['+'] = 62;
base64Alphabet['/'] = 63;
for (int i = 0; i <= 25; i++)
lookUpBase64Alphabet[i] = (char) ('A' + i);
for (int i = 26, j = 0; i <= 51; i++, j++)
lookUpBase64Alphabet[i] = (char) ('a' + j);
for (int i = 52, j = 0; i <= 61; i++, j++)
lookUpBase64Alphabet[i] = (char) ('0' + j);
lookUpBase64Alphabet[62] = '+';
lookUpBase64Alphabet[63] = '/';
}
private Base64() {
// we don't allow instantiation
}
/**
* Encode a byte array and fold lines at the standard 76th character.
*
* @param binaryData
* <code>byte[]<code> to be base64 encoded
* @return the <code>String<code> with encoded data
*/
public static String encode(byte[] binaryData) {
return encode(binaryData, BASE64DEFAULTLENGTH, false);
}
protected static boolean isWhiteSpace(byte octect) {
return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
}
protected static boolean isPad(byte octect) {
return (octect == PAD);
}
/**
* Encode a byte array in Base64 format and return an optionally wrapped line.
*
* @param binaryData
* <code>byte[]</code> data to be encoded
* @param length
* <code>int<code> length of wrapped lines; No wrapping if less than 4.
* @return a <code>String</code> with encoded data
*/
public static String encode(byte[] binaryData, int length, boolean wrap) {
if (length < 4) {
length = Integer.MAX_VALUE;
}
if (binaryData == null)
return null;
int lengthDataBits = binaryData.length * EIGHTBIT;
if (lengthDataBits == 0) {
return "";
}
int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
int quartesPerLine = length / 4;
int numberLines = (numberQuartet - 1) / quartesPerLine;
char encodedData[];
encodedData = new char[(numberQuartet * 4) + (wrap ? numberLines : 0)];
byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
int encodedIndex = 0;
int dataIndex = 0;
int tripletsDone = 0;
for (int line = 0; line < numberLines; line++) {
for (int quartet = 0; quartet < quartesPerLine; quartet++) {
b1 = binaryData[dataIndex++];
b2 = binaryData[dataIndex++];
b3 = binaryData[dataIndex++];
l = (byte) (b2 & 0x0f);
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
tripletsDone++;
}
if (wrap) {
encodedData[encodedIndex++] = 0xa;
}
}
for (; tripletsDone < numberTriplets; tripletsDone++) {
b1 = binaryData[dataIndex++];
b2 = binaryData[dataIndex++];
b3 = binaryData[dataIndex++];
l = (byte) (b2 & 0x0f);
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
}
// form integral number of 6-bit groups
if (fewerThan24bits == EIGHTBIT) {
b1 = binaryData[dataIndex];
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
encodedData[encodedIndex++] = PAD;
encodedData[encodedIndex++] = PAD;
} else if (fewerThan24bits == SIXTEENBIT) {
b1 = binaryData[dataIndex];
b2 = binaryData[dataIndex + 1];
l = (byte) (b2 & 0x0f);
k = (byte) (b1 & 0x03);
byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
encodedData[encodedIndex++] = PAD;
}
return new String(encodedData);
}
/**
* Decodes Base64 data into octects
*
* @param encoded
* String containing Base64 data
* @return Array containing decoded data.
*/
public static byte[] decode(String encoded) throws RuntimeException {
byte[] base64Data = encoded.getBytes();
// remove white spaces
int len = removeWhiteSpace(base64Data);
if (len % FOURBYTE != 0) {
throw new RuntimeException("decoding.divisible.four");
// should be divisible by four
}
int numberQuadruple = (len / FOURBYTE);
if (numberQuadruple == 0)
return new byte[0];
byte decodedData[] = null;
byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
int i = 0;
int encodedIndex = 0;
int dataIndex = 0;
// decodedData = new byte[ (numberQuadruple)*3];
dataIndex = (numberQuadruple - 1) * 4;
encodedIndex = (numberQuadruple - 1) * 3;
// first last bits.
b1 = base64Alphabet[base64Data[dataIndex++]];
b2 = base64Alphabet[base64Data[dataIndex++]];
if ((b1 == -1) || (b2 == -1)) {
throw new RuntimeException("decoding.general");// if found "no data" just
// return null
}
byte d3, d4;
b3 = base64Alphabet[d3 = base64Data[dataIndex++]];
b4 = base64Alphabet[d4 = base64Data[dataIndex++]];
if ((b3 == -1) || (b4 == -1)) {
// Check if they are PAD characters
if (isPad(d3) && isPad(d4)) { // Two PAD e.g. 3c[Pad][Pad]
if ((b2 & 0xf) != 0)// last 4 bits should be zero
throw new RuntimeException("decoding.general");
decodedData = new byte[encodedIndex + 1];
decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
} else if (!isPad(d3) && isPad(d4)) { // One PAD e.g. 3cQ[Pad]
if ((b3 & 0x3) != 0)// last 2 bits should be zero
throw new RuntimeException("decoding.general");
decodedData = new byte[encodedIndex + 2];
decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
} else {
throw new RuntimeException("decoding.general");// an error like
// "3c[Pad]r", "3cdX",
// "3cXd", "3cXX" where
// X is non data
}
} else {
// No PAD e.g 3cQl
decodedData = new byte[encodedIndex + 3];
decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
}
encodedIndex = 0;
dataIndex = 0;
// the begin
for (i = numberQuadruple - 1; i > 0; i--) {
b1 = base64Alphabet[base64Data[dataIndex++]];
b2 = base64Alphabet[base64Data[dataIndex++]];
b3 = base64Alphabet[base64Data[dataIndex++]];
b4 = base64Alphabet[base64Data[dataIndex++]];
if ((b1 == -1) || (b2 == -1) || (b3 == -1) || (b4 == -1)) {
throw new RuntimeException("decoding.general");// if found "no data"
// just return null
}
decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
}
return decodedData;
}
/**
* remove WhiteSpace from MIME containing encoded Base64 data.
*
* @param data
* the byte array of base64 data (with WS)
* @return the new length
*/
protected static int removeWhiteSpace(byte[] data) {
if (data == null)
return 0;
// count characters that's not whitespace
int newSize = 0;
int len = data.length;
for (int i = 0; i < len; i++) {
byte dataS = data[i];
if (!isWhiteSpace(dataS))
data[newSize++] = dataS;
}
return newSize;
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
}
}