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A versatile Java(TM) library that implements many useful container and utility classes.
/*
* de.unkrig.commons - A general-purpose Java class library
*
* Copyright (c) 2012, Arno Unkrig
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
* following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package de.unkrig.commons.util;
import de.unkrig.commons.lang.AssertionUtil;
/**
* A BASE64 encoder and a decoder.
*
* @see Wikipedia
*/
public final
class Base64 {
static { AssertionUtil.enableAssertionsForThisClass(); }
private Base64() {}
/**
* Encodes a series of bytes into a BASE64 string.
*/
public static String
byteArrayToBase64(byte[] a) {
int aLen = a.length;
int numFullGroups = aLen / 3;
int numBytesInPartialGroup = aLen - 3 * numFullGroups;
int resultLen = 4 * ((aLen + 2) / 3);
StringBuffer result = new StringBuffer(resultLen);
char[] intToAlpha = Base64.INT_TO_BASE64;
int inCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
final int byte0 = a[inCursor++] & 0xff;
final int byte1 = a[inCursor++] & 0xff;
final int byte2 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
result.append(intToAlpha[byte2 & 0x3f]);
}
if (numBytesInPartialGroup != 0) {
int byte0 = a[inCursor++] & 0xff;
result.append(intToAlpha[byte0 >> 2]);
if (numBytesInPartialGroup == 1) {
result.append(intToAlpha[(byte0 << 4) & 0x3f]);
result.append("==");
} else {
// assert numBytesInPartialGroup == 2;
int byte1 = a[inCursor++] & 0xff;
result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
result.append(intToAlpha[(byte1 << 2) & 0x3f]);
result.append('=');
}
}
return result.toString();
}
/**
* This array is a lookup table that translates 6-bit positive integer index
* values into their "Base64 Alphabet" equivalents as specified in Table 1
* of RFC 2045.
*/
private static final char[] INT_TO_BASE64 = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3',
'4', '5', '6', '7', '8', '9', '+', '/',
};
/**
* Decodes a BASE64 string into a series of bytes.
*/
public static byte[]
base64ToByteArray(String s) {
final byte[] alphaToInt = Base64.BASE64_TO_INT;
final int sLen = s.length();
final int numGroups = sLen / 4;
if (4 * numGroups != sLen) throw new IllegalArgumentException("String length must be a multiple of four.");
int missingBytesInLastGroup = 0;
int numFullGroups = numGroups;
if (sLen != 0) {
if (s.charAt(sLen - 1) == '=') {
missingBytesInLastGroup++;
numFullGroups--;
}
if (s.charAt(sLen - 2) == '=') missingBytesInLastGroup++;
}
byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];
int inCursor = 0, outCursor = 0;
for (int i = 0; i < numFullGroups; i++) {
final int ch0 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
final int ch1 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
final int ch2 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
final int ch3 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
result[outCursor++] = (byte) ((ch2 << 6) | ch3);
}
if (missingBytesInLastGroup != 0) {
int ch0 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
int ch1 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
if (missingBytesInLastGroup == 1) {
int ch2 = Base64.base64toInt(s.charAt(inCursor++), alphaToInt);
result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
}
}
return result;
}
/**
* Translates the specified character, which is assumed to be in the
* "Base 64 Alphabet" into its equivalent 6-bit positive integer.
*
* @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not
* in the Base64 Alphabet.
*/
private static int
base64toInt(char c, byte[] alphaToInt) {
int result = alphaToInt[c];
if (result < 0) throw new IllegalArgumentException("Illegal character " + c);
return result;
}
/**
* This array is a lookup table that translates unicode characters drawn
* from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045) into
* their 6-bit positive integer equivalents. Characters that are not in the
* Base64 alphabet but fall within the bounds of the array are translated to
* -1.
*/
private static final byte[] BASE64_TO_INT = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1,
-1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
};
}