Mega Code Archive
Helper class to provide Base64 encoding routines
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/*******************************************************************************
* Copyright (C) 2006 Google Inc.
*
* 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.
******************************************************************************/
/**
* Helper class to provide Base64 encoding routines.
*
* @author ? - added by ksim
* @date March 6th, 2007
* @version 1.0
* @todo Not unit tested yet.
*/
/**
* The <b>Base64Coder</b> class provides methods for encoding strings and byte
* arrays into Base64 format. It also provides methods for decoding
* Base64-encoded strings and character arrays.
*
* @version 1.0 beta
*/
public class Base64Coder {
private Base64Coder() {
}
/**
* Mapping table from 6-bit nibbles to Base64 characters.
*/
private static char[] map1 = new char[64];
static {
int i = 0;
for (char c = 'A'; c <= 'Z'; c++) {
map1[i++] = c;
}
for (char c = 'a'; c <= 'z'; c++) {
map1[i++] = c;
}
for (char c = '0'; c <= '9'; c++) {
map1[i++] = c;
}
map1[i++] = '+';
map1[i++] = '/';
}
/**
* Mapping table from Base64 characters to 6-bit nibbles.
*/
private static byte[] map2 = new byte[128];
static {
for (int i = 0; i < map2.length; i++) {
map2[i] = -1;
}
for (int i = 0; i < 64; i++) {
map2[map1[i]] = (byte) i;
}
}
/**
* The <b>encode (String s)</b> method encodes a string into Base64 format.
* No blanks or line breaks are inserted.
*
* @param s
* The string to be encoded.
* @return String in Base64-encoded format.
*/
public static String encode(String s) {
return new String(encode(s.getBytes()));
}
/**
* The <b>encode (byte[] in)</b> method encodes a byte array into Base64
* format. No blanks or line breaks are inserted.
*
* @param in
* An array containing the data bytes to be encoded.
* @return A character array containing the Base64-encoded data.
*/
public static char[] encode(byte[] in) {
int iLen = in.length;
int oDataLen = (iLen * 4 + 2) / 3; // output length without padding
int oLen = ((iLen + 2) / 3) * 4; // output length including padding
char[] out = new char[oLen];
int ip = 0;
int op = 0;
while (ip < iLen) {
int i0 = in[ip++] & 0xff;
int i1 = ip < iLen ? in[ip++] & 0xff : 0;
int i2 = ip < iLen ? in[ip++] & 0xff : 0;
int o0 = i0 >>> 2;
int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
int o3 = i2 & 0x3F;
out[op++] = map1[o0];
out[op++] = map1[o1];
out[op] = op < oDataLen ? map1[o2] : '=';
op++;
out[op] = op < oDataLen ? map1[o3] : '=';
op++;
}
return out;
}
/**
* The <b>decode (String s)</b> method decodes a Base64-encoded string.
*
* @param s
* The Base64 String to be decoded.
* @return A String containing the decoded data.
* @throws IllegalArgumentException
* if the input is not valid Base64-encoded data.
*/
public static String decode(String s) {
return new String(decode(s.toCharArray()));
}
/**
* The <b>decode (char[] in)</b> method decodes an array of Base64-encoded
* characters. No blanks or line breaks are allowed within the
* Base64-encoded data.
*
* @param in
* A character array containing the Base64-encoded data.
* @return An array containing the decoded data bytes.
* @throws IllegalArgumentException
* if the input is not valid Base64-encoded data.
*/
public static byte[] decode(char[] in) {
int iLen = in.length;
if (iLen % 4 != 0)
throw new IllegalArgumentException(
"Length of Base64 encoded input "
+ "string is not a multiple of 4.");
while (iLen > 0 && in[iLen - 1] == '=')
iLen--;
int oLen = (iLen * 3) / 4;
byte[] out = new byte[oLen];
int ip = 0;
int op = 0;
while (ip < iLen) {
int i0 = in[ip++];
int i1 = in[ip++];
int i2 = ip < iLen ? in[ip++] : 'A';
int i3 = ip < iLen ? in[ip++] : 'A';
if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
throw new IllegalArgumentException("Illegal character in "
+ "Base64 encoded data.");
int b0 = map2[i0];
int b1 = map2[i1];
int b2 = map2[i2];
int b3 = map2[i3];
if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
throw new IllegalArgumentException(
"Illegal character in Base64 " + "encoded data.");
int o0 = (b0 << 2) | (b1 >>> 4);
int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
int o2 = ((b2 & 3) << 6) | b3;
out[op++] = (byte) o0;
if (op < oLen) {
out[op++] = (byte) o1;
}
if (op < oLen) {
out[op++] = (byte) o2;
}
}
return out;
}
}
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