Mega Code Archive
Encode and decode data in Base64 format as described in RFC 1521
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/**************************************************************************
*
* A Base64 Encoder/Decoder.
*
* This class is used to encode and decode data in Base64 format
* as described in RFC 1521.
*
* <p>
* Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.<br>
* License: This is "Open Source" software and released under the <a href="http://www.gnu.org/licenses/lgpl.html" target="_top">GNU/LGPL</a> license.
* It is provided "as is" without warranty of any kind. Please contact the author for other licensing arrangements.<br>
* Home page: <a href="http://www.source-code.biz" target="_top">www.source-code.biz</a><br>
*
* <p>
* Version history:<br>
* 2003-07-22 Christian d'Heureuse (chdh): Module created.<br>
* 2005-08-11 chdh: Lincense changed from GPL to LGPL.
*
**************************************************************************/
public class 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;
}
/**
* Encodes a string into Base64 format.
* No blanks or line breaks are inserted.
* @param s a String to be encoded.
* @return A String with the Base64 encoded data.
*/
public static String encode(String s) {
return new String(encode(s.getBytes()));
}
/**
* 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 with 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;
}
/**
* Decodes a Base64 string.
* @param s a 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()));
}
/**
* Decodes Base64 data.
* 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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