package org.basex.util;
import static org.basex.util.Token.*;
import org.basex.util.list.ByteList;
/**
* This class provides functions for encoding and decoding Base64 strings.
*
* @author BaseX Team 2005-12, BSD License
* @author Christian Gruen
*/
public final class Base64 {
/** Ending characters. */
private static final byte[] ENDING = token("AQgw");
/** Hidden constructor. */
private Base64() { }
/**
* Encodes the specified string.
* @param token value to be encoded
* @return resulting token
*/
public static String encode(final String token) {
return string(encode(token(token)));
}
/**
* Encodes the specified token.
* @param token value to be encoded
* @return resulting token
*/
public static byte[] encode(final byte[] token) {
final ByteList bl = new ByteList();
final int a = token.length;
final int f = a / 3;
final int p = a - 3 * f;
int c = 0;
for(int i = 0; i < f; ++i) {
final int b0 = token[c++] & 0xff;
final int b1 = token[c++] & 0xff;
final int b2 = token[c++] & 0xff;
bl.add(H2B[b0 >> 2]);
bl.add(H2B[b0 << 4 & 0x3f | b1 >> 4]);
bl.add(H2B[b1 << 2 & 0x3f | b2 >> 6]);
bl.add(H2B[b2 & 0x3f]);
}
if(p != 0) {
final int b0 = token[c++] & 0xff;
bl.add(H2B[b0 >> 2]);
if(p == 1) {
bl.add(H2B[b0 << 4 & 0x3f]);
bl.add('=');
bl.add('=');
} else {
final int b1 = token[c] & 0xff;
bl.add(H2B[b0 << 4 & 0x3f | b1 >> 4]);
bl.add(H2B[b1 << 2 & 0x3f]);
bl.add('=');
}
}
return bl.toArray();
}
/** Hex to byte conversion table. */
private static final byte[] H2B = { '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 the specified string.
* @param token value to be decoded
* @return resulting token
*/
public static String decode(final String token) {
return string(decode(token(token)));
}
/**
* Decodes the specified token.
* @param token value to be decoded
* @return resulting token
*/
public static byte[] decode(final byte[] token) {
final ByteList bl = new ByteList();
for(final byte c : token) if(c < 0 || c > ' ') bl.add(c);
final byte[] s = bl.toArray();
if((s.length & 3) != 0) error(s);
final int l = s.length;
final int g = l >>> 2;
int m = 0, n = g;
if(l != 0) {
if(s[l - 1] == '=') {
++m;
--n;
}
if(s[l - 2] == '=') ++m;
if(m == 2 && !contains(ENDING, s[l - 3])) error(substring(s, l - 3));
}
final byte[] val = new byte[3 * g - m];
int c = 0, o = 0;
for(int i = 0; i < n; ++i) {
final int c0 = b2h(s[c++]);
final int c1 = b2h(s[c++]);
final int c2 = b2h(s[c++]);
final int c3 = b2h(s[c++]);
val[o++] = (byte) (c0 << 2 | c1 >> 4);
val[o++] = (byte) (c1 << 4 | c2 >> 2);
val[o++] = (byte) (c2 << 6 | c3);
}
if(m != 0) {
final int c0 = b2h(s[c++]);
final int c1 = b2h(s[c++]);
val[o++] = (byte) (c0 << 2 | c1 >> 4);
if(m == 1) val[o] = (byte) (c1 << 4 | b2h(s[c]) >> 2);
}
return val;
}
/** Byte to hex conversion table. */
private static final byte[] B2H = { -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
};
/**
* Converts a single byte to its hex representation.
* @param c character to be encoded
* @return encoded value
*/
private static int b2h(final byte c) {
if(c < 0 || c >= B2H.length) error((char) c);
final int result = B2H[c];
if(result < 0) error((char) c);
return result;
}
/**
* Throws an illegal argument exception for the specified character.
* @param a character
*/
private static void error(final Object a) {
throw new IllegalArgumentException(Util.info("Invalid Base64 cast: %.", a));
}
}