package net.oschina.gitapp.util;
import static net.oschina.gitapp.common.Contanst.CHARSET_UTF8;
import java.io.UnsupportedEncodingException;
import java.text.MessageFormat;
import java.util.Arrays;
/**
* Encodes and decodes to and from Base64 notation.
* <p>
* I am placing this code in the Public Domain. Do with it as you will. This
* software comes with no guarantees or warranties but with plenty of
* well-wishing instead! Please visit <a
* href="http://iharder.net/base64">http://iharder.net/base64</a> periodically
* to check for updates or to contribute improvements.
* </p>
*
* @author Robert Harder
* @author rob@iharder.net
* @version 2.1, stripped to minimum feature set used by JGit.
*/
class Base64Util {
/** The equals sign (=) as a byte. */
private final static byte EQUALS_SIGN = (byte) '=';
/** Indicates equals sign in encoding. */
private final static byte EQUALS_SIGN_DEC = -1;
/** Indicates white space in encoding. */
private final static byte WHITE_SPACE_DEC = -2;
/** Indicates an invalid byte during decoding. */
private final static byte INVALID_DEC = -3;
/** The 64 valid Base64 values. */
private final static byte[] ENC;
/**
* Translates a Base64 value to either its 6-bit reconstruction value or a
* negative number indicating some other meaning. The table is only 7 bits
* wide, as the 8th bit is discarded during decoding.
*/
private final static byte[] DEC;
static {
try {
ENC = ("ABCDEFGHIJKLMNOPQRSTUVWXYZ" //
+ "abcdefghijklmnopqrstuvwxyz" //
+ "0123456789" //
+ "+/" //
).getBytes(CHARSET_UTF8);
} catch (UnsupportedEncodingException uee) {
throw new RuntimeException(uee.getMessage(), uee);
}
DEC = new byte[128];
Arrays.fill(DEC, INVALID_DEC);
for (int i = 0; i < 64; i++)
DEC[ENC[i]] = (byte) i;
DEC[EQUALS_SIGN] = EQUALS_SIGN_DEC;
DEC['\t'] = WHITE_SPACE_DEC;
DEC['\n'] = WHITE_SPACE_DEC;
DEC['\r'] = WHITE_SPACE_DEC;
DEC[' '] = WHITE_SPACE_DEC;
}
/** Defeats instantiation. */
private Base64Util() {
// Suppress empty block warning.
}
/**
* Encodes up to three bytes of the array <var>source</var> and writes the
* resulting four Base64 bytes to <var>destination</var>. The source and
* destination arrays can be manipulated anywhere along their length by
* specifying <var>srcOffset</var> and <var>destOffset</var>. This method
* does not check to make sure your arrays are large enough to accommodate
* <var>srcOffset</var> + 3 for the <var>source</var> array or
* <var>destOffset</var> + 4 for the <var>destination</var> array. The
* actual number of significant bytes in your array is given by
* <var>numSigBytes</var>.
*
* @param source
* the array to convert
* @param srcOffset
* the index where conversion begins
* @param numSigBytes
* the number of significant bytes in your array
* @param destination
* the array to hold the conversion
* @param destOffset
* the index where output will be put
*/
private static void encode3to4(byte[] source, int srcOffset,
int numSigBytes, byte[] destination, int destOffset) {
// We have to shift left 24 in order to flush out the 1's that appear
// when Java treats a value as negative that is cast from a byte.
int inBuff = 0;
switch (numSigBytes) {
case 3:
inBuff |= (source[srcOffset + 2] << 24) >>> 24;
//$FALL-THROUGH$
case 2:
inBuff |= (source[srcOffset + 1] << 24) >>> 16;
//$FALL-THROUGH$
case 1:
inBuff |= (source[srcOffset] << 24) >>> 8;
}
switch (numSigBytes) {
case 3:
destination[destOffset] = ENC[(inBuff >>> 18)];
destination[destOffset + 1] = ENC[(inBuff >>> 12) & 0x3f];
destination[destOffset + 2] = ENC[(inBuff >>> 6) & 0x3f];
destination[destOffset + 3] = ENC[(inBuff) & 0x3f];
break;
case 2:
destination[destOffset] = ENC[(inBuff >>> 18)];
destination[destOffset + 1] = ENC[(inBuff >>> 12) & 0x3f];
destination[destOffset + 2] = ENC[(inBuff >>> 6) & 0x3f];
destination[destOffset + 3] = EQUALS_SIGN;
break;
case 1:
destination[destOffset] = ENC[(inBuff >>> 18)];
destination[destOffset + 1] = ENC[(inBuff >>> 12) & 0x3f];
destination[destOffset + 2] = EQUALS_SIGN;
destination[destOffset + 3] = EQUALS_SIGN;
break;
}
}
/**
* Encodes a byte array into Base64 notation.
*
* @param source
* The data to convert
* @return encoded base64 representation of source.
*/
public static String encodeBytes(byte[] source) {
return encodeBytes(source, 0, source.length);
}
/**
* Encodes a byte array into Base64 notation.
*
* @param source
* The data to convert
* @param off
* Offset in array where conversion should begin
* @param len
* Length of data to convert
* @return encoded base64 representation of source.
*/
public static String encodeBytes(byte[] source, int off, int len) {
final int len43 = len * 4 / 3;
byte[] outBuff = new byte[len43 + ((len % 3) > 0 ? 4 : 0)];
int d = 0;
int e = 0;
int len2 = len - 2;
for (; d < len2; d += 3, e += 4)
encode3to4(source, d + off, 3, outBuff, e);
if (d < len) {
encode3to4(source, d + off, len - d, outBuff, e);
e += 4;
}
try {
return new String(outBuff, 0, e, CHARSET_UTF8);
} catch (UnsupportedEncodingException uue) {
return new String(outBuff, 0, e);
}
}
/**
* Decodes four bytes from array <var>source</var> and writes the resulting
* bytes (up to three of them) to <var>destination</var>. The source and
* destination arrays can be manipulated anywhere along their length by
* specifying <var>srcOffset</var> and <var>destOffset</var>. This method
* does not check to make sure your arrays are large enough to accommodate
* <var>srcOffset</var> + 4 for the <var>source</var> array or
* <var>destOffset</var> + 3 for the <var>destination</var> array. This
* method returns the actual number of bytes that were converted from the
* Base64 encoding.
*
* @param source
* the array to convert
* @param srcOffset
* the index where conversion begins
* @param destination
* the array to hold the conversion
* @param destOffset
* the index where output will be put
* @return the number of decoded bytes converted
*/
private static int decode4to3(byte[] source, int srcOffset,
byte[] destination, int destOffset) {
// Example: Dk==
if (source[srcOffset + 2] == EQUALS_SIGN) {
int outBuff = ((DEC[source[srcOffset]] & 0xFF) << 18)
| ((DEC[source[srcOffset + 1]] & 0xFF) << 12);
destination[destOffset] = (byte) (outBuff >>> 16);
return 1;
}
// Example: DkL=
else if (source[srcOffset + 3] == EQUALS_SIGN) {
int outBuff = ((DEC[source[srcOffset]] & 0xFF) << 18)
| ((DEC[source[srcOffset + 1]] & 0xFF) << 12)
| ((DEC[source[srcOffset + 2]] & 0xFF) << 6);
destination[destOffset] = (byte) (outBuff >>> 16);
destination[destOffset + 1] = (byte) (outBuff >>> 8);
return 2;
}
// Example: DkLE
else {
int outBuff = ((DEC[source[srcOffset]] & 0xFF) << 18)
| ((DEC[source[srcOffset + 1]] & 0xFF) << 12)
| ((DEC[source[srcOffset + 2]] & 0xFF) << 6)
| ((DEC[source[srcOffset + 3]] & 0xFF));
destination[destOffset] = (byte) (outBuff >> 16);
destination[destOffset + 1] = (byte) (outBuff >> 8);
destination[destOffset + 2] = (byte) (outBuff);
return 3;
}
}
/**
* Low-level decoding ASCII characters from a byte array.
*
* @param source
* The Base64 encoded data
* @param off
* The offset of where to begin decoding
* @param len
* The length of characters to decode
* @return decoded data
* @throws IllegalArgumentException
* the input is not a valid Base64 sequence.
*/
public static byte[] decode(byte[] source, int off, int len) {
byte[] outBuff = new byte[len * 3 / 4]; // Upper limit on size of output
int outBuffPosn = 0;
byte[] b4 = new byte[4];
int b4Posn = 0;
for (int i = off; i < off + len; i++) {
byte sbiCrop = (byte) (source[i] & 0x7f);
byte sbiDecode = DEC[sbiCrop];
if (EQUALS_SIGN_DEC <= sbiDecode) {
b4[b4Posn++] = sbiCrop;
if (b4Posn > 3) {
outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn);
b4Posn = 0;
// If that was the equals sign, break out of 'for' loop
if (sbiCrop == EQUALS_SIGN)
break;
}
} else if (sbiDecode != WHITE_SPACE_DEC)
throw new IllegalArgumentException(MessageFormat.format(
"Bad Base64 input character at {0} : {1} (decimal)", i,
source[i] & 0xff));
}
if (outBuff.length == outBuffPosn)
return outBuff;
byte[] out = new byte[outBuffPosn];
System.arraycopy(outBuff, 0, out, 0, outBuffPosn);
return out;
}
/**
* Decodes data from Base64 notation.
*
* @param s
* the string to decode
* @return the decoded data
*/
public static byte[] decode(String s) {
byte[] bytes;
try {
bytes = s.getBytes(CHARSET_UTF8);
} catch (UnsupportedEncodingException uee) {
bytes = s.getBytes();
}
return decode(bytes, 0, bytes.length);
}
}