Description
Decodes four bytes from array
source and writes the resulting bytes (up to three of them) to
destination.
Parameter
| Parameter | Description |
|---|
| source | the array to convert |
| srcOffset | the index where conversion begins |
| destination | the array to hold the conversion |
| destOffset | the index where output will be put |
| options | alphabet type is pulled from this (standard, url-safe, ordered) |
Exception
| Parameter | Description |
|---|
| NullPointerException | if source or destination arrays are null |
| IllegalArgumentException | if srcOffset or destOffset are invalidor there is not enough room in the array. |
Return
the number of decoded bytes converted
Declaration
private static int decode4to3(byte[] source, int srcOffset,
byte[] destination, int destOffset, int options)
Method Source Code
//package com.java2s;
public class Main {
/**//www.j a v a2s .c o m
* Encode using Base64-like encoding that is URL- and Filename-safe as described
* in Section 4 of RFC3548:
* <a href="http://www.faqs.org/rfcs/rfc3548.html">http://www.faqs.org/rfcs/rfc3548.html</a>.
* It is important to note that data encoded this way is <em>not</em> officially valid Base64,
* or at the very least should not be called Base64 without also specifying that is
* was encoded using the URL- and Filename-safe dialect.
*/
public final static int URL_SAFE = 16;
/**
* Encode using the special "ordered" dialect of Base64 described here:
* <a href="http://www.faqs.org/qa/rfcc-1940.html">http://www.faqs.org/qa/rfcc-1940.html</a>.
*/
public final static int ORDERED = 32;
/** The equals sign (=) as a byte. */
private final static byte EQUALS_SIGN = (byte) '=';
/**
* Translates a Base64 value to either its 6-bit reconstruction value
* or a negative number indicating some other meaning.
**/
private final static byte[] _STANDARD_DECODABET = { -9, -9, -9, -9, -9,
-9, -9, -9, -9, // Decimal 0 - 8
-5, -5, // Whitespace: Tab and Linefeed
-9, -9, // Decimal 11 - 12
-5, // Whitespace: Carriage Return
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26
-9, -9, -9, -9, -9, // Decimal 27 - 31
-5, // Whitespace: Space
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42
62, // Plus sign at decimal 43
-9, -9, -9, // Decimal 44 - 46
63, // Slash at decimal 47
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine
-9, -9, -9, // Decimal 58 - 60
-1, // Equals sign at decimal 61
-9, -9, -9, // Decimal 62 - 64
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A' through 'N'
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O' through 'Z'
-9, -9, -9, -9, -9, -9, // Decimal 91 - 96
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a' through 'm'
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n' through 'z'
-9, -9, -9, -9, -9 // Decimal 123 - 127
, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 128 - 139
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 140 - 152
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 153 - 165
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 166 - 178
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 179 - 191
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 192 - 204
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 205 - 217
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 218 - 230
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 231 - 243
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9 // Decimal 244 - 255
};
/**
* Used in decoding URL- and Filename-safe dialects of Base64.
*/
private final static byte[] _URL_SAFE_DECODABET = { -9, -9, -9, -9, -9,
-9, -9, -9, -9, // Decimal 0 - 8
-5, -5, // Whitespace: Tab and Linefeed
-9, -9, // Decimal 11 - 12
-5, // Whitespace: Carriage Return
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26
-9, -9, -9, -9, -9, // Decimal 27 - 31
-5, // Whitespace: Space
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42
-9, // Plus sign at decimal 43
-9, // Decimal 44
62, // Minus sign at decimal 45
-9, // Decimal 46
-9, // Slash at decimal 47
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine
-9, -9, -9, // Decimal 58 - 60
-1, // Equals sign at decimal 61
-9, -9, -9, // Decimal 62 - 64
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A' through 'N'
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O' through 'Z'
-9, -9, -9, -9, // Decimal 91 - 94
63, // Underscore at decimal 95
-9, // Decimal 96
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a' through 'm'
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n' through 'z'
-9, -9, -9, -9, -9 // Decimal 123 - 127
, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 128 - 139
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 140 - 152
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 153 - 165
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 166 - 178
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 179 - 191
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 192 - 204
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 205 - 217
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 218 - 230
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 231 - 243
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9 // Decimal 244 - 255
};
/**
* Used in decoding the "ordered" dialect of Base64.
*/
private final static byte[] _ORDERED_DECODABET = { -9, -9, -9, -9, -9,
-9, -9, -9, -9, // Decimal 0 - 8
-5, -5, // Whitespace: Tab and Linefeed
-9, -9, // Decimal 11 - 12
-5, // Whitespace: Carriage Return
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 - 26
-9, -9, -9, -9, -9, // Decimal 27 - 31
-5, // Whitespace: Space
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42
-9, // Plus sign at decimal 43
-9, // Decimal 44
0, // Minus sign at decimal 45
-9, // Decimal 46
-9, // Slash at decimal 47
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, // Numbers zero through nine
-9, -9, -9, // Decimal 58 - 60
-1, // Equals sign at decimal 61
-9, -9, -9, // Decimal 62 - 64
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // Letters 'A' through 'M'
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, // Letters 'N' through 'Z'
-9, -9, -9, -9, // Decimal 91 - 94
37, // Underscore at decimal 95
-9, // Decimal 96
38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, // Letters 'a' through 'm'
51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, // Letters 'n' through 'z'
-9, -9, -9, -9, -9 // Decimal 123 - 127
, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 128 - 139
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 140 - 152
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 153 - 165
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 166 - 178
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 179 - 191
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 192 - 204
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 205 - 217
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 218 - 230
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 231 - 243
-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9 // Decimal 244 - 255
};
/**
* 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 accomodate <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.
* <p>This is the lowest level of the decoding methods with
* all possible parameters.</p>
*
*
* @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
* @param options alphabet type is pulled from this (standard, url-safe, ordered)
* @return the number of decoded bytes converted
* @throws NullPointerException if source or destination arrays are null
* @throws IllegalArgumentException if srcOffset or destOffset are invalid
* or there is not enough room in the array.
* @since 1.3
*/
private static int decode4to3(byte[] source, int srcOffset,
byte[] destination, int destOffset, int options) {
// Lots of error checking and exception throwing
if (source == null) {
throw new NullPointerException("Source array was null.");
} // end if
if (destination == null) {
throw new NullPointerException("Destination array was null.");
} // end if
if (srcOffset < 0 || srcOffset + 3 >= source.length) {
throw new IllegalArgumentException(
String.format(
"Source array with length %d cannot have offset of %d and still process four bytes.",
source.length, srcOffset));
} // end if
if (destOffset < 0 || destOffset + 2 >= destination.length) {
throw new IllegalArgumentException(
String.format(
"Destination array with length %d cannot have offset of %d and still store three bytes.",
destination.length, destOffset));
} // end if
byte[] DECODABET = getDecodabet(options);
// Example: Dk==
if (source[srcOffset + 2] == EQUALS_SIGN) {
// Two ways to do the same thing. Don't know which way I like best.
//int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
// | ( ( DECODABET[ source[ srcOffset + 1] ] << 24 ) >>> 12 );
int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
| ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12);
destination[destOffset] = (byte) (outBuff >>> 16);
return 1;
}
// Example: DkL=
else if (source[srcOffset + 3] == EQUALS_SIGN) {
// Two ways to do the same thing. Don't know which way I like best.
//int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
// | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
// | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 );
int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
| ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
| ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6);
destination[destOffset] = (byte) (outBuff >>> 16);
destination[destOffset + 1] = (byte) (outBuff >>> 8);
return 2;
}
// Example: DkLE
else {
// Two ways to do the same thing. Don't know which way I like best.
//int outBuff = ( ( DECODABET[ source[ srcOffset ] ] << 24 ) >>> 6 )
// | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
// | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 )
// | ( ( DECODABET[ source[ srcOffset + 3 ] ] << 24 ) >>> 24 );
int outBuff = ((DECODABET[source[srcOffset]] & 0xFF) << 18)
| ((DECODABET[source[srcOffset + 1]] & 0xFF) << 12)
| ((DECODABET[source[srcOffset + 2]] & 0xFF) << 6)
| ((DECODABET[source[srcOffset + 3]] & 0xFF));
destination[destOffset] = (byte) (outBuff >> 16);
destination[destOffset + 1] = (byte) (outBuff >> 8);
destination[destOffset + 2] = (byte) (outBuff);
return 3;
}
}
/**
* Returns one of the _SOMETHING_DECODABET byte arrays depending on
* the options specified.
* It's possible, though silly, to specify ORDERED and URL_SAFE
* in which case one of them will be picked, though there is
* no guarantee as to which one will be picked.
*/
private final static byte[] getDecodabet(int options) {
if ((options & URL_SAFE) == URL_SAFE) {
return _URL_SAFE_DECODABET;
} else if ((options & ORDERED) == ORDERED) {
return _ORDERED_DECODABET;
} else {
return _STANDARD_DECODABET;
}
}
}
Related
- decodeWebSafe(byte[] source)
- decodeWebSafe(byte[] source)
- decodeWebSafe(byte[] source, int off, int len)
- decodeWebSafe(byte[] source, int off, int len)
- decodeWebSafe(byte[] source, int off, int len)
- getDecodabet(int options)