Here you can find the source of decode(byte[] source)
| Parameter | Description |
|---|---|
| source | The Base64 encoded data |
public static byte[] decode(byte[] source) throws java.io.IOException
//package com.java2s; //License from project: Open Source License public class Main { /** No options specified. Value is zero. */ public final static int NO_OPTIONS = 0; /** Specify that gzipped data should <em>not</em> be automatically gunzipped. */ public final static int DONT_GUNZIP = 4; /**/* ww w. java2 s. 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) '='; /** Preferred encoding. */ private final static String PREFERRED_ENCODING = "US-ASCII"; private final static byte WHITE_SPACE_ENC = -5; private final static byte EQUALS_SIGN_ENC = -1; /** * 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 Base64Util. */ 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 Base64Util. */ 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 }; /** * Low-level access to decoding ASCII characters in * the form of a byte array. <strong>Ignores GUNZIP option, if * it's set.</strong> This is not generally a recommended method, * although it is used internally as part of the decoding process. * Special case: if len = 0, an empty array is returned. Still, * if you need more speed and reduced memory footprint (and aren't * gzipping), consider this method. * * @param source The Base64 encoded data * @return decoded data * @since 2.3.1 */ public static byte[] decode(byte[] source) throws java.io.IOException { byte[] decoded = null; // try { decoded = decode(source, 0, source.length, NO_OPTIONS); // } catch( java.io.IOException ex ) { // assert false : "IOExceptions only come from GZipping, which is turned off: " + ex.getMessage(); // } return decoded; } /** * Low-level access to decoding ASCII characters in * the form of a byte array. <strong>Ignores GUNZIP option, if * it's set.</strong> This is not generally a recommended method, * although it is used internally as part of the decoding process. * Special case: if len = 0, an empty array is returned. Still, * if you need more speed and reduced memory footprint (and aren't * gzipping), consider this method. * * @param source The Base64 encoded data * @param off The offset of where to begin decoding * @param len The length of characters to decode * @param options Can specify options such as alphabet type to use * @return decoded data * @throws java.io.IOException If bogus characters exist in source data * @since 1.3 */ public static byte[] decode(byte[] source, int off, int len, int options) throws java.io.IOException { // Lots of error checking and exception throwing if (source == null) { throw new NullPointerException("Cannot decode null source array."); } // end if if (off < 0 || off + len > source.length) { throw new IllegalArgumentException( String.format("Source array with length %d cannot have offset of %d and process %d bytes.", source.length, off, len)); } // end if if (len == 0) { return new byte[0]; } else if (len < 4) { throw new IllegalArgumentException( "Base64-encoded string must have at least four characters, but length specified was " + len); } // end if byte[] DECODABET = getDecodabet(options); int len34 = len * 3 / 4; // Estimate on array size byte[] outBuff = new byte[len34]; // Upper limit on size of output int outBuffPosn = 0; // Keep track of where we're writing byte[] b4 = new byte[4]; // Four byte buffer from source, eliminating white space int b4Posn = 0; // Keep track of four byte input buffer int i = 0; // Source array counter byte sbiDecode = 0; // Special value from DECODABET for (i = off; i < off + len; i++) { // Loop through source sbiDecode = DECODABET[source[i] & 0xFF]; // White space, Equals sign, or legit Base64 character // Note the values such as -5 and -9 in the // DECODABETs at the top of the file. if (sbiDecode >= WHITE_SPACE_ENC) { if (sbiDecode >= EQUALS_SIGN_ENC) { b4[b4Posn++] = source[i]; // Save non-whitespace if (b4Posn > 3) { // Time to decode? outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn, options); b4Posn = 0; // If that was the equals sign, break out of 'for' loop if (source[i] == EQUALS_SIGN) { break; } // end if: equals sign } // end if: quartet built } // end if: equals sign or better } // end if: white space, equals sign or better else { // There's a bad input character in the Base64 stream. throw new java.io.IOException(String .format("Bad Base64 input character decimal %d in array position %d", source[i] & 0xFF, i)); } // end else: } // each input character byte[] out = new byte[outBuffPosn]; System.arraycopy(outBuff, 0, out, 0, outBuffPosn); return out; } /** * Decodes data from Base64 notation, automatically * detecting gzip-compressed data and decompressing it. * * @param s the string to decode * @return the decoded data * @throws java.io.IOException If there is a problem * @since 1.4 */ public static byte[] decode(String s) throws java.io.IOException { return decode(s, NO_OPTIONS); } /** * Decodes data from Base64 notation, automatically * detecting gzip-compressed data and decompressing it. * * @param s the string to decode * @param options encode options such as URL_SAFE * @return the decoded data * @throws java.io.IOException if there is an error * @throws NullPointerException if <tt>s</tt> is null * @since 1.4 */ public static byte[] decode(String s, int options) throws java.io.IOException { if (s == null) { throw new NullPointerException("Input string was null."); } // end if byte[] bytes; try { bytes = s.getBytes(PREFERRED_ENCODING); } // end try catch (java.io.UnsupportedEncodingException uee) { bytes = s.getBytes(); } // end catch //</change> // Decode bytes = decode(bytes, 0, bytes.length, options); // Check to see if it's gzip-compressed // GZIP Magic Two-Byte Number: 0x8b1f (35615) boolean dontGunzip = (options & DONT_GUNZIP) != 0; if ((bytes != null) && (bytes.length >= 4) && (!dontGunzip)) { int head = (bytes[0] & 0xff) | ((bytes[1] << 8) & 0xff00); if (java.util.zip.GZIPInputStream.GZIP_MAGIC == head) { java.io.ByteArrayInputStream bais = null; java.util.zip.GZIPInputStream gzis = null; java.io.ByteArrayOutputStream baos = null; byte[] buffer = new byte[2048]; int length = 0; try { baos = new java.io.ByteArrayOutputStream(); bais = new java.io.ByteArrayInputStream(bytes); gzis = new java.util.zip.GZIPInputStream(bais); while ((length = gzis.read(buffer)) >= 0) { baos.write(buffer, 0, length); } // end while: reading input // No error? Get new bytes. bytes = baos.toByteArray(); } // end try catch (java.io.IOException e) { e.printStackTrace(); // Just return originally-decoded bytes } // end catch finally { try { baos.close(); } catch (Exception e) { } try { gzis.close(); } catch (Exception e) { } try { bais.close(); } catch (Exception e) { } } // end finally } // end if: gzipped } // end if: bytes.length >= 2 return bytes; } /** * 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; } } /** * 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; } } }