Encodes up to three bytes of the array source * and writes the resulting four Base64 bytes to destination. * The source and destination arrays can be manipulated * anywhere along their length by specifying * srcOffset and destOffset. * This method does not check to make sure your arrays * are large enough to accomodate srcOffset + 3 for * the source array or destOffset + 4 for * the destination array. * The actual number of significant bytes in your array is * given by numSigBytes.
*This is the lowest level of the encoding methods with * all possible parameters.
* * @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 * @return the destination array * @since 1.3 */ private static byte[] encode3to4( byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset, int options ) { byte[] ALPHABET = getAlphabet( options ); // 1 2 3 // 01234567890123456789012345678901 Bit position // --------000000001111111122222222 Array position from threeBytes // --------| || || || | Six bit groups to index ALPHABET // >>18 >>12 >> 6 >> 0 Right shift necessary // 0x3f 0x3f 0x3f Additional AND // Create buffer with zero-padding if there are only one or two // significant bytes passed in the array. // 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 to an int. int inBuff = ( numSigBytes > 0 ? ((source[ srcOffset ] << 24) >>> 8) : 0 ) | ( numSigBytes > 1 ? ((source[ srcOffset + 1 ] << 24) >>> 16) : 0 ) | ( numSigBytes > 2 ? ((source[ srcOffset + 2 ] << 24) >>> 24) : 0 ); switch( numSigBytes ) { case 3: destination[ destOffset ] = ALPHABET[ (inBuff >>> 18) ]; destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ]; destination[ destOffset + 2 ] = ALPHABET[ (inBuff >>> 6) & 0x3f ]; destination[ destOffset + 3 ] = ALPHABET[ (inBuff ) & 0x3f ]; return destination; case 2: destination[ destOffset ] = ALPHABET[ (inBuff >>> 18) ]; destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ]; destination[ destOffset + 2 ] = ALPHABET[ (inBuff >>> 6) & 0x3f ]; destination[ destOffset + 3 ] = EQUALS_SIGN; return destination; case 1: destination[ destOffset ] = ALPHABET[ (inBuff >>> 18) ]; destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ]; destination[ destOffset + 2 ] = EQUALS_SIGN; destination[ destOffset + 3 ] = EQUALS_SIGN; return destination; default: return destination; } // end switch } // end encode3to4 /** * Encodes a byte array into Base64 notation. * Does not GZip-compress data. * * @param source The data to convert * @return The data in Base64-encoded form * @throws NullPointerException if source array is null * @since 1.4 */ public static String encodeBytes( byte[] source ) { // Since we're not going to have the GZIP encoding turned on, // we're not going to have an java.io.IOException thrown, so // we should not force the user to have to catch it. String encoded = null; try { encoded = encodeBytes(source, 0, source.length, NO_OPTIONS); } catch (java.io.IOException ex) { assert false : ex.getMessage(); } // end catch assert encoded != null; return encoded; } /** * 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 * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#GZIP * @see Base64#DO_BREAK_LINES * @throws java.io.IOException if there is an error * @throws NullPointerException if source array is null * @throws IllegalArgumentException if source array, offset, or length are invalid * @since 2.0 */ public static String encodeBytes( byte[] source, int off, int len, int options ) throws java.io.IOException { byte[] encoded = encodeBytesToBytes( source, off, len, options ); // Return value according to relevant encoding. try { return new String( encoded, PREFERRED_ENCODING ); } // end try catch (java.io.UnsupportedEncodingException uue) { return new String( encoded ); } // end catch } /** * Similar to {@link #encodeBytes(byte[], int, int, int)} but returns * a byte array instead of instantiating a String. This is more efficient * if you're working with I/O streams and have large data sets to encode. * * * @param source The data to convert * @param off Offset in array where conversion should begin * @param len Length of data to convert * @param options Specified options * @return The Base64-encoded data as a String * @see Base64#GZIP * @see Base64#DO_BREAK_LINES * @throws java.io.IOException if there is an error * @throws NullPointerException if source array is null * @throws IllegalArgumentException if source array, offset, or length are invalid * @since 2.3.1 */ public static byte[] encodeBytesToBytes( byte[] source, int off, int len, int options ) throws java.io.IOException { if( source == null ){ throw new NullPointerException( "Cannot serialize a null array." ); } // end if: null if( off < 0 ){ throw new IllegalArgumentException( "Cannot have negative offset: " + off ); } // end if: off < 0 if( len < 0 ){ throw new IllegalArgumentException( "Cannot have length offset: " + len ); } // end if: len < 0 if( off + len > source.length ){ throw new IllegalArgumentException( String.format( "Cannot have offset of %d and length of %d with array of length %d", off,len,source.length)); } // end if: off < 0 boolean breakLines = (options & DO_BREAK_LINES) != 0; //int len43 = len * 4 / 3; //byte[] outBuff = new byte[ ( len43 ) // Main 4:3 // + ( (len % 3) > 0 ? 4 : 0 ) // Account for padding // + (breakLines ? ( len43 / MAX_LINE_LENGTH ) : 0) ]; // New lines // Try to determine more precisely how big the array needs to be. // If we get it right, we don't have to do an array copy, and // we save a bunch of memory. int encLen = ( len / 3 ) * 4 + ( len % 3 > 0 ? 4 : 0 ); // Bytes needed for actual encoding if( breakLines ){ encLen += encLen / MAX_LINE_LENGTH; // Plus extra newline characters } byte[] outBuff = new byte[ encLen ]; int d = 0; int e = 0; int len2 = len - 2; int lineLength = 0; for( ; d < len2; d+=3, e+=4 ) { encode3to4( source, d+off, 3, outBuff, e, options ); lineLength += 4; if( breakLines && lineLength >= MAX_LINE_LENGTH ) { outBuff[e+4] = NEW_LINE; e++; lineLength = 0; } // end if: end of line } // en dfor: each piece of array if( d < len ) { encode3to4( source, d+off, len - d, outBuff, e, options ); e += 4; } // end if: some padding needed // Only resize array if we didn't guess it right. if( e <= outBuff.length - 1 ){ // If breaking lines and the last byte falls right at // the line length (76 bytes per line), there will be // one extra byte, and the array will need to be resized. // Not too bad of an estimate on array size, I'd say. byte[] finalOut = new byte[e]; System.arraycopy(outBuff,0, finalOut,0,e); //System.err.println("Having to resize array from " + outBuff.length + " to " + e ); return finalOut; } else { //System.err.println("No need to resize array."); return outBuff; } } }