In-App purchasing demo | Qt 6.4

- Qt 6.4
- In-App purchasing demo
- Qt 6.4.1 Reference Documentation

# In-App purchasing demo

     /* Copyright (c) 2012 Google Inc.
      * Copyright (c) 2015 The Qt Company Ltd.
      *
      * Licensed under the Apache License, Version 2.0 (the "License");
      * you may not use this file except in compliance with the License.
      * You may obtain a copy of the License at
      *
      *     http://www.apache.org/licenses/LICENSE-2.0
      *
      * Unless required by applicable law or agreed to in writing, software
      * distributed under the License is distributed on an "AS IS" BASIS,
      * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      * See the License for the specific language governing permissions and
      * limitations under the License.
      */

     package org.qtproject.qt.android.purchasing;

     // This code was converted from code at http://iharder.sourceforge.net/base64/
     // Lots of extraneous features were removed.
     /* The original code said:
      * <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/xmlizable">http://iharder.net/xmlizable</a>
      * periodically to check for updates or to contribute improvements.
      * </p>
      *
      * @author Robert Harder
      * @author rharder@usa.net
      * @version 1.3
      */

     /**
      * Base64 converter class. This code is not a complete MIME encoder;
      * it simply converts binary data to base64 data and back.
      *
      * <p>Note {@link CharBase64} is a GWT-compatible implementation of this
      * class.
      */
     public class Base64 {
         /** Specify encoding (value is {@code true}). */
         public final static boolean ENCODE = true;

         /** Specify decoding (value is {@code false}). */
         public final static boolean DECODE = false;

         /** The equals sign (=) as a byte. */
         private final static byte EQUALS_SIGN = (byte) '=';

         /** The new line character (\n) as a byte. */
         private final static byte NEW_LINE = (byte) '\n';

         /**
          * The 64 valid Base64 values.
          */
         private final static byte[] ALPHABET =
             {(byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
             (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K',
             (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P',
             (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
             (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
             (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
             (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j',
             (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o',
             (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't',
             (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
             (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3',
             (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8',
             (byte) '9', (byte) '+', (byte) '/'};

         /**
          * The 64 valid web safe Base64 values.
          */
         private final static byte[] WEBSAFE_ALPHABET =
             {(byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
             (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K',
             (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P',
             (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
             (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
             (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
             (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j',
             (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o',
             (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't',
             (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
             (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3',
             (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8',
             (byte) '9', (byte) '-', (byte) '_'};

         /**
          * Translates a Base64 value to either its 6-bit reconstruction value
          * or a negative number indicating some other meaning.
          **/
         private final static byte[] 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 */
         };

         /** The web safe decodabet */
         private final static byte[] WEBSAFE_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, -9, -9, // Decimal 33 - 44
             62, // Dash '-' sign at decimal 45
             -9, -9, // Decimal 46-47
             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 */
             };

         // Indicates white space in encoding
         private final static byte WHITE_SPACE_ENC = -5;
         // Indicates equals sign in encoding
         private final static byte EQUALS_SIGN_ENC = -1;

         /** Defeats instantiation. */
         private Base64() {
         }

         /* ********  E N C O D I N G   M E T H O D S  ******** */

         /**
          * 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
          * @param alphabet is the encoding alphabet
          * @return the <var>destination</var> array
          * @since 1.3
          */
         private static byte[] encode3to4(byte[] source, int srcOffset,
                 int numSigBytes, byte[] destination, int destOffset, byte[] alphabet) {
             //           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.
          * Equivalent to calling
          * {@code encodeBytes(source, 0, source.length)}
          *
          * @param source The data to convert
          * @since 1.4
          */
         public static String encode(byte[] source) {
             return encode(source, 0, source.length, ALPHABET, true);
         }

         /**
          * Encodes a byte array into web safe Base64 notation.
          *
          * @param source The data to convert
          * @param doPadding is {@code true} to pad result with '=' chars
          *        if it does not fall on 3 byte boundaries
          */
         public static String encodeWebSafe(byte[] source, boolean doPadding) {
             return encode(source, 0, source.length, WEBSAFE_ALPHABET, doPadding);
         }

         /**
          * 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 alphabet the encoding alphabet
          * @param doPadding is {@code true} to pad result with '=' chars
          * if it does not fall on 3 byte boundaries
          * @since 1.4
          */
         public static String encode(byte[] source, int off, int len, byte[] alphabet,
                 boolean doPadding) {
             byte[] outBuff = encode(source, off, len, alphabet, Integer.MAX_VALUE);
             int outLen = outBuff.length;

             // If doPadding is false, set length to truncate '='
             // padding characters
             while (doPadding == false && outLen > 0) {
                 if (outBuff[outLen - 1] != '=') {
                     break;
                 }
                 outLen -= 1;
             }

             return new String(outBuff, 0, outLen);
         }

         /**
          * 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 alphabet is the encoding alphabet
          * @param maxLineLength maximum length of one line.
          * @return the BASE64-encoded byte array
          */
         public static byte[] encode(byte[] source, int off, int len, byte[] alphabet,
                 int maxLineLength) {
             int lenDiv3 = (len + 2) / 3; // ceil(len / 3)
             int len43 = lenDiv3 * 4;
             byte[] outBuff = new byte[len43 // Main 4:3
                                       + (len43 / maxLineLength)]; // New lines

             int d = 0;
             int e = 0;
             int len2 = len - 2;
             int lineLength = 0;
             for (; d < len2; d += 3, e += 4) {

                 // The following block of code is the same as
                 // encode3to4( source, d + off, 3, outBuff, e, alphabet );
                 // but inlined for faster encoding (~20% improvement)
                 int inBuff =
                         ((source[d + off] << 24) >>> 8)
                         | ((source[d + 1 + off] << 24) >>> 16)
                         | ((source[d + 2 + off] << 24) >>> 24);
                 outBuff[e] = alphabet[(inBuff >>> 18)];
                 outBuff[e + 1] = alphabet[(inBuff >>> 12) & 0x3f];
                 outBuff[e + 2] = alphabet[(inBuff >>> 6) & 0x3f];
                 outBuff[e + 3] = alphabet[(inBuff) & 0x3f];

                 lineLength += 4;
                 if (lineLength == maxLineLength) {
                     outBuff[e + 4] = NEW_LINE;
                     e++;
                     lineLength = 0;
                 } // end if: end of line
             } // end for: each piece of array

             if (d < len) {
                 encode3to4(source, d + off, len - d, outBuff, e, alphabet);

                 lineLength += 4;
                 if (lineLength == maxLineLength) {
                     // Add a last newline
                     outBuff[e + 4] = NEW_LINE;
                     e++;
                 }
                 e += 4;
             }

             assert (e == outBuff.length);
             return outBuff;
         }

         /* ********  D E C O D I N G   M E T H O D S  ******** */

         /**
          * 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
          * @param decodabet the decodabet for decoding Base64 content
          * @return the number of decoded bytes converted
          * @since 1.3
          */
         private static int decode4to3(byte[] source, int srcOffset,
                 byte[] destination, int destOffset, byte[] decodabet) {
             // Example: Dk==
             if (source[srcOffset + 2] == EQUALS_SIGN) {
                 int outBuff =
                         ((decodabet[source[srcOffset]] << 24) >>> 6)
                         | ((decodabet[source[srcOffset + 1]] << 24) >>> 12);

                 destination[destOffset] = (byte) (outBuff >>> 16);
                 return 1;
             } else if (source[srcOffset + 3] == EQUALS_SIGN) {
                 // Example: DkL=
                 int outBuff =
                         ((decodabet[source[srcOffset]] << 24) >>> 6)
                         | ((decodabet[source[srcOffset + 1]] << 24) >>> 12)
                         | ((decodabet[source[srcOffset + 2]] << 24) >>> 18);

                 destination[destOffset] = (byte) (outBuff >>> 16);
                 destination[destOffset + 1] = (byte) (outBuff >>> 8);
                 return 2;
             } else {
                 // Example: DkLE
                 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);

                 destination[destOffset] = (byte) (outBuff >> 16);
                 destination[destOffset + 1] = (byte) (outBuff >> 8);
                 destination[destOffset + 2] = (byte) (outBuff);
                 return 3;
             }
         } // end decodeToBytes

         /**
          * Decodes data from Base64 notation.
          *
          * @param s the string to decode (decoded in default encoding)
          * @return the decoded data
          * @since 1.4
          */
         public static byte[] decode(String s) throws Base64DecoderException {
             byte[] bytes = s.getBytes();
             return decode(bytes, 0, bytes.length);
         }

         /**
          * Decodes data from web safe Base64 notation.
          * Web safe encoding uses '-' instead of '+', '_' instead of '/'
          *
          * @param s the string to decode (decoded in default encoding)
          * @return the decoded data
          */
         public static byte[] decodeWebSafe(String s) throws Base64DecoderException {
             byte[] bytes = s.getBytes();
             return decodeWebSafe(bytes, 0, bytes.length);
         }

         /**
          * Decodes Base64 content in byte array format and returns
          * the decoded byte array.
          *
          * @param source The Base64 encoded data
          * @return decoded data
          * @since 1.3
          * @throws Base64DecoderException
          */
         public static byte[] decode(byte[] source) throws Base64DecoderException {
             return decode(source, 0, source.length);
         }

         /**
          * Decodes web safe Base64 content in byte array format and returns
          * the decoded data.
          * Web safe encoding uses '-' instead of '+', '_' instead of '/'
          *
          * @param source the string to decode (decoded in default encoding)
          * @return the decoded data
          */
         public static byte[] decodeWebSafe(byte[] source)
                 throws Base64DecoderException {
             return decodeWebSafe(source, 0, source.length);
         }

         /**
          * Decodes Base64 content in byte array format and returns
          * the decoded 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
          * @since 1.3
          * @throws Base64DecoderException
          */
         public static byte[] decode(byte[] source, int off, int len)
                 throws Base64DecoderException {
             return decode(source, off, len, DECODABET);
         }

         /**
          * Decodes web safe Base64 content in byte array format and returns
          * the decoded byte array.
          * Web safe encoding uses '-' instead of '+', '_' instead of '/'
          *
          * @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
          */
         public static byte[] decodeWebSafe(byte[] source, int off, int len)
                 throws Base64DecoderException {
             return decode(source, off, len, WEBSAFE_DECODABET);
         }

         /**
          * Decodes Base64 content using the supplied decodabet and returns
          * the decoded 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
          * @param decodabet the decodabet for decoding Base64 content
          * @return decoded data
          */
         public static byte[] decode(byte[] source, int off, int len, byte[] decodabet)
                 throws Base64DecoderException {
             int len34 = len * 3 / 4;
             byte[] outBuff = new byte[2 + len34]; // Upper limit on size of output
             int outBuffPosn = 0;

             byte[] b4 = new byte[4];
             int b4Posn = 0;
             int i = 0;
             byte sbiCrop = 0;
             byte sbiDecode = 0;
             for (i = 0; i < len; i++) {
                 sbiCrop = (byte) (source[i + off] & 0x7f); // Only the low seven bits
                 sbiDecode = decodabet[sbiCrop];

                 if (sbiDecode >= WHITE_SPACE_ENC) { // White space Equals sign or better
                     if (sbiDecode >= EQUALS_SIGN_ENC) {
                         // An equals sign (for padding) must not occur at position 0 or 1
                         // and must be the last byte[s] in the encoded value
                         if (sbiCrop == EQUALS_SIGN) {
                             int bytesLeft = len - i;
                             byte lastByte = (byte) (source[len - 1 + off] & 0x7f);
                             if (b4Posn == 0 || b4Posn == 1) {
                                 throw new Base64DecoderException(
                                         "invalid padding byte '=' at byte offset " + i);
                             } else if ((b4Posn == 3 && bytesLeft > 2)
                                     || (b4Posn == 4 && bytesLeft > 1)) {
                                 throw new Base64DecoderException(
                                         "padding byte '=' falsely signals end of encoded value "
                                                 + "at offset " + i);
                             } else if (lastByte != EQUALS_SIGN && lastByte != NEW_LINE) {
                                 throw new Base64DecoderException(
                                         "encoded value has invalid trailing byte");
                             }
                             break;
                         }

                         b4[b4Posn++] = sbiCrop;
                         if (b4Posn == 4) {
                             outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn, decodabet);
                             b4Posn = 0;
                         }
                     }
                 } else {
                     throw new Base64DecoderException("Bad Base64 input character at " + i
                             + ": " + source[i + off] + "(decimal)");
                 }
             }

             // Because web safe encoding allows non padding base64 encodes, we
             // need to pad the rest of the b4 buffer with equal signs when
             // b4Posn != 0.  There can be at most 2 equal signs at the end of
             // four characters, so the b4 buffer must have two or three
             // characters.  This also catches the case where the input is
             // padded with EQUALS_SIGN
             if (b4Posn != 0) {
                 if (b4Posn == 1) {
                     throw new Base64DecoderException("single trailing character at offset "
                             + (len - 1));
                 }
                 b4[b4Posn++] = EQUALS_SIGN;
                 outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn, decodabet);
             }

             byte[] out = new byte[outBuffPosn];
             System.arraycopy(outBuff, 0, out, 0, outBuffPosn);
             return out;
         }
     }