Android Byte Array Decode decodeWebSafe(String s)

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  5. decodeWebSafe(String s)

Description

Decodes data from web safe Base64 notation.

License

Apache License

Parameter

Parameter Description
s the string to decode (decoded in default encoding)

Return

the decoded data

Declaration 

public static byte[] decodeWebSafe(String s)
        throws Base64DecoderException

Method Source Code

// Licensed under the Apache License, Version 2.0 (the "License");


public class Main{
    /** 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';
    /**//from w  ww . ja  v a2 s.  co m
     * 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 */
    };
    private final static byte WHITE_SPACE_ENC = -5;
    private final static byte EQUALS_SIGN_ENC = -1;
    /**
     * 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 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 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 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 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 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 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;
    }
    /**
     * 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;
        }
    }
}

Related

  1. decode(byte[] source, int off, int len, byte[] decodabet)
  2. decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset, byte[] decodabet)
  3. decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset, byte[] decodabet)
  4. decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset, byte[] decodabet)
  5. decodeWebSafe(String s)
  6. decodeWebSafe(byte[] source)
  7. decodeWebSafe(byte[] source)
  8. decodeWebSafe(byte[] source)
  9. decodeWebSafe(byte[] source, int off, int len)