Android Base64 Byte Array Encode encodeWebSafe(byte[] source, boolean doPadding)

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Description

Encodes a byte array into web safe Base64 notation.

Parameter

Parameter Description
source The data to convert
doPadding is true to pad result with '=' chars if it does not fall on 3 byte boundaries

Declaration 

public static String encodeWebSafe(byte[] source, boolean doPadding)

Method Source Code

//package com.java2s;

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.  jav  a2  s. com*/
     * 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) '_' };

    /**
     * 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.
     * 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 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;
    }

    /**
     * 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
    }
}

Related

  1. encode(byte[] bytes)
  2. encode(byte[] data)
  3. encode(byte[] arr)
  4. encode(byte[] data)
  5. encode(byte[] bytes)
  6. encode(byte[] data)
  7. encodeBase64Byte(byte base64Byte)
  8. encodeLast2Bytes(byte bytes[])