Java Byte Array to Base64 byteArrayToBase64(byte[] a)

Description

Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).

License

Open Source License

Declaration

public static String byteArrayToBase64(byte[] a) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    /**//  w  ww . j av  a 2s  .  c  o m
     * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
     * equivalents as specified in Table 1 of RFC 2045.
     */
    private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
            'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2',
            '3', '4', '5', '6', '7', '8', '9', '+', '/' };
    /**
     * This array is a lookup table that translates 6-bit positive integer index values into their
     * "Alternate Base64 Alphabet" equivalents. This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. This
     * alternate alphabet does not use the capital letters. It is designed for use in environments where "case folding"
     * occurs.
     */
    private static final char intToAltBase64[] = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',
            ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
            'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2',
            '3', '4', '5', '6', '7', '8', '9', '+', '?' };

    /**
     * Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).
     */
    public static String byteArrayToBase64(byte[] a) {
        return byteArrayToBase64(a, false);
    }

    private static String byteArrayToBase64(byte[] a, boolean alternate) {
        int aLen = a.length;
        int numFullGroups = aLen / 3;
        int numBytesInPartialGroup = aLen - 3 * numFullGroups;
        int resultLen = 4 * ((aLen + 2) / 3);
        StringBuilder result = new StringBuilder(resultLen);
        char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

        // Translate all full groups from byte array elements to Base64
        int inCursor = 0;
        for (int i = 0; i < numFullGroups; i++) {
            int byte0 = a[inCursor++] & 0xff;
            int byte1 = a[inCursor++] & 0xff;
            int byte2 = a[inCursor++] & 0xff;
            result.append(intToAlpha[byte0 >> 2]);
            result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
            result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
            result.append(intToAlpha[byte2 & 0x3f]);
        }

        // Translate partial group if present
        if (numBytesInPartialGroup != 0) {
            int byte0 = a[inCursor++] & 0xff;
            result.append(intToAlpha[byte0 >> 2]);
            if (numBytesInPartialGroup == 1) {
                result.append(intToAlpha[(byte0 << 4) & 0x3f]);
                result.append("==");
            } else {
                // assert numBytesInPartialGroup == 2;
                int byte1 = a[inCursor++] & 0xff;
                result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
                result.append(intToAlpha[(byte1 << 2) & 0x3f]);
                result.append('=');
            }
        }
        // assert inCursor == a.length;
        // assert result.length() == resultLen;
        return result.toString();
    }
}

Related

1. bytesToBase64(byte[] bytes)
2. bytesToBase64(byte[] bytes, int length)
3. byteToBase64(byte[] data)