public static String base64encode(byte[] buf) {
        int size = buf.length;
        char[] ar = new char[((size + 2) / 3) * 4];
        int a = 0;
        int i = 0;
        while (i < size) {
            byte b0 = buf[i++];
            byte b1 = (i < size) ? buf[i++] : 0;
            byte b2 = (i < size) ? buf[i++] : 0;

            int mask = 0x3F;
            ar[a++] = ALPHABET[(b0 >> 2) & mask];
            ar[a++] = ALPHABET[((b0 << 4) | ((b1 & 0xFF) >> 4)) & mask];
            ar[a++] = ALPHABET[((b1 << 2) | ((b2 & 0xFF) >> 6)) & mask];
            ar[a++] = ALPHABET[b2 & mask];
        }
        switch (size % 3) {
            case 1:
                ar[--a] = '=';
            case 2:
                ar[--a] = '=';
        }
        return new String(ar);
    }