Base64 加密算法(6)

            b1 = decodingTable[data.charAt(data.length() - 4)];
            b2 = decodingTable[data.charAt(data.length() - 3)];
            b3 = decodingTable[data.charAt(data.length() - 2)];
            b4 = decodingTable[data.charAt(data.length() - 1)];
            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }
        return bytes;
    }
    private static byte[] discardNonBase64Bytes(byte[] data) {
        byte[] temp = new byte[data.length];
        int bytesCopied = 0;
        for (int i = 0; i < data.length; i++) {
            if (isValidBase64Byte(data[i])) {
                temp[bytesCopied++] = data[i];
            }
        }
        byte[] newData = new byte[bytesCopied];
        System.arraycopy(temp, 0, newData, 0, bytesCopied);
        return newData;
    }
    private static String discardNonBase64Chars(String data) {
        StringBuffer sb = new StringBuffer();
        int length = data.length();
        for (int i = 0; i < length; i++) {
            if (isValidBase64Byte((byte) (data.charAt(i)))) {
                sb.append(data.charAt(i));
            }
        }
        return sb.toString();
    }
    private static boolean isValidBase64Byte(byte b) {
        if (b == '=') {
            return true;
        } else if ((b < 0) || (b >= 128)) {