code: private static byte[] encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes, int options) {
          encode3to4(threeBytes, 0, numSigBytes, b4, 0, options);
          return b4;
      }
docs: Encodes up to the first three bytes of array <var>threeBytes</var> and returns a four-byte array in Base64 notation. The
  actual number of significant bytes in your array is given by <var>numSigBytes</var>. The array <var>threeBytes</var>
  needs only be as big as <var>numSigBytes</var>. Code can reuse a byte array by passing a four-byte array as
  <var>b4</var>.
  
  @param b4 A reusable byte array to reduce array instantiation
  @param threeBytes the array to convert
  @param numSigBytes the number of significant bytes in your array
  @return four byte array in Base64 notation.
  @since 1.5.1