Method remainder

output/java_guava/1.4.19/UnsignedLongs.java:236–260

Returns dividend % divisor, where the dividend and divisor are treated as unsigned 64-bit quantities. @param dividend the dividend (numerator) @param divisor the divisor (denominator) @throws ArithmeticException if divisor is 0 @since 11.0

(long dividend, long divisor)

  public static long remainder(long dividend, long divisor) {
    if (divisor < 0) { // i.e., divisor >= 2^63:
      if (compare(dividend, divisor) < 0) {
        return dividend; // dividend < divisor
      } else {
        return dividend - divisor; // dividend >= divisor
      }
    }

    // Optimization - use signed modulus if dividend < 2^63
    if (dividend >= 0) {
      return dividend % divisor;
    }

    /*
     * Otherwise, approximate the quotient, check, and correct if necessary. Our approximation is
     * guaranteed to be either exact or one less than the correct value. This follows from fact that
     * floor(floor(x)/i) == floor(x/i) for any real x and integer i != 0. The proof is not quite
     * trivial.
     */

    long quotient = ((dividend >>> 1) / divisor) << 1;
    long rem = dividend - quotient * divisor;
    return rem - (compare(rem, divisor) >= 0 ? divisor : 0);
  }

  /**
   * Returns the unsigned {@code long} value represented by the given decimal string.