guava/src/com/google/common/math/LongMath.java
@GwtIncompatible // TODO
  @SuppressWarnings("fallthrough")
  public static long divide(long p, long q, RoundingMode mode) {
    checkNotNull(mode);
    long div = p / q; // throws if q == 0
    long rem = p - q * div; // equals p % q

    if (rem == 0) {
      return div;
    }

    /*
     * Normal Java division rounds towards 0, consistently with RoundingMode.DOWN. We just have to
     * deal with the cases where rounding towards 0 is wrong, which typically depends on the sign of
     * p / q.
     *
     * signum is 1 if p and q are both nonnegative or both negative, and -1 otherwise.
     */
    int signum = 1 | (int) ((p ^ q) >> (Long.SIZE - 1));
    boolean increment;
    switch (mode) {
      case UNNECESSARY:
        checkRoundingUnnecessary(rem == 0);
        // fall through
      case DOWN:
        increment = false;
        break;
      case UP:
        increment = true;
        break;
      case CEILING:
        increment = signum > 0;
        break;
      case FLOOR:
        increment = signum < 0;
        break;
      case HALF_EVEN:
      case HALF_DOWN:
      case HALF_UP:
        long absRem = abs(rem);
        long cmpRemToHalfDivisor = absRem - (abs(q) - absRem);
        // subtracting two nonnegative longs can't overflow
        // cmpRemToHalfDivisor has the same sign as compare(abs(rem), abs(q) / 2).
        if (cmpRemToHalfDivisor == 0) { // exactly on the half mark
          increment = (mode == HALF_UP | (mode == HALF_EVEN & (div & 1) != 0));
        } else {
          increment = cmpRemToHalfDivisor > 0; // closer to the UP value
        }
        break;
      default:
        throw new AssertionError();
    }
    return increment ? div + signum : div;
  }
@GwtIncompatible // TODO
  @SuppressWarnings("fallthrough")
  public static long divide(long p, long q, RoundingMode mode) {
    checkNotNull(mode);
    long div = p / q; // throws if q == 0
    long rem = p - q * div; // equals p % q

    if (rem == 0) {
      return div;
    }

    /*
     * Normal Java division rounds towards 0, consistently with RoundingMode.DOWN. We just have to
     * deal with the cases where rounding towards 0 is wrong, which typically depends on the sign of
     * p / q.
     *
     * signum is 1 if p and q are both nonnegative or both negative, and -1 otherwise.
     */
    int signum = 1 | (int) ((p ^ q) >> (Long.SIZE - 1));
    boolean increment;
    switch (mode) {
      case UNNECESSARY:
        checkRoundingUnnecessary(rem == 0);
        // fall through
      case DOWN:
        increment = false;
        break;
      case UP:
        increment = true;
        break;
      case CEILING:
        increment = signum > 0;
        break;
      case FLOOR:
        increment = signum < 0;
        break;
      case HALF_EVEN:
      case HALF_DOWN:
      case HALF_UP:
        long absRem = abs(rem);
        long cmpRemToHalfDivisor = absRem - (abs(q) - absRem);
        // subtracting two nonnegative longs can't overflow
        // cmpRemToHalfDivisor has the same sign as compare(abs(rem), abs(q) / 2).
        if (cmpRemToHalfDivisor == 0) { // exactly on the half mark
          increment = (mode == HALF_UP | (mode == HALF_EVEN & (div & 1) != 0));
        } else {
          increment = cmpRemToHalfDivisor > 0; // closer to the UP value
        }
        break;
      default:
        throw new AssertionError();
    }
    return increment ? div + signum : div;
  }
@ GwtIncompatible // TODO @ SuppressWarnings ( "fallthrough" ) public static long divide ( long p , long q , RoundingMode mode ) { checkNotNull ( mode ) ; long div = p / q ; // throws if q == 0 long rem = p - q * div ; // equals p % q if ( rem == 0 ) { return div ; } /*
     * Normal Java division rounds towards 0, consistently with RoundingMode.DOWN. We just have to
     * deal with the cases where rounding towards 0 is wrong, which typically depends on the sign of
     * p / q.
     *
     * signum is 1 if p and q are both nonnegative or both negative, and -1 otherwise.
     */ int signum = 1 | ( int ) ( ( p ^ q ) >> ( Long . SIZE - 1 ) ) ; boolean increment ; switch ( mode ) { case UNNECESSARY : checkRoundingUnnecessary ( rem == 0 ) ; // fall through case DOWN : increment = false ; break ; case UP : increment = true ; break ; case CEILING : increment = signum > 0 ; break ; case FLOOR : increment = signum < 0 ; break ; case HALF_EVEN : case HALF_DOWN : case HALF_UP : long absRem = abs ( rem ) ; long cmpRemToHalfDivisor = absRem - ( abs ( q ) - absRem ) ; // subtracting two nonnegative longs can't overflow // cmpRemToHalfDivisor has the same sign as compare(abs(rem), abs(q) / 2). if ( cmpRemToHalfDivisor == 0 ) { // exactly on the half mark increment = ( mode == HALF_UP | ( mode == HALF_EVEN & ( div & 1 ) != 0 ) ) ; } else { increment = cmpRemToHalfDivisor > 0 ; // closer to the UP value } break ; default : throw new AssertionError ( ) ; } return increment ? div + signum : div ; }
Returns the result of dividing {@code p} by {@code q}, rounding using the specified {@code
RoundingMode}.

@throws ArithmeticException if {@code q == 0}, or if {@code mode == UNNECESSARY} and {@code a}
is not an integer multiple of {@code b}
Returns the result of dividing { @code p } by { @code q } rounding using the specified { @code RoundingMode } .