148 lines
4.8 KiB
C++
148 lines
4.8 KiB
C++
// © 2017 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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#include "unicode/utypes.h"
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#if !UCONFIG_NO_FORMATTING
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#ifndef __NUMBER_ROUNDINGUTILS_H__
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#define __NUMBER_ROUNDINGUTILS_H__
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#include "number_types.h"
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U_NAMESPACE_BEGIN
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namespace number {
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namespace impl {
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namespace roundingutils {
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enum Section {
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SECTION_LOWER_EDGE = -1,
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SECTION_UPPER_EDGE = -2,
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SECTION_LOWER = 1,
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SECTION_MIDPOINT = 2,
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SECTION_UPPER = 3
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};
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/**
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* Converts a rounding mode and metadata about the quantity being rounded to a boolean determining
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* whether the value should be rounded toward infinity or toward zero.
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*
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* <p>The parameters are of type int because benchmarks on an x86-64 processor against OpenJDK
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* showed that ints were demonstrably faster than enums in switch statements.
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*
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* @param isEven Whether the digit immediately before the rounding magnitude is even.
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* @param isNegative Whether the quantity is negative.
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* @param section Whether the part of the quantity to the right of the rounding magnitude is
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* exactly halfway between two digits, whether it is in the lower part (closer to zero), or
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* whether it is in the upper part (closer to infinity). See {@link #SECTION_LOWER}, {@link
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* #SECTION_MIDPOINT}, and {@link #SECTION_UPPER}.
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* @param roundingMode The integer version of the {@link RoundingMode}, which you can get via
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* {@link RoundingMode#ordinal}.
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* @param status Error code, set to U_FORMAT_INEXACT_ERROR if the rounding mode is kRoundUnnecessary.
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* @return true if the number should be rounded toward zero; false if it should be rounded toward
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* infinity.
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*/
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inline bool
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getRoundingDirection(bool isEven, bool isNegative, Section section, RoundingMode roundingMode,
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UErrorCode &status) {
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switch (roundingMode) {
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case RoundingMode::UNUM_ROUND_UP:
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// round away from zero
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return false;
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case RoundingMode::UNUM_ROUND_DOWN:
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// round toward zero
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return true;
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case RoundingMode::UNUM_ROUND_CEILING:
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// round toward positive infinity
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return isNegative;
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case RoundingMode::UNUM_ROUND_FLOOR:
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// round toward negative infinity
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return !isNegative;
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case RoundingMode::UNUM_ROUND_HALFUP:
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switch (section) {
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case SECTION_MIDPOINT:
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return false;
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case SECTION_LOWER:
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return true;
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case SECTION_UPPER:
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return false;
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default:
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break;
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}
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break;
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case RoundingMode::UNUM_ROUND_HALFDOWN:
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switch (section) {
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case SECTION_MIDPOINT:
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return true;
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case SECTION_LOWER:
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return true;
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case SECTION_UPPER:
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return false;
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default:
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break;
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}
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break;
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case RoundingMode::UNUM_ROUND_HALFEVEN:
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switch (section) {
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case SECTION_MIDPOINT:
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return isEven;
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case SECTION_LOWER:
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return true;
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case SECTION_UPPER:
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return false;
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default:
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break;
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}
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break;
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default:
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break;
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}
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status = U_FORMAT_INEXACT_ERROR;
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return false;
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}
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/**
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* Gets whether the given rounding mode's rounding boundary is at the midpoint. The rounding
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* boundary is the point at which a number switches from being rounded down to being rounded up.
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* For example, with rounding mode HALF_EVEN, HALF_UP, or HALF_DOWN, the rounding boundary is at
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* the midpoint, and this function would return true. However, for UP, DOWN, CEILING, and FLOOR,
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* the rounding boundary is at the "edge", and this function would return false.
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*
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* @param roundingMode The integer version of the {@link RoundingMode}.
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* @return true if rounding mode is HALF_EVEN, HALF_UP, or HALF_DOWN; false otherwise.
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*/
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inline bool roundsAtMidpoint(int roundingMode) {
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switch (roundingMode) {
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case RoundingMode::UNUM_ROUND_UP:
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case RoundingMode::UNUM_ROUND_DOWN:
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case RoundingMode::UNUM_ROUND_CEILING:
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case RoundingMode::UNUM_ROUND_FLOOR:
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return false;
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default:
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return true;
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}
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}
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/**
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* Computes the number of fraction digits in a double. Used for computing maxFrac for an increment.
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* Calls into the DoubleToStringConverter library to do so.
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*/
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digits_t doubleFractionLength(double input);
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} // namespace roundingutils
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} // namespace impl
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} // namespace number
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U_NAMESPACE_END
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#endif //__NUMBER_ROUNDINGUTILS_H__
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#endif /* #if !UCONFIG_NO_FORMATTING */
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