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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UTIL_INTEGER_DIVISION_H_
#define UTIL_INTEGER_DIVISION_H_
#include <type_traits>
namespace openscreen {
// Returns CEIL(num รท denom). |denom| must not equal zero. This function is
// compatible with any integer-like type, including the integer-based
// std::chrono duration types.
//
// Optimization note: See DividePositivesRoundingUp().
template <typename Integer>
constexpr auto DivideRoundingUp(Integer num, Integer denom) {
if (denom < Integer{0}) {
num *= -1;
denom *= -1;
}
if (num < Integer{0}) {
return num / denom;
}
return (num + denom - Integer{1}) / denom;
}
// Same as DivideRoundingUp(), except is more-efficient for hot code paths that
// know |num| is always greater or equal to zero, and |denom| is always greater
// than zero.
template <typename Integer>
constexpr Integer DividePositivesRoundingUp(Integer num, Integer denom) {
return DivideRoundingUp<typename std::make_unsigned<Integer>::type>(num,
denom);
}
// Divides |num| by |denom|, and rounds to the nearest integer (exactly halfway
// between integers will round to the higher integer). This function is
// compatible with any integer-like type, including the integer-based
// std::chrono duration types.
//
// Optimization note: See DividePositivesRoundingNearest().
template <typename Integer>
constexpr auto DivideRoundingNearest(Integer num, Integer denom) {
if (denom < Integer{0}) {
num *= -1;
denom *= -1;
}
if (num < Integer{0}) {
return (num - ((denom - Integer{1}) / 2)) / denom;
}
return (num + (denom / 2)) / denom;
}
// Same as DivideRoundingNearest(), except is more-efficient for hot code paths
// that know |num| is always greater or equal to zero, and |denom| is always
// greater than zero.
template <typename Integer>
constexpr Integer DividePositivesRoundingNearest(Integer num, Integer denom) {
return DivideRoundingNearest<typename std::make_unsigned<Integer>::type>(
num, denom);
}
} // namespace openscreen
#endif // UTIL_INTEGER_DIVISION_H_
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