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