integer_division.h

// Copyright 2024 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
 
#include <type_traits>
 
namespace pw {
 
template <typename T>
constexpr T IntegerDivisionRoundNearest(T dividend, T divisor) {
  static_assert(std::is_integral_v<T> && !std::is_same_v<T, bool>);
  // Integer division typically truncates towards zero, so change the direction
  // of the bias when the quotient is negative.
  if constexpr (std::is_signed_v<T>) {
    if ((dividend < 0) != (divisor < 0)) {
      return (dividend - divisor / T{2}) / divisor;
    }
  }
 
  return (dividend + divisor / T{2}) / divisor;
}
 
}  // namespace pw