76 lines
2.6 KiB
C++
76 lines
2.6 KiB
C++
/*
|
|
* Copyright 2005 The WebRTC Project Authors. All rights reserved.
|
|
*
|
|
* Use of this source code is governed by a BSD-style license
|
|
* that can be found in the LICENSE file in the root of the source
|
|
* tree. An additional intellectual property rights grant can be found
|
|
* in the file PATENTS. All contributing project authors may
|
|
* be found in the AUTHORS file in the root of the source tree.
|
|
*/
|
|
|
|
#ifndef API_NUMERICS_MATH_UTILS_H_
|
|
#define API_NUMERICS_MATH_UTILS_H_
|
|
|
|
#include <limits>
|
|
#include <type_traits>
|
|
|
|
#include "rtc_base/checks.h"
|
|
|
|
namespace webrtc {
|
|
namespace webrtc_impl {
|
|
// Given two numbers `x` and `y` such that x >= y, computes the difference
|
|
// x - y without causing undefined behavior due to signed overflow.
|
|
template <typename T>
|
|
typename std::make_unsigned<T>::type unsigned_difference(T x, T y) {
|
|
static_assert(
|
|
std::is_signed<T>::value,
|
|
"Function unsigned_difference is only meaningful for signed types.");
|
|
RTC_DCHECK_GE(x, y);
|
|
typedef typename std::make_unsigned<T>::type unsigned_type;
|
|
// int -> unsigned conversion repeatedly adds UINT_MAX + 1 until the number
|
|
// can be represented as an unsigned. Since we know that the actual
|
|
// difference x - y can be represented as an unsigned, it is sufficient to
|
|
// compute the difference modulo UINT_MAX + 1, i.e using unsigned arithmetic.
|
|
return static_cast<unsigned_type>(x) - static_cast<unsigned_type>(y);
|
|
}
|
|
|
|
// Provide neutral element with respect to min().
|
|
// Typically used as an initial value for running minimum.
|
|
template <typename T,
|
|
typename std::enable_if<std::numeric_limits<T>::has_infinity>::type* =
|
|
nullptr>
|
|
constexpr T infinity_or_max() {
|
|
return std::numeric_limits<T>::infinity();
|
|
}
|
|
|
|
template <typename T,
|
|
typename std::enable_if<
|
|
!std::numeric_limits<T>::has_infinity>::type* = nullptr>
|
|
constexpr T infinity_or_max() {
|
|
// Fallback to max().
|
|
return std::numeric_limits<T>::max();
|
|
}
|
|
|
|
// Provide neutral element with respect to max().
|
|
// Typically used as an initial value for running maximum.
|
|
template <typename T,
|
|
typename std::enable_if<std::numeric_limits<T>::has_infinity>::type* =
|
|
nullptr>
|
|
constexpr T minus_infinity_or_min() {
|
|
static_assert(std::is_signed<T>::value, "Unsupported. Please open a bug.");
|
|
return -std::numeric_limits<T>::infinity();
|
|
}
|
|
|
|
template <typename T,
|
|
typename std::enable_if<
|
|
!std::numeric_limits<T>::has_infinity>::type* = nullptr>
|
|
constexpr T minus_infinity_or_min() {
|
|
// Fallback to min().
|
|
return std::numeric_limits<T>::min();
|
|
}
|
|
|
|
} // namespace webrtc_impl
|
|
} // namespace webrtc
|
|
|
|
#endif // API_NUMERICS_MATH_UTILS_H_
|