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 /* * 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 #include #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 std::make_unsigned::type unsigned_difference(T x, T y) { static_assert( std::is_signed::value, "Function unsigned_difference is only meaningful for signed types."); RTC_DCHECK_GE(x, y); typedef typename std::make_unsigned::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(x) - static_cast(y); } // Provide neutral element with respect to min(). // Typically used as an initial value for running minimum. template ::has_infinity>::type* = nullptr> constexpr T infinity_or_max() { return std::numeric_limits::infinity(); } template ::has_infinity>::type* = nullptr> constexpr T infinity_or_max() { // Fallback to max(). return std::numeric_limits::max(); } // Provide neutral element with respect to max(). // Typically used as an initial value for running maximum. template ::has_infinity>::type* = nullptr> constexpr T minus_infinity_or_min() { static_assert(std::is_signed::value, "Unsupported. Please open a bug."); return -std::numeric_limits::infinity(); } template ::has_infinity>::type* = nullptr> constexpr T minus_infinity_or_min() { // Fallback to min(). return std::numeric_limits::min(); } } // namespace webrtc_impl } // namespace webrtc #endif // API_NUMERICS_MATH_UTILS_H_