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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 RTC_BASE_NUMERICS_MATHUTILS_H_
#define RTC_BASE_NUMERICS_MATHUTILS_H_
#include <math.h>
#include <type_traits>
#include "rtc_base/checks.h"
#ifndef M_PI
#define M_PI 3.14159265359f
#endif
// 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);
}
#endif // RTC_BASE_NUMERICS_MATHUTILS_H_
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