| /* |

| * 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 WEBRTC_BASE_MATHUTILS_H_ |

| #define WEBRTC_BASE_MATHUTILS_H_ |

| |

| #include <math.h> |

| #include <type_traits> |

| |

| #include "webrtc/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 // WEBRTC_BASE_MATHUTILS_H_ |