Repo created

TMessagesProj/jni/voip/webrtc/rtc_base/numerics/math_utils.h

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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 <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_