Revert of Safe numeric library: base/numerics (copied from Chromium)

webrtc/base/numerics/safe_conversions.h

-/*
- *  Copyright (c) 2016 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.
- *
- */
-
-// Borrowed from Chromium's src/base/numerics/safe_conversions.h.
-// - Modified to work in WebRTC (paths, namespace, use of webrtc/base).
-//   Based on 'chromium_revision': 'ee311243eae6aef9c907543663754ff38f1f4f40'.
-
-#ifndef WEBRTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
-#define WEBRTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
-
-#include <stddef.h>
-
-#include <limits>
-#include <type_traits>
-
-#include "webrtc/base/numerics/safe_conversions_impl.h"
-
-namespace rtc {
-
-// Convenience function that returns true if the supplied value is in range
-// for the destination type.
-template <typename Dst, typename Src>
-inline bool IsValueInRangeForNumericType(Src value) {
-  return internal::DstRangeRelationToSrcRange<Dst>(value) ==
-         internal::RANGE_VALID;
-}
-
-// Convenience function for determining if a numeric value is negative without
-// throwing compiler warnings on: unsigned(value) < 0.
-template <typename T>
-typename std::enable_if<std::numeric_limits<T>::is_signed, bool>::type
-IsValueNegative(T value) {
-  static_assert(std::numeric_limits<T>::is_specialized,
-                "Argument must be numeric.");
-  return value < 0;
-}
-
-template <typename T>
-typename std::enable_if<!std::numeric_limits<T>::is_signed, bool>::type
-    IsValueNegative(T) {
-  static_assert(std::numeric_limits<T>::is_specialized,
-                "Argument must be numeric.");
-  return false;
-}
-
-// checked_cast<> is analogous to static_cast<> for numeric types,
-// except that it CHECKs that the specified numeric conversion will not
-// overflow or underflow. NaN source will always trigger a CHECK.
-template <typename Dst, typename Src>
-inline Dst checked_cast(Src value) {
-  RTC_CHECK(IsValueInRangeForNumericType<Dst>(value));
-  return static_cast<Dst>(value);
-}
-
-// HandleNaN will cause this class to RTC_CHECK(false).
-struct SaturatedCastNaNBehaviorCheck {
-  template <typename T>
-  static T HandleNaN() {
-    RTC_CHECK(false);
-    return T();
-  }
-};
-
-// HandleNaN will return 0 in this case.
-struct SaturatedCastNaNBehaviorReturnZero {
-  template <typename T>
-  static T HandleNaN() {
-    return T();
-  }
-};
-
-// saturated_cast<> is analogous to static_cast<> for numeric types, except
-// that the specified numeric conversion will saturate rather than overflow or
-// underflow. NaN assignment to an integral will defer the behavior to a
-// specified class. By default, it will return 0.
-template <typename Dst,
-          class NaNHandler = SaturatedCastNaNBehaviorReturnZero,
-          typename Src>
-inline Dst saturated_cast(Src value) {
-  // Optimization for floating point values, which already saturate.
-  if (std::numeric_limits<Dst>::is_iec559)
-    return static_cast<Dst>(value);
-
-  switch (internal::DstRangeRelationToSrcRange<Dst>(value)) {
-    case internal::RANGE_VALID:
-      return static_cast<Dst>(value);
-
-    case internal::RANGE_UNDERFLOW:
-      return std::numeric_limits<Dst>::min();
-
-    case internal::RANGE_OVERFLOW:
-      return std::numeric_limits<Dst>::max();
-
-    // Should fail only on attempting to assign NaN to a saturated integer.
-    case internal::RANGE_INVALID:
-      return NaNHandler::template HandleNaN<Dst>();
-  }
-
-  RTC_NOTREACHED();
-  return static_cast<Dst>(value);
-}
-
-// strict_cast<> is analogous to static_cast<> for numeric types, except that
-// it will cause a compile failure if the destination type is not large enough
-// to contain any value in the source type. It performs no runtime checking.
-template <typename Dst, typename Src>
-inline Dst strict_cast(Src value) {
-  static_assert(std::numeric_limits<Src>::is_specialized,
-                "Argument must be numeric.");
-  static_assert(std::numeric_limits<Dst>::is_specialized,
-                "Result must be numeric.");
-  static_assert((internal::StaticDstRangeRelationToSrcRange<Dst, Src>::value ==
-                 internal::NUMERIC_RANGE_CONTAINED),
-                "The numeric conversion is out of range for this type. You "
-                "should probably use one of the following conversion "
-                "mechanisms on the value you want to pass:\n"
-                "- rtc::checked_cast\n"
-                "- rtc::saturated_cast\n"
-                "- rtc::CheckedNumeric");
-
-  return static_cast<Dst>(value);
-}
-
-// StrictNumeric implements compile time range checking between numeric types by
-// wrapping assignment operations in a strict_cast. This class is intended to be
-// used for function arguments and return types, to ensure the destination type
-// can always contain the source type. This is essentially the same as enforcing
-// -Wconversion in gcc and C4302 warnings on MSVC, but it can be applied
-// incrementally at API boundaries, making it easier to convert code so that it
-// compiles cleanly with truncation warnings enabled.
-// This template should introduce no runtime overhead, but it also provides no
-// runtime checking of any of the associated mathematical operations. Use
-// CheckedNumeric for runtime range checks of tha actual value being assigned.
-template <typename T>
-class StrictNumeric {
- public:
-  typedef T type;
-
-  StrictNumeric() : value_(0) {}
-
-  // Copy constructor.
-  template <typename Src>
-  StrictNumeric(const StrictNumeric<Src>& rhs)
-      : value_(strict_cast<T>(rhs.value_)) {}
-
-  // This is not an explicit constructor because we implicitly upgrade regular
-  // numerics to StrictNumerics to make them easier to use.
-  template <typename Src>
-  StrictNumeric(Src value)
-      : value_(strict_cast<T>(value)) {}
-
-  // The numeric cast operator basically handles all the magic.
-  template <typename Dst>
-  operator Dst() const {
-    return strict_cast<Dst>(value_);
-  }
-
- private:
-  T value_;
-};
-
-// Explicitly make a shorter size_t typedef for convenience.
-typedef StrictNumeric<size_t> SizeT;
-
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_