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

webrtc/base/numerics/safe_math.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_math.h.
-// - Modified to work in WebRTC (paths, namespace, use of webrtc/base).
-//   Based on 'chromium_revision': 'ee311243eae6aef9c907543663754ff38f1f4f40'.
-
-#ifndef WEBRTC_BASE_NUMERICS_SAFE_MATH_H_
-#define WEBRTC_BASE_NUMERICS_SAFE_MATH_H_
-
-#include <stddef.h>
-#include <type_traits>
-
-#include "webrtc/base/checks.h"
-#include "webrtc/base/numerics/safe_math_impl.h"
-
-namespace rtc {
-
-namespace internal {
-
-// CheckedNumeric implements all the logic and operators for detecting integer
-// boundary conditions such as overflow, underflow, and invalid conversions.
-// The CheckedNumeric type implicitly converts from floating point and integer
-// data types, and contains overloads for basic arithmetic operations (i.e.: +,
-// -, *, /, %).
-//
-// The following methods convert from CheckedNumeric to standard numeric values:
-// IsValid() - Returns true if the underlying numeric value is valid (i.e. has
-//             has not wrapped and is not the result of an invalid conversion).
-// ValueOrDie() - Returns the underlying value. If the state is not valid this
-//                call will crash on a RTC_CHECK.
-// ValueOrDefault() - Returns the current value, or the supplied default if the
-//                    state is not valid.
-// ValueFloating() - Returns the underlying floating point value (valid only
-//                   only for floating point CheckedNumeric types).
-//
-// Bitwise operations are explicitly not supported, because correct
-// handling of some cases (e.g. sign manipulation) is ambiguous. Comparison
-// operations are explicitly not supported because they could result in a crash
-// on a RTC_CHECK condition. You should use patterns like the following for
-// these operations:
-// Bitwise operation:
-//     CheckedNumeric<int> checked_int = untrusted_input_value;
-//     int x = checked_int.ValueOrDefault(0) | kFlagValues;
-// Comparison:
-//   CheckedNumeric<size_t> checked_size = untrusted_input_value;
-//   checked_size += HEADER LENGTH;
-//   if (checked_size.IsValid() && checked_size.ValueOrDie() < buffer_size)
-//     Do stuff...
-template <typename T>
-class CheckedNumeric {
- public:
-  typedef T type;
-
-  CheckedNumeric() {}
-
-  // Copy constructor.
-  template <typename Src>
-  CheckedNumeric(const CheckedNumeric<Src>& rhs)
-      : state_(rhs.ValueUnsafe(), rhs.validity()) {}
-
-  template <typename Src>
-  CheckedNumeric(Src value, RangeConstraint validity)
-      : state_(value, validity) {}
-
-  // This is not an explicit constructor because we implicitly upgrade regular
-  // numerics to CheckedNumerics to make them easier to use.
-  template <typename Src>
-  CheckedNumeric(Src value)
-      : state_(value) {
-    static_assert(std::numeric_limits<Src>::is_specialized,
-                  "Argument must be numeric.");
-  }
-
-  // This is not an explicit constructor because we want a seamless conversion
-  // from StrictNumeric types.
-  template <typename Src>
-  CheckedNumeric(StrictNumeric<Src> value)
-      : state_(static_cast<Src>(value)) {
-  }
-
-  // IsValid() is the public API to test if a CheckedNumeric is currently valid.
-  bool IsValid() const { return validity() == RANGE_VALID; }
-
-  // ValueOrDie() The primary accessor for the underlying value. If the current
-  // state is not valid it will RTC_CHECK and crash.
-  T ValueOrDie() const {
-    RTC_CHECK(IsValid());
-    return state_.value();
-  }
-
-  // ValueOrDefault(T default_value) A convenience method that returns the
-  // current value if the state is valid, and the supplied default_value for
-  // any other state.
-  T ValueOrDefault(T default_value) const {
-    return IsValid() ? state_.value() : default_value;
-  }
-
-  // ValueFloating() - Since floating point values include their validity state,
-  // we provide an easy method for extracting them directly, without a risk of
-  // crashing on a RTC_CHECK.
-  T ValueFloating() const {
-    static_assert(std::numeric_limits<T>::is_iec559, "Argument must be float.");
-    return CheckedNumeric<T>::cast(*this).ValueUnsafe();
-  }
-
-  // validity() - DO NOT USE THIS IN EXTERNAL CODE - It is public right now for
-  // tests and to avoid a big matrix of friend operator overloads. But the
-  // values it returns are likely to change in the future.
-  // Returns: current validity state (i.e. valid, overflow, underflow, nan).
-  // TODO(jschuh): crbug.com/332611 Figure out and implement semantics for
-  // saturation/wrapping so we can expose this state consistently and implement
-  // saturated arithmetic.
-  RangeConstraint validity() const { return state_.validity(); }
-
-  // ValueUnsafe() - DO NOT USE THIS IN EXTERNAL CODE - It is public right now
-  // for tests and to avoid a big matrix of friend operator overloads. But the
-  // values it returns are likely to change in the future.
-  // Returns: the raw numeric value, regardless of the current state.
-  // TODO(jschuh): crbug.com/332611 Figure out and implement semantics for
-  // saturation/wrapping so we can expose this state consistently and implement
-  // saturated arithmetic.
-  T ValueUnsafe() const { return state_.value(); }
-
-  // Prototypes for the supported arithmetic operator overloads.
-  template <typename Src> CheckedNumeric& operator+=(Src rhs);
-  template <typename Src> CheckedNumeric& operator-=(Src rhs);
-  template <typename Src> CheckedNumeric& operator*=(Src rhs);
-  template <typename Src> CheckedNumeric& operator/=(Src rhs);
-  template <typename Src> CheckedNumeric& operator%=(Src rhs);
-
-  CheckedNumeric operator-() const {
-    RangeConstraint validity;
-    T value = CheckedNeg(state_.value(), &validity);
-    // Negation is always valid for floating point.
-    if (std::numeric_limits<T>::is_iec559)
-      return CheckedNumeric<T>(value);
-
-    validity = GetRangeConstraint(state_.validity() | validity);
-    return CheckedNumeric<T>(value, validity);
-  }
-
-  CheckedNumeric Abs() const {
-    RangeConstraint validity;
-    T value = CheckedAbs(state_.value(), &validity);
-    // Absolute value is always valid for floating point.
-    if (std::numeric_limits<T>::is_iec559)
-      return CheckedNumeric<T>(value);
-
-    validity = GetRangeConstraint(state_.validity() | validity);
-    return CheckedNumeric<T>(value, validity);
-  }
-
-  // This function is available only for integral types. It returns an unsigned
-  // integer of the same width as the source type, containing the absolute value
-  // of the source, and properly handling signed min.
-  CheckedNumeric<typename UnsignedOrFloatForSize<T>::type> UnsignedAbs() const {
-    return CheckedNumeric<typename UnsignedOrFloatForSize<T>::type>(
-        CheckedUnsignedAbs(state_.value()), state_.validity());
-  }
-
-  CheckedNumeric& operator++() {
-    *this += 1;
-    return *this;
-  }
-
-  CheckedNumeric operator++(int) {
-    CheckedNumeric value = *this;
-    *this += 1;
-    return value;
-  }
-
-  CheckedNumeric& operator--() {
-    *this -= 1;
-    return *this;
-  }
-
-  CheckedNumeric operator--(int) {
-    CheckedNumeric value = *this;
-    *this -= 1;
-    return value;
-  }
-
-  // These static methods behave like a convenience cast operator targeting
-  // the desired CheckedNumeric type. As an optimization, a reference is
-  // returned when Src is the same type as T.
-  template <typename Src>
-  static CheckedNumeric<T> cast(
-      Src u,
-      typename std::enable_if<std::numeric_limits<Src>::is_specialized,
-                              int>::type = 0) {
-    return u;
-  }
-
-  template <typename Src>
-  static CheckedNumeric<T> cast(
-      const CheckedNumeric<Src>& u,
-      typename std::enable_if<!std::is_same<Src, T>::value, int>::type = 0) {
-    return u;
-  }
-
-  static const CheckedNumeric<T>& cast(const CheckedNumeric<T>& u) { return u; }
-
- private:
-  template <typename NumericType>
-  struct UnderlyingType {
-    using type = NumericType;
-  };
-
-  template <typename NumericType>
-  struct UnderlyingType<CheckedNumeric<NumericType>> {
-    using type = NumericType;
-  };
-
-  CheckedNumericState<T> state_;
-};
-
-// This is the boilerplate for the standard arithmetic operator overloads. A
-// macro isn't the prettiest solution, but it beats rewriting these five times.
-// Some details worth noting are:
-//  * We apply the standard arithmetic promotions.
-//  * We skip range checks for floating points.
-//  * We skip range checks for destination integers with sufficient range.
-// TODO(jschuh): extract these out into templates.
-#define BASE_NUMERIC_ARITHMETIC_OPERATORS(NAME, OP, COMPOUND_OP)              \
-  /* Binary arithmetic operator for CheckedNumerics of the same type. */      \
-  template <typename T>                                                       \
-  CheckedNumeric<typename ArithmeticPromotion<T>::type> operator OP(          \
-      const CheckedNumeric<T>& lhs, const CheckedNumeric<T>& rhs) {           \
-    typedef typename ArithmeticPromotion<T>::type Promotion;                  \
-    /* Floating point always takes the fast path */                           \
-    if (std::numeric_limits<T>::is_iec559)                                    \
-      return CheckedNumeric<T>(lhs.ValueUnsafe() OP rhs.ValueUnsafe());       \
-    if (IsIntegerArithmeticSafe<Promotion, T, T>::value)                      \
-      return CheckedNumeric<Promotion>(                                       \
-          lhs.ValueUnsafe() OP rhs.ValueUnsafe(),                             \
-          GetRangeConstraint(rhs.validity() | lhs.validity()));               \
-    RangeConstraint validity = RANGE_VALID;                                   \
-    T result = static_cast<T>(Checked##NAME(                                  \
-        static_cast<Promotion>(lhs.ValueUnsafe()),                            \
-        static_cast<Promotion>(rhs.ValueUnsafe()),                            \
-        &validity));                                                          \
-    return CheckedNumeric<Promotion>(                                         \
-        result,                                                               \
-        GetRangeConstraint(validity | lhs.validity() | rhs.validity()));      \
-  }                                                                           \
-  /* Assignment arithmetic operator implementation from CheckedNumeric. */    \
-  template <typename T>                                                       \
-  template <typename Src>                                                     \
-  CheckedNumeric<T>& CheckedNumeric<T>::operator COMPOUND_OP(Src rhs) {       \
-    *this = CheckedNumeric<T>::cast(*this)                                    \
-        OP CheckedNumeric<typename UnderlyingType<Src>::type>::cast(rhs);     \
-    return *this;                                                             \
-  }                                                                           \
-  /* Binary arithmetic operator for CheckedNumeric of different type. */      \
-  template <typename T, typename Src>                                         \
-  CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator OP(     \
-      const CheckedNumeric<Src>& lhs, const CheckedNumeric<T>& rhs) {         \
-    typedef typename ArithmeticPromotion<T, Src>::type Promotion;             \
-    if (IsIntegerArithmeticSafe<Promotion, T, Src>::value)                    \
-      return CheckedNumeric<Promotion>(                                       \
-          lhs.ValueUnsafe() OP rhs.ValueUnsafe(),                             \
-          GetRangeConstraint(rhs.validity() | lhs.validity()));               \
-    return CheckedNumeric<Promotion>::cast(lhs)                               \
-        OP CheckedNumeric<Promotion>::cast(rhs);                              \
-  }                                                                           \
-  /* Binary arithmetic operator for left CheckedNumeric and right numeric. */ \
-  template <typename T, typename Src>                                         \
-  CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator OP(     \
-      const CheckedNumeric<T>& lhs, Src rhs) {                                \
-    typedef typename ArithmeticPromotion<T, Src>::type Promotion;             \
-    if (IsIntegerArithmeticSafe<Promotion, T, Src>::value)                    \
-      return CheckedNumeric<Promotion>(lhs.ValueUnsafe() OP rhs,              \
-                                       lhs.validity());                       \
-    return CheckedNumeric<Promotion>::cast(lhs)                               \
-        OP CheckedNumeric<Promotion>::cast(rhs);                              \
-  }                                                                           \
-  /* Binary arithmetic operator for right numeric and left CheckedNumeric. */ \
-  template <typename T, typename Src>                                         \
-  CheckedNumeric<typename ArithmeticPromotion<T, Src>::type> operator OP(     \
-      Src lhs, const CheckedNumeric<T>& rhs) {                                \
-    typedef typename ArithmeticPromotion<T, Src>::type Promotion;             \
-    if (IsIntegerArithmeticSafe<Promotion, T, Src>::value)                    \
-      return CheckedNumeric<Promotion>(lhs OP rhs.ValueUnsafe(),              \
-                                       rhs.validity());                       \
-    return CheckedNumeric<Promotion>::cast(lhs)                               \
-        OP CheckedNumeric<Promotion>::cast(rhs);                              \
-  }
-
-BASE_NUMERIC_ARITHMETIC_OPERATORS(Add, +, += )
-BASE_NUMERIC_ARITHMETIC_OPERATORS(Sub, -, -= )
-BASE_NUMERIC_ARITHMETIC_OPERATORS(Mul, *, *= )
-BASE_NUMERIC_ARITHMETIC_OPERATORS(Div, /, /= )
-BASE_NUMERIC_ARITHMETIC_OPERATORS(Mod, %, %= )
-
-#undef BASE_NUMERIC_ARITHMETIC_OPERATORS
-
-}  // namespace internal
-
-using internal::CheckedNumeric;
-
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_NUMERICS_SAFE_MATH_H_