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Diffstat (limited to 'third_party/numerics/safe_math_impl.h')
| -rw-r--r-- | third_party/numerics/safe_math_impl.h | 502 |
1 files changed, 0 insertions, 502 deletions
diff --git a/third_party/numerics/safe_math_impl.h b/third_party/numerics/safe_math_impl.h deleted file mode 100644 index 4bf59e64e0..0000000000 --- a/third_party/numerics/safe_math_impl.h +++ /dev/null @@ -1,502 +0,0 @@ -// Copyright 2014 The Chromium Authors. All rights reserved. -// Use of this source code is governed by a BSD-style license that can be -// found in the LICENSE file. - -#ifndef SAFE_MATH_IMPL_H_ -#define SAFE_MATH_IMPL_H_ - -#include <stdint.h> - -#include <cmath> -#include <cstdlib> -#include <limits> - -#include "../macros.h" -#include "../template_util.h" -#include "safe_conversions.h" - -namespace base { -namespace internal { - -// Everything from here up to the floating point operations is portable C++, -// but it may not be fast. This code could be split based on -// platform/architecture and replaced with potentially faster implementations. - -// Integer promotion templates used by the portable checked integer arithmetic. -template <size_t Size, bool IsSigned> -struct IntegerForSizeAndSign; -template <> -struct IntegerForSizeAndSign<1, true> { - typedef int8_t type; -}; -template <> -struct IntegerForSizeAndSign<1, false> { - typedef uint8_t type; -}; -template <> -struct IntegerForSizeAndSign<2, true> { - typedef int16_t type; -}; -template <> -struct IntegerForSizeAndSign<2, false> { - typedef uint16_t type; -}; -template <> -struct IntegerForSizeAndSign<4, true> { - typedef int32_t type; -}; -template <> -struct IntegerForSizeAndSign<4, false> { - typedef uint32_t type; -}; -template <> -struct IntegerForSizeAndSign<8, true> { - typedef int64_t type; -}; -template <> -struct IntegerForSizeAndSign<8, false> { - typedef uint64_t type; -}; - -// WARNING: We have no IntegerForSizeAndSign<16, *>. If we ever add one to -// support 128-bit math, then the ArithmeticPromotion template below will need -// to be updated (or more likely replaced with a decltype expression). - -template <typename Integer> -struct UnsignedIntegerForSize { - typedef typename enable_if< - std::numeric_limits<Integer>::is_integer, - typename IntegerForSizeAndSign<sizeof(Integer), false>::type>::type type; -}; - -template <typename Integer> -struct SignedIntegerForSize { - typedef typename enable_if< - std::numeric_limits<Integer>::is_integer, - typename IntegerForSizeAndSign<sizeof(Integer), true>::type>::type type; -}; - -template <typename Integer> -struct TwiceWiderInteger { - typedef typename enable_if< - std::numeric_limits<Integer>::is_integer, - typename IntegerForSizeAndSign< - sizeof(Integer) * 2, - std::numeric_limits<Integer>::is_signed>::type>::type type; -}; - -template <typename Integer> -struct PositionOfSignBit { - static const typename enable_if<std::numeric_limits<Integer>::is_integer, - size_t>::type value = 8 * sizeof(Integer) - 1; -}; - -// Helper templates for integer manipulations. - -template <typename T> -bool HasSignBit(T x) { - // Cast to unsigned since right shift on signed is undefined. - return !!(static_cast<typename UnsignedIntegerForSize<T>::type>(x) >> - PositionOfSignBit<T>::value); -} - -// This wrapper undoes the standard integer promotions. -template <typename T> -T BinaryComplement(T x) { - return ~x; -} - -// Here are the actual portable checked integer math implementations. -// TODO(jschuh): Break this code out from the enable_if pattern and find a clean -// way to coalesce things into the CheckedNumericState specializations below. - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_integer, T>::type -CheckedAdd(T x, T y, RangeConstraint* validity) { - // Since the value of x+y is undefined if we have a signed type, we compute - // it using the unsigned type of the same size. - typedef typename UnsignedIntegerForSize<T>::type UnsignedDst; - UnsignedDst ux = static_cast<UnsignedDst>(x); - UnsignedDst uy = static_cast<UnsignedDst>(y); - UnsignedDst uresult = ux + uy; - // Addition is valid if the sign of (x + y) is equal to either that of x or - // that of y. - if (std::numeric_limits<T>::is_signed) { - if (HasSignBit(BinaryComplement((uresult ^ ux) & (uresult ^ uy)))) - *validity = RANGE_VALID; - else // Direction of wrap is inverse of result sign. - *validity = HasSignBit(uresult) ? RANGE_OVERFLOW : RANGE_UNDERFLOW; - - } else { // Unsigned is either valid or overflow. - *validity = BinaryComplement(x) >= y ? RANGE_VALID : RANGE_OVERFLOW; - } - return static_cast<T>(uresult); -} - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_integer, T>::type -CheckedSub(T x, T y, RangeConstraint* validity) { - // Since the value of x+y is undefined if we have a signed type, we compute - // it using the unsigned type of the same size. - typedef typename UnsignedIntegerForSize<T>::type UnsignedDst; - UnsignedDst ux = static_cast<UnsignedDst>(x); - UnsignedDst uy = static_cast<UnsignedDst>(y); - UnsignedDst uresult = ux - uy; - // Subtraction is valid if either x and y have same sign, or (x-y) and x have - // the same sign. - if (std::numeric_limits<T>::is_signed) { - if (HasSignBit(BinaryComplement((uresult ^ ux) & (ux ^ uy)))) - *validity = RANGE_VALID; - else // Direction of wrap is inverse of result sign. - *validity = HasSignBit(uresult) ? RANGE_OVERFLOW : RANGE_UNDERFLOW; - - } else { // Unsigned is either valid or underflow. - *validity = x >= y ? RANGE_VALID : RANGE_UNDERFLOW; - } - return static_cast<T>(uresult); -} - -// Integer multiplication is a bit complicated. In the fast case we just -// we just promote to a twice wider type, and range check the result. In the -// slow case we need to manually check that the result won't be truncated by -// checking with division against the appropriate bound. -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer && sizeof(T) * 2 <= sizeof(uintmax_t), - T>::type -CheckedMul(T x, T y, RangeConstraint* validity) { - typedef typename TwiceWiderInteger<T>::type IntermediateType; - IntermediateType tmp = - static_cast<IntermediateType>(x) * static_cast<IntermediateType>(y); - *validity = DstRangeRelationToSrcRange<T>(tmp); - return static_cast<T>(tmp); -} - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_integer&& std::numeric_limits< - T>::is_signed&&(sizeof(T) * 2 > sizeof(uintmax_t)), - T>::type -CheckedMul(T x, T y, RangeConstraint* validity) { - // if either side is zero then the result will be zero. - if (!(x || y)) { - return RANGE_VALID; - - } else if (x > 0) { - if (y > 0) - *validity = - x <= std::numeric_limits<T>::max() / y ? RANGE_VALID : RANGE_OVERFLOW; - else - *validity = y >= std::numeric_limits<T>::min() / x ? RANGE_VALID - : RANGE_UNDERFLOW; - - } else { - if (y > 0) - *validity = x >= std::numeric_limits<T>::min() / y ? RANGE_VALID - : RANGE_UNDERFLOW; - else - *validity = - y >= std::numeric_limits<T>::max() / x ? RANGE_VALID : RANGE_OVERFLOW; - } - - return x * y; -} - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_integer && - !std::numeric_limits<T>::is_signed && - (sizeof(T) * 2 > sizeof(uintmax_t)), - T>::type -CheckedMul(T x, T y, RangeConstraint* validity) { - *validity = (y == 0 || x <= std::numeric_limits<T>::max() / y) - ? RANGE_VALID - : RANGE_OVERFLOW; - return x * y; -} - -// Division just requires a check for an invalid negation on signed min/-1. -template <typename T> -T CheckedDiv( - T x, - T y, - RangeConstraint* validity, - typename enable_if<std::numeric_limits<T>::is_integer, int>::type = 0) { - if (std::numeric_limits<T>::is_signed && x == std::numeric_limits<T>::min() && - y == static_cast<T>(-1)) { - *validity = RANGE_OVERFLOW; - return std::numeric_limits<T>::min(); - } - - *validity = RANGE_VALID; - return x / y; -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer&& std::numeric_limits<T>::is_signed, - T>::type -CheckedMod(T x, T y, RangeConstraint* validity) { - *validity = y > 0 ? RANGE_VALID : RANGE_INVALID; - return x % y; -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer && !std::numeric_limits<T>::is_signed, - T>::type -CheckedMod(T x, T y, RangeConstraint* validity) { - *validity = RANGE_VALID; - return x % y; -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer&& std::numeric_limits<T>::is_signed, - T>::type -CheckedNeg(T value, RangeConstraint* validity) { - *validity = - value != std::numeric_limits<T>::min() ? RANGE_VALID : RANGE_OVERFLOW; - // The negation of signed min is min, so catch that one. - return -value; -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer && !std::numeric_limits<T>::is_signed, - T>::type -CheckedNeg(T value, RangeConstraint* validity) { - // The only legal unsigned negation is zero. - *validity = value ? RANGE_UNDERFLOW : RANGE_VALID; - return static_cast<T>( - -static_cast<typename SignedIntegerForSize<T>::type>(value)); -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer&& std::numeric_limits<T>::is_signed, - T>::type -CheckedAbs(T value, RangeConstraint* validity) { - *validity = - value != std::numeric_limits<T>::min() ? RANGE_VALID : RANGE_OVERFLOW; - return std::abs(value); -} - -template <typename T> -typename enable_if< - std::numeric_limits<T>::is_integer && !std::numeric_limits<T>::is_signed, - T>::type -CheckedAbs(T value, RangeConstraint* validity) { - // Absolute value of a positive is just its identiy. - *validity = RANGE_VALID; - return value; -} - -// These are the floating point stubs that the compiler needs to see. Only the -// negation operation is ever called. -#define BASE_FLOAT_ARITHMETIC_STUBS(NAME) \ - template <typename T> \ - typename enable_if<std::numeric_limits<T>::is_iec559, T>::type \ - Checked##NAME(T, T, RangeConstraint*) { \ - NOTREACHED(); \ - return 0; \ - } - -BASE_FLOAT_ARITHMETIC_STUBS(Add) -BASE_FLOAT_ARITHMETIC_STUBS(Sub) -BASE_FLOAT_ARITHMETIC_STUBS(Mul) -BASE_FLOAT_ARITHMETIC_STUBS(Div) -BASE_FLOAT_ARITHMETIC_STUBS(Mod) - -#undef BASE_FLOAT_ARITHMETIC_STUBS - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_iec559, T>::type CheckedNeg( - T value, - RangeConstraint*) { - return -value; -} - -template <typename T> -typename enable_if<std::numeric_limits<T>::is_iec559, T>::type CheckedAbs( - T value, - RangeConstraint*) { - return std::abs(value); -} - -// Floats carry around their validity state with them, but integers do not. So, -// we wrap the underlying value in a specialization in order to hide that detail -// and expose an interface via accessors. -enum NumericRepresentation { - NUMERIC_INTEGER, - NUMERIC_FLOATING, - NUMERIC_UNKNOWN -}; - -template <typename NumericType> -struct GetNumericRepresentation { - static const NumericRepresentation value = - std::numeric_limits<NumericType>::is_integer - ? NUMERIC_INTEGER - : (std::numeric_limits<NumericType>::is_iec559 ? NUMERIC_FLOATING - : NUMERIC_UNKNOWN); -}; - -template <typename T, NumericRepresentation type = - GetNumericRepresentation<T>::value> -class CheckedNumericState {}; - -// Integrals require quite a bit of additional housekeeping to manage state. -template <typename T> -class CheckedNumericState<T, NUMERIC_INTEGER> { - private: - T value_; - RangeConstraint validity_; - - public: - template <typename Src, NumericRepresentation type> - friend class CheckedNumericState; - - CheckedNumericState() : value_(0), validity_(RANGE_VALID) {} - - template <typename Src> - CheckedNumericState(Src value, RangeConstraint validity) - : value_(value), - validity_(GetRangeConstraint(validity | - DstRangeRelationToSrcRange<T>(value))) { - COMPILE_ASSERT(std::numeric_limits<Src>::is_specialized, - argument_must_be_numeric); - } - - // Copy constructor. - template <typename Src> - CheckedNumericState(const CheckedNumericState<Src>& rhs) - : value_(static_cast<T>(rhs.value())), - validity_(GetRangeConstraint( - rhs.validity() | DstRangeRelationToSrcRange<T>(rhs.value()))) {} - - template <typename Src> - explicit CheckedNumericState( - Src value, - typename enable_if<std::numeric_limits<Src>::is_specialized, int>::type = - 0) - : value_(static_cast<T>(value)), - validity_(DstRangeRelationToSrcRange<T>(value)) {} - - RangeConstraint validity() const { return validity_; } - T value() const { return value_; } -}; - -// Floating points maintain their own validity, but need translation wrappers. -template <typename T> -class CheckedNumericState<T, NUMERIC_FLOATING> { - private: - T value_; - - public: - template <typename Src, NumericRepresentation type> - friend class CheckedNumericState; - - CheckedNumericState() : value_(0.0) {} - - template <typename Src> - CheckedNumericState( - Src value, - RangeConstraint validity, - typename enable_if<std::numeric_limits<Src>::is_integer, int>::type = 0) { - switch (DstRangeRelationToSrcRange<T>(value)) { - case RANGE_VALID: - value_ = static_cast<T>(value); - break; - - case RANGE_UNDERFLOW: - value_ = -std::numeric_limits<T>::infinity(); - break; - - case RANGE_OVERFLOW: - value_ = std::numeric_limits<T>::infinity(); - break; - - case RANGE_INVALID: - value_ = std::numeric_limits<T>::quiet_NaN(); - break; - - default: - NOTREACHED(); - } - } - - template <typename Src> - explicit CheckedNumericState( - Src value, - typename enable_if<std::numeric_limits<Src>::is_specialized, int>::type = - 0) - : value_(static_cast<T>(value)) {} - - // Copy constructor. - template <typename Src> - CheckedNumericState(const CheckedNumericState<Src>& rhs) - : value_(static_cast<T>(rhs.value())) {} - - RangeConstraint validity() const { - return GetRangeConstraint(value_ <= std::numeric_limits<T>::max(), - value_ >= -std::numeric_limits<T>::max()); - } - T value() const { return value_; } -}; - -// For integers less than 128-bit and floats 32-bit or larger, we can distil -// C/C++ arithmetic promotions down to two simple rules: -// 1. The type with the larger maximum exponent always takes precedence. -// 2. The resulting type must be promoted to at least an int. -// The following template specializations implement that promotion logic. -enum ArithmeticPromotionCategory { - LEFT_PROMOTION, - RIGHT_PROMOTION, - DEFAULT_PROMOTION -}; - -template <typename Lhs, - typename Rhs = Lhs, - ArithmeticPromotionCategory Promotion = - (MaxExponent<Lhs>::value > MaxExponent<Rhs>::value) - ? (MaxExponent<Lhs>::value > MaxExponent<int>::value - ? LEFT_PROMOTION - : DEFAULT_PROMOTION) - : (MaxExponent<Rhs>::value > MaxExponent<int>::value - ? RIGHT_PROMOTION - : DEFAULT_PROMOTION) > -struct ArithmeticPromotion; - -template <typename Lhs, typename Rhs> -struct ArithmeticPromotion<Lhs, Rhs, LEFT_PROMOTION> { - typedef Lhs type; -}; - -template <typename Lhs, typename Rhs> -struct ArithmeticPromotion<Lhs, Rhs, RIGHT_PROMOTION> { - typedef Rhs type; -}; - -template <typename Lhs, typename Rhs> -struct ArithmeticPromotion<Lhs, Rhs, DEFAULT_PROMOTION> { - typedef int type; -}; - -// We can statically check if operations on the provided types can wrap, so we -// can skip the checked operations if they're not needed. So, for an integer we -// care if the destination type preserves the sign and is twice the width of -// the source. -template <typename T, typename Lhs, typename Rhs> -struct IsIntegerArithmeticSafe { - static const bool value = !std::numeric_limits<T>::is_iec559 && - StaticDstRangeRelationToSrcRange<T, Lhs>::value == - NUMERIC_RANGE_CONTAINED && - sizeof(T) >= (2 * sizeof(Lhs)) && - StaticDstRangeRelationToSrcRange<T, Rhs>::value != - NUMERIC_RANGE_CONTAINED && - sizeof(T) >= (2 * sizeof(Rhs)); -}; - -} // namespace internal -} // namespace base - -#endif // SAFE_MATH_IMPL_H_ |