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Diffstat (limited to 'src/3rdparty/angle/src/common/third_party/base/anglebase/numerics/safe_conversions_impl.h')
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1 files changed, 274 insertions, 0 deletions
diff --git a/src/3rdparty/angle/src/common/third_party/base/anglebase/numerics/safe_conversions_impl.h b/src/3rdparty/angle/src/common/third_party/base/anglebase/numerics/safe_conversions_impl.h new file mode 100644 index 0000000000..10ed6c7a7f --- /dev/null +++ b/src/3rdparty/angle/src/common/third_party/base/anglebase/numerics/safe_conversions_impl.h @@ -0,0 +1,274 @@ +// 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 ANGLEBASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ +#define ANGLEBASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ + +#include <limits.h> +#include <stdint.h> + +#include <climits> +#include <limits> + +namespace angle +{ + +namespace base +{ +namespace internal +{ + +// The std library doesn't provide a binary max_exponent for integers, however +// we can compute one by adding one to the number of non-sign bits. This allows +// for accurate range comparisons between floating point and integer types. +template <typename NumericType> +struct MaxExponent +{ + static_assert(std::is_arithmetic<NumericType>::value, "Argument must be numeric."); + static const int value = + std::numeric_limits<NumericType>::is_iec559 + ? std::numeric_limits<NumericType>::max_exponent + : (sizeof(NumericType) * CHAR_BIT + 1 - std::numeric_limits<NumericType>::is_signed); +}; + +enum IntegerRepresentation +{ + INTEGER_REPRESENTATION_UNSIGNED, + INTEGER_REPRESENTATION_SIGNED +}; + +// A range for a given nunmeric Src type is contained for a given numeric Dst +// type if both numeric_limits<Src>::max() <= numeric_limits<Dst>::max() and +// numeric_limits<Src>::min() >= numeric_limits<Dst>::min() are true. +// We implement this as template specializations rather than simple static +// comparisons to ensure type correctness in our comparisons. +enum NumericRangeRepresentation +{ + NUMERIC_RANGE_NOT_CONTAINED, + NUMERIC_RANGE_CONTAINED +}; + +// Helper templates to statically determine if our destination type can contain +// maximum and minimum values represented by the source type. + +template <typename Dst, + typename Src, + IntegerRepresentation DstSign = std::numeric_limits<Dst>::is_signed + ? INTEGER_REPRESENTATION_SIGNED + : INTEGER_REPRESENTATION_UNSIGNED, + IntegerRepresentation SrcSign = std::numeric_limits<Src>::is_signed + ? INTEGER_REPRESENTATION_SIGNED + : INTEGER_REPRESENTATION_UNSIGNED> +struct StaticDstRangeRelationToSrcRange; + +// Same sign: Dst is guaranteed to contain Src only if its range is equal or +// larger. +template <typename Dst, typename Src, IntegerRepresentation Sign> +struct StaticDstRangeRelationToSrcRange<Dst, Src, Sign, Sign> +{ + static const NumericRangeRepresentation value = + MaxExponent<Dst>::value >= MaxExponent<Src>::value ? NUMERIC_RANGE_CONTAINED + : NUMERIC_RANGE_NOT_CONTAINED; +}; + +// Unsigned to signed: Dst is guaranteed to contain source only if its range is +// larger. +template <typename Dst, typename Src> +struct StaticDstRangeRelationToSrcRange<Dst, + Src, + INTEGER_REPRESENTATION_SIGNED, + INTEGER_REPRESENTATION_UNSIGNED> +{ + static const NumericRangeRepresentation value = + MaxExponent<Dst>::value > MaxExponent<Src>::value ? NUMERIC_RANGE_CONTAINED + : NUMERIC_RANGE_NOT_CONTAINED; +}; + +// Signed to unsigned: Dst cannot be statically determined to contain Src. +template <typename Dst, typename Src> +struct StaticDstRangeRelationToSrcRange<Dst, + Src, + INTEGER_REPRESENTATION_UNSIGNED, + INTEGER_REPRESENTATION_SIGNED> +{ + static const NumericRangeRepresentation value = NUMERIC_RANGE_NOT_CONTAINED; +}; + +enum RangeConstraint : unsigned char +{ + RANGE_VALID = 0x0, // Value can be represented by the destination type. + RANGE_UNDERFLOW = 0x1, // Value would overflow. + RANGE_OVERFLOW = 0x2, // Value would underflow. + RANGE_INVALID = RANGE_UNDERFLOW | RANGE_OVERFLOW // Invalid (i.e. NaN). +}; + +// Helper function for coercing an int back to a RangeContraint. +constexpr RangeConstraint GetRangeConstraint(int integer_range_constraint) +{ + // TODO(jschuh): Once we get full C++14 support we want this + // assert(integer_range_constraint >= RANGE_VALID && + // integer_range_constraint <= RANGE_INVALID) + return static_cast<RangeConstraint>(integer_range_constraint); +} + +// This function creates a RangeConstraint from an upper and lower bound +// check by taking advantage of the fact that only NaN can be out of range in +// both directions at once. +constexpr inline RangeConstraint GetRangeConstraint(bool is_in_upper_bound, bool is_in_lower_bound) +{ + return GetRangeConstraint((is_in_upper_bound ? 0 : RANGE_OVERFLOW) | + (is_in_lower_bound ? 0 : RANGE_UNDERFLOW)); +} + +// The following helper template addresses a corner case in range checks for +// conversion from a floating-point type to an integral type of smaller range +// but larger precision (e.g. float -> unsigned). The problem is as follows: +// 1. Integral maximum is always one less than a power of two, so it must be +// truncated to fit the mantissa of the floating point. The direction of +// rounding is implementation defined, but by default it's always IEEE +// floats, which round to nearest and thus result in a value of larger +// magnitude than the integral value. +// Example: float f = UINT_MAX; // f is 4294967296f but UINT_MAX +// // is 4294967295u. +// 2. If the floating point value is equal to the promoted integral maximum +// value, a range check will erroneously pass. +// Example: (4294967296f <= 4294967295u) // This is true due to a precision +// // loss in rounding up to float. +// 3. When the floating point value is then converted to an integral, the +// resulting value is out of range for the target integral type and +// thus is implementation defined. +// Example: unsigned u = (float)INT_MAX; // u will typically overflow to 0. +// To fix this bug we manually truncate the maximum value when the destination +// type is an integral of larger precision than the source floating-point type, +// such that the resulting maximum is represented exactly as a floating point. +template <typename Dst, typename Src> +struct NarrowingRange +{ + typedef typename std::numeric_limits<Src> SrcLimits; + typedef typename std::numeric_limits<Dst> DstLimits; + // The following logic avoids warnings where the max function is + // instantiated with invalid values for a bit shift (even though + // such a function can never be called). + static const int shift = (MaxExponent<Src>::value > MaxExponent<Dst>::value && + SrcLimits::digits < DstLimits::digits && + SrcLimits::is_iec559 && + DstLimits::is_integer) + ? (DstLimits::digits - SrcLimits::digits) + : 0; + + static constexpr Dst max() + { + // We use UINTMAX_C below to avoid compiler warnings about shifting floating + // points. Since it's a compile time calculation, it shouldn't have any + // performance impact. + return DstLimits::max() - static_cast<Dst>((UINTMAX_C(1) << shift) - 1); + } + + static constexpr Dst min() + { + return std::numeric_limits<Dst>::is_iec559 ? -DstLimits::max() : DstLimits::min(); + } +}; + +template <typename Dst, + typename Src, + IntegerRepresentation DstSign = std::numeric_limits<Dst>::is_signed + ? INTEGER_REPRESENTATION_SIGNED + : INTEGER_REPRESENTATION_UNSIGNED, + IntegerRepresentation SrcSign = std::numeric_limits<Src>::is_signed + ? INTEGER_REPRESENTATION_SIGNED + : INTEGER_REPRESENTATION_UNSIGNED, + NumericRangeRepresentation DstRange = StaticDstRangeRelationToSrcRange<Dst, Src>::value> +struct DstRangeRelationToSrcRangeImpl; + +// The following templates are for ranges that must be verified at runtime. We +// split it into checks based on signedness to avoid confusing casts and +// compiler warnings on signed an unsigned comparisons. + +// Dst range is statically determined to contain Src: Nothing to check. +template <typename Dst, typename Src, IntegerRepresentation DstSign, IntegerRepresentation SrcSign> +struct DstRangeRelationToSrcRangeImpl<Dst, Src, DstSign, SrcSign, NUMERIC_RANGE_CONTAINED> +{ + static constexpr RangeConstraint Check(Src value) { return RANGE_VALID; } +}; + +// Signed to signed narrowing: Both the upper and lower boundaries may be +// exceeded. +template <typename Dst, typename Src> +struct DstRangeRelationToSrcRangeImpl<Dst, + Src, + INTEGER_REPRESENTATION_SIGNED, + INTEGER_REPRESENTATION_SIGNED, + NUMERIC_RANGE_NOT_CONTAINED> +{ + static constexpr RangeConstraint Check(Src value) + { + return GetRangeConstraint((value <= NarrowingRange<Dst, Src>::max()), + (value >= NarrowingRange<Dst, Src>::min())); + } +}; + +// Unsigned to unsigned narrowing: Only the upper boundary can be exceeded. +template <typename Dst, typename Src> +struct DstRangeRelationToSrcRangeImpl<Dst, + Src, + INTEGER_REPRESENTATION_UNSIGNED, + INTEGER_REPRESENTATION_UNSIGNED, + NUMERIC_RANGE_NOT_CONTAINED> +{ + static constexpr RangeConstraint Check(Src value) + { + return GetRangeConstraint(value <= NarrowingRange<Dst, Src>::max(), true); + } +}; + +// Unsigned to signed: The upper boundary may be exceeded. +template <typename Dst, typename Src> +struct DstRangeRelationToSrcRangeImpl<Dst, + Src, + INTEGER_REPRESENTATION_SIGNED, + INTEGER_REPRESENTATION_UNSIGNED, + NUMERIC_RANGE_NOT_CONTAINED> +{ + static constexpr RangeConstraint Check(Src value) + { + return sizeof(Dst) > sizeof(Src) + ? RANGE_VALID + : GetRangeConstraint(value <= static_cast<Src>(NarrowingRange<Dst, Src>::max()), + true); + } +}; + +// Signed to unsigned: The upper boundary may be exceeded for a narrower Dst, +// and any negative value exceeds the lower boundary. +template <typename Dst, typename Src> +struct DstRangeRelationToSrcRangeImpl<Dst, + Src, + INTEGER_REPRESENTATION_UNSIGNED, + INTEGER_REPRESENTATION_SIGNED, + NUMERIC_RANGE_NOT_CONTAINED> +{ + static constexpr RangeConstraint Check(Src value) + { + return (MaxExponent<Dst>::value >= MaxExponent<Src>::value) + ? GetRangeConstraint(true, value >= static_cast<Src>(0)) + : GetRangeConstraint(value <= static_cast<Src>(NarrowingRange<Dst, Src>::max()), + value >= static_cast<Src>(0)); + } +}; + +template <typename Dst, typename Src> +constexpr RangeConstraint DstRangeRelationToSrcRange(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."); + return DstRangeRelationToSrcRangeImpl<Dst, Src>::Check(value); +} + +} // namespace internal +} // namespace base + +} // namespace angle + +#endif // ANGLEBASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ |