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370 lines
19 KiB
C++
370 lines
19 KiB
C++
//*********************************************************
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//
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// Copyright (c) Microsoft. All rights reserved.
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// This code is licensed under the MIT License.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
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// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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// PARTICULAR PURPOSE AND NONINFRINGEMENT.
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//
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//*********************************************************
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#ifndef __WIL_SAFECAST_INCLUDED
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#define __WIL_SAFECAST_INCLUDED
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#include "result_macros.h"
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#include <intsafe.h>
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#include "wistd_config.h"
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#include "wistd_type_traits.h"
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namespace wil
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{
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namespace details
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{
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// Default error case for undefined conversions in intsafe.h
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template<typename OldT, typename NewT> constexpr wistd::nullptr_t intsafe_conversion = nullptr;
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// is_known_safe_static_cast_v determines if a conversion is known to be safe or not. Known
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// safe conversions can be handled by static_cast, this includes conversions between the same
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// type, when the new type is larger than the old type but is not a signed to unsigned
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// conversion, and when the two types are the same size and signed/unsigned. All other
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// conversions will be assumed to be potentially unsafe, and the conversion must be handled
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// by intsafe and checked.
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template <typename NewT, typename OldT>
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constexpr bool is_known_safe_static_cast_v =
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(sizeof(NewT) > sizeof(OldT) && !(wistd::is_signed_v<OldT> && wistd::is_unsigned_v<NewT>)) ||
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(sizeof(NewT) == sizeof(OldT) && ((wistd::is_signed_v<NewT> && wistd::is_signed_v<OldT>) || (wistd::is_unsigned_v<NewT> && wistd::is_unsigned_v<OldT>)));
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// Helper template to determine that NewT and OldT are both integral types. The safe_cast
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// operation only supports conversions between integral types.
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template <typename NewT, typename OldT>
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constexpr bool both_integral_v = wistd::is_integral<NewT>::value && wistd::is_integral<OldT>::value;
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// Note on native wchar_t (__wchar_t):
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// Intsafe.h does not currently handle native wchar_t. When compiling with /Zc:wchar_t-, this is fine as wchar_t is
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// typedef'd to unsigned short. However, when compiling with /Zc:wchar_t or wchar_t as a native type, the lack of
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// support for native wchar_t in intsafe.h becomes an issue. To work around this, we treat native wchar_t as an
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// unsigned short when passing it to intsafe.h, because the two on the Windows platform are the same size and
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// share the same range according to MSDN. If the cast is to a native wchar_t, the result from intsafe.h is cast
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// to a native wchar_t.
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// Intsafe does not have a defined conversion for native wchar_t
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template <typename NewT, typename OldT>
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constexpr bool neither_native_wchar_v = !wistd::is_same<NewT, __wchar_t>::value && !wistd::is_same<OldT, __wchar_t>::value;
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// Check to see if the cast is a conversion to native wchar_t
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template <typename NewT, typename OldT>
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constexpr bool is_cast_to_wchar_v = wistd::is_same<NewT, __wchar_t>::value && !wistd::is_same<OldT, __wchar_t>::value;
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// Check to see if the cast is a conversion from native wchar_t
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template <typename NewT, typename OldT>
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constexpr bool is_cast_from_wchar_v = !wistd::is_same<NewT, __wchar_t>::value && wistd::is_same<OldT, __wchar_t>::value;
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// Validate the conversion to be performed has a defined mapping to an intsafe conversion
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template <typename NewT, typename OldT>
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constexpr bool is_supported_intsafe_cast_v = intsafe_conversion<OldT, NewT> != nullptr;
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// True when the conversion is between integral types and can be handled by static_cast
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template <typename NewT, typename OldT>
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constexpr bool is_supported_safe_static_cast_v = both_integral_v<NewT, OldT> && is_known_safe_static_cast_v<NewT, OldT>;
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// True when the conversion is between integral types, does not involve native wchar, has
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// a mapped intsafe conversion, and is unsafe.
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template <typename NewT, typename OldT>
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constexpr bool is_supported_unsafe_cast_no_wchar_v =
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both_integral_v<NewT, OldT> &&
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!is_known_safe_static_cast_v<NewT, OldT> &&
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neither_native_wchar_v<NewT, OldT> &&
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is_supported_intsafe_cast_v<NewT, OldT>;
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// True when the conversion is between integral types, is a cast to native wchar_t, has
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// a mapped intsafe conversion, and is unsafe.
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template <typename NewT, typename OldT>
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constexpr bool is_supported_unsafe_cast_to_wchar_v =
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both_integral_v<NewT, OldT> &&
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!is_known_safe_static_cast_v<NewT, OldT> &&
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is_cast_to_wchar_v<NewT, OldT> &&
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is_supported_intsafe_cast_v<unsigned short, OldT>;
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// True when the conversion is between integral types, is a cast from native wchar_t, has
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// a mapped intsafe conversion, and is unsafe.
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template <typename NewT, typename OldT>
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constexpr bool is_supported_unsafe_cast_from_wchar_v =
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both_integral_v<NewT, OldT> &&
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!is_known_safe_static_cast_v<NewT, OldT> &&
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is_cast_from_wchar_v<NewT, OldT> &&
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is_supported_intsafe_cast_v<NewT, unsigned short>;
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// True when the conversion is supported and unsafe, and may or may not involve
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// native wchar_t.
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template <typename NewT, typename OldT>
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constexpr bool is_supported_unsafe_cast_v =
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is_supported_unsafe_cast_no_wchar_v<NewT, OldT> ||
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is_supported_unsafe_cast_to_wchar_v<NewT, OldT> ||
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is_supported_unsafe_cast_from_wchar_v<NewT, OldT>;
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// True when T is any one of the primitive types that the variably sized types are defined as.
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template <typename T>
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constexpr bool is_potentially_variably_sized_type_v =
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wistd::is_same<T, int>::value ||
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wistd::is_same<T, unsigned int>::value ||
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wistd::is_same<T, long>::value ||
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wistd::is_same<T, unsigned long>::value ||
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wistd::is_same<T, __int64>::value ||
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wistd::is_same<T, unsigned __int64>::value;
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// True when either type is potentialy variably sized (e.g. size_t, ptrdiff_t)
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template <typename OldT, typename NewT>
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constexpr bool is_potentially_variably_sized_cast_v =
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is_potentially_variably_sized_type_v<OldT> ||
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is_potentially_variably_sized_type_v<NewT>;
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// Mappings of all conversions defined in intsafe.h to intsafe_conversion
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// Note: Uppercase types (UINT, DWORD, SIZE_T, etc) and architecture dependent types resolve
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// to the base types. The base types are used since they do not vary based on architecture.
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template<> constexpr auto intsafe_conversion<__int64, char> = LongLongToChar;
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template<> constexpr auto intsafe_conversion<__int64, int> = LongLongToInt;
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template<> constexpr auto intsafe_conversion<__int64, long> = LongLongToLong;
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template<> constexpr auto intsafe_conversion<__int64, short> = LongLongToShort;
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template<> constexpr auto intsafe_conversion<__int64, signed char> = LongLongToInt8;
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template<> constexpr auto intsafe_conversion<__int64, unsigned __int64> = LongLongToULongLong;
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template<> constexpr auto intsafe_conversion<__int64, unsigned char> = LongLongToUChar;
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template<> constexpr auto intsafe_conversion<__int64, unsigned int> = LongLongToUInt;
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template<> constexpr auto intsafe_conversion<__int64, unsigned long> = LongLongToULong;
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template<> constexpr auto intsafe_conversion<__int64, unsigned short> = LongLongToUShort;
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template<> constexpr auto intsafe_conversion<int, char> = IntToChar;
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template<> constexpr auto intsafe_conversion<int, short> = IntToShort;
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template<> constexpr auto intsafe_conversion<int, signed char> = IntToInt8;
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template<> constexpr auto intsafe_conversion<int, unsigned __int64> = IntToULongLong;
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template<> constexpr auto intsafe_conversion<int, unsigned char> = IntToUChar;
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template<> constexpr auto intsafe_conversion<int, unsigned int> = IntToUInt;
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template<> constexpr auto intsafe_conversion<int, unsigned long> = IntToULong;
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template<> constexpr auto intsafe_conversion<int, unsigned short> = IntToUShort;
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template<> constexpr auto intsafe_conversion<long, char> = LongToChar;
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template<> constexpr auto intsafe_conversion<long, int> = LongToInt;
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template<> constexpr auto intsafe_conversion<long, short> = LongToShort;
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template<> constexpr auto intsafe_conversion<long, signed char> = LongToInt8;
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template<> constexpr auto intsafe_conversion<long, unsigned __int64> = LongToULongLong;
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template<> constexpr auto intsafe_conversion<long, unsigned char> = LongToUChar;
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template<> constexpr auto intsafe_conversion<long, unsigned int> = LongToUInt;
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template<> constexpr auto intsafe_conversion<long, unsigned long> = LongToULong;
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template<> constexpr auto intsafe_conversion<long, unsigned short> = LongToUShort;
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template<> constexpr auto intsafe_conversion<short, char> = ShortToChar;
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template<> constexpr auto intsafe_conversion<short, signed char> = ShortToInt8;
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template<> constexpr auto intsafe_conversion<short, unsigned __int64> = ShortToULongLong;
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template<> constexpr auto intsafe_conversion<short, unsigned char> = ShortToUChar;
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template<> constexpr auto intsafe_conversion<short, unsigned int> = ShortToUInt;
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template<> constexpr auto intsafe_conversion<short, unsigned long> = ShortToULong;
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template<> constexpr auto intsafe_conversion<short, unsigned short> = ShortToUShort;
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template<> constexpr auto intsafe_conversion<signed char, unsigned __int64> = Int8ToULongLong;
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template<> constexpr auto intsafe_conversion<signed char, unsigned char> = Int8ToUChar;
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template<> constexpr auto intsafe_conversion<signed char, unsigned int> = Int8ToUInt;
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template<> constexpr auto intsafe_conversion<signed char, unsigned long> = Int8ToULong;
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template<> constexpr auto intsafe_conversion<signed char, unsigned short> = Int8ToUShort;
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template<> constexpr auto intsafe_conversion<unsigned __int64, __int64> = ULongLongToLongLong;
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template<> constexpr auto intsafe_conversion<unsigned __int64, char> = ULongLongToChar;
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template<> constexpr auto intsafe_conversion<unsigned __int64, int> = ULongLongToInt;
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template<> constexpr auto intsafe_conversion<unsigned __int64, long> = ULongLongToLong;
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template<> constexpr auto intsafe_conversion<unsigned __int64, short> = ULongLongToShort;
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template<> constexpr auto intsafe_conversion<unsigned __int64, signed char> = ULongLongToInt8;
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template<> constexpr auto intsafe_conversion<unsigned __int64, unsigned char> = ULongLongToUChar;
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template<> constexpr auto intsafe_conversion<unsigned __int64, unsigned int> = ULongLongToUInt;
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template<> constexpr auto intsafe_conversion<unsigned __int64, unsigned long> = ULongLongToULong;
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template<> constexpr auto intsafe_conversion<unsigned __int64, unsigned short> = ULongLongToUShort;
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template<> constexpr auto intsafe_conversion<unsigned char, char> = UInt8ToChar;
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template<> constexpr auto intsafe_conversion<unsigned char, signed char> = UIntToInt8;
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template<> constexpr auto intsafe_conversion<unsigned int, char> = UIntToChar;
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template<> constexpr auto intsafe_conversion<unsigned int, int> = UIntToInt;
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template<> constexpr auto intsafe_conversion<unsigned int, long> = UIntToLong;
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template<> constexpr auto intsafe_conversion<unsigned int, short> = UIntToShort;
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template<> constexpr auto intsafe_conversion<unsigned int, signed char> = UIntToInt8;
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template<> constexpr auto intsafe_conversion<unsigned int, unsigned char> = UIntToUChar;
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template<> constexpr auto intsafe_conversion<unsigned int, unsigned short> = UIntToUShort;
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template<> constexpr auto intsafe_conversion<unsigned long, char> = ULongToChar;
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template<> constexpr auto intsafe_conversion<unsigned long, int> = ULongToInt;
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template<> constexpr auto intsafe_conversion<unsigned long, long> = ULongToLong;
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template<> constexpr auto intsafe_conversion<unsigned long, short> = ULongToShort;
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template<> constexpr auto intsafe_conversion<unsigned long, signed char> = ULongToInt8;
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template<> constexpr auto intsafe_conversion<unsigned long, unsigned char> = ULongToUChar;
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template<> constexpr auto intsafe_conversion<unsigned long, unsigned int> = ULongToUInt;
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template<> constexpr auto intsafe_conversion<unsigned long, unsigned short> = ULongToUShort;
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template<> constexpr auto intsafe_conversion<unsigned short, char> = UShortToChar;
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template<> constexpr auto intsafe_conversion<unsigned short, short> = UShortToShort;
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template<> constexpr auto intsafe_conversion<unsigned short, signed char> = UShortToInt8;
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template<> constexpr auto intsafe_conversion<unsigned short, unsigned char> = UShortToUChar;
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}
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// Unsafe conversion where failure results in fail fast.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_no_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_failfast(const OldT var)
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{
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NewT newVar;
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FAIL_FAST_IF_FAILED((details::intsafe_conversion<OldT, NewT>(var, &newVar)));
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return newVar;
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}
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// Unsafe conversion where failure results in fail fast.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_from_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_failfast(const OldT var)
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{
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NewT newVar;
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FAIL_FAST_IF_FAILED((details::intsafe_conversion<unsigned short, NewT>(static_cast<unsigned short>(var), &newVar)));
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return newVar;
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}
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// Unsafe conversion where failure results in fail fast.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_to_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_failfast(const OldT var)
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{
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unsigned short newVar;
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FAIL_FAST_IF_FAILED((details::intsafe_conversion<OldT, unsigned short>(var, &newVar)));
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return static_cast<__wchar_t>(newVar);
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}
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// This conversion is always safe, therefore a static_cast is fine.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_safe_static_cast_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_failfast(const OldT var)
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{
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return static_cast<NewT>(var);
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}
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#ifdef WIL_ENABLE_EXCEPTIONS
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// Unsafe conversion where failure results in a thrown exception.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_no_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast(const OldT var)
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{
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NewT newVar;
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THROW_IF_FAILED((details::intsafe_conversion<OldT, NewT>(var, &newVar)));
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return newVar;
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}
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// Unsafe conversion where failure results in a thrown exception.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_from_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast(const OldT var)
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{
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NewT newVar;
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THROW_IF_FAILED((details::intsafe_conversion<unsigned short, NewT>(static_cast<unsigned short>(var), &newVar)));
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return newVar;
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}
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// Unsafe conversion where failure results in a thrown exception.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_to_wchar_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast(const OldT var)
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{
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unsigned short newVar;
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THROW_IF_FAILED((details::intsafe_conversion<OldT, unsigned short>(var, &newVar)));
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return static_cast<__wchar_t>(newVar);
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}
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// This conversion is always safe, therefore a static_cast is fine.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_safe_static_cast_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast(const OldT var)
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{
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return static_cast<NewT>(var);
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}
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#endif
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// This conversion is unsafe, therefore the two parameter version of safe_cast_nothrow must be used
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_nothrow(const OldT /*var*/)
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{
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static_assert(!wistd::is_same_v<NewT, NewT>, "This cast has the potential to fail, use the two parameter safe_cast_nothrow instead");
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}
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// This conversion is always safe, therefore a static_cast is fine.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_safe_static_cast_v<NewT, OldT>, int> = 0
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>
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NewT safe_cast_nothrow(const OldT var)
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{
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return static_cast<NewT>(var);
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}
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// Unsafe conversion where an HRESULT is returned. It is up to the callee to check and handle the HRESULT
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_no_wchar_v<NewT, OldT>, int> = 0
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>
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HRESULT safe_cast_nothrow(const OldT var, NewT* newTResult)
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{
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return details::intsafe_conversion<OldT, NewT>(var, newTResult);
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}
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// Unsafe conversion where an HRESULT is returned. It is up to the callee to check and handle the HRESULT
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_from_wchar_v<NewT, OldT>, int> = 0
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>
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HRESULT safe_cast_nothrow(const OldT var, NewT* newTResult)
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{
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return details::intsafe_conversion<unsigned short, NewT>(static_cast<unsigned short>(var), newTResult);
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}
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// Unsafe conversion where an HRESULT is returned. It is up to the callee to check and handle the HRESULT
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_unsafe_cast_to_wchar_v<NewT, OldT>, int> = 0
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>
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HRESULT safe_cast_nothrow(const OldT var, NewT* newTResult)
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{
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return details::intsafe_conversion<OldT, unsigned short>(var, reinterpret_cast<unsigned short *>(newTResult));
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}
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// This conversion is always safe, therefore a static_cast is fine. If it can be determined the conversion
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// does not involve a variably sized type, then the compilation will fail and say the single parameter version
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// of safe_cast_nothrow should be used instead.
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template <
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typename NewT,
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typename OldT,
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wistd::enable_if_t<details::is_supported_safe_static_cast_v<NewT, OldT>, int> = 0
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>
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HRESULT safe_cast_nothrow(const OldT var, NewT* newTResult)
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{
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static_assert(details::is_potentially_variably_sized_cast_v<OldT, NewT>, "This cast is always safe; use safe_cast_nothrow<T>(value) to avoid unnecessary error handling.");
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*newTResult = static_cast<NewT>(var);
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return S_OK;
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}
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}
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#endif // __WIL_SAFECAST_INCLUDED
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