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New narrow() implementation

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This commit is contained in:
Nekotekina 2016-08-14 20:22:07 +03:00
parent 0f87c4485d
commit b0f5796c90
2 changed files with 114 additions and 19 deletions
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101
Utilities/types.h
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@ -574,19 +574,110 @@ inline std::remove_reference_t<T>&& verify_move(T&& value, const char* cause, F&
return std::move(value);
}
// Narrow cast (throws on failure)
// narrow() function details
template <typename From, typename To = void, typename = void>
struct narrow_impl
{
// Temporarily (diagnostic)
static_assert(std::is_void<To>::value, "narrow_impl<> specialization not found");
// Returns true if value cannot be represented in type To
static constexpr bool test(const From& value)
{
// Unspecialized cases (including cast to void) always considered narrowing
return true;
}
};
// Unsigned to unsigned narrowing
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_unsigned<From>::value && std::is_unsigned<To>::value>>
{
static constexpr bool test(const From& value)
{
return sizeof(To) < sizeof(From) && static_cast<To>(value) != value;
}
};
// Signed to signed narrowing
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_signed<From>::value && std::is_signed<To>::value>>
{
static constexpr bool test(const From& value)
{
return sizeof(To) < sizeof(From) && static_cast<To>(value) != value;
}
};
// Unsigned to signed narrowing
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_unsigned<From>::value && std::is_signed<To>::value>>
{
static constexpr bool test(const From& value)
{
return sizeof(To) <= sizeof(From) && value > (static_cast<std::make_unsigned_t<To>>(-1) >> 1);
}
};
// Signed to unsigned narrowing (I)
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_signed<From>::value && std::is_unsigned<To>::value && sizeof(To) >= sizeof(From)>>
{
static constexpr bool test(const From& value)
{
return value < static_cast<From>(0);
}
};
// Signed to unsigned narrowing (II)
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_signed<From>::value && std::is_unsigned<To>::value && sizeof(To) < sizeof(From)>>
{
static constexpr bool test(const From& value)
{
return static_cast<std::make_unsigned_t<From>>(value) > static_cast<To>(-1);
}
};
// Enum to integer (TODO?)
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_enum<From>::value && std::is_integral<To>::value>>
: narrow_impl<std::underlying_type_t<From>, To>
{
};
// Integer to enum (TODO?)
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_integral<From>::value && std::is_enum<To>::value>>
: narrow_impl<From, std::underlying_type_t<To>>
{
};
// Enum to enum (TODO?)
template <typename From, typename To>
struct narrow_impl<From, To, std::enable_if_t<std::is_enum<From>::value && std::is_enum<To>::value>>
: narrow_impl<std::underlying_type_t<From>, std::underlying_type_t<To>>
{
};
// Simple type enabled (TODO?)
template <typename From, typename To>
struct narrow_impl<From, To, void_t<typename From::simple_type>>
: narrow_impl<simple_t<From>, To>
{
};
template <typename To = void, typename From, typename = decltype(static_cast<To>(std::declval<From>()))>
inline To narrow(const From& value, const char* msg = nullptr)
{
// Allow "narrowing to void" and ensure it always fails in this case
auto&& result = static_cast<std::conditional_t<std::is_void<To>::value, From, To>>(value);
if (std::is_void<To>::value || static_cast<From>(result) != value)
// Narrow check
if (narrow_impl<From, To>::test(value))
{
// Pack value as formatting argument
fmt::raw_narrow_error(msg, fmt::get_type_info<typename fmt_unveil<From>::type>(), fmt_unveil<From>::get(value));
}
return static_cast<std::conditional_t<std::is_void<To>::value, void, decltype(result)>>(result);
return static_cast<To>(value);
}
// Returns u32 size() for container