chromium/third_party/dawn/src/tint/utils/traits/traits.h

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#ifndef SRC_TINT_UTILS_TRAITS_TRAITS_H_
#define SRC_TINT_UTILS_TRAITS_TRAITS_H_

#include <ostream>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>

namespace tint::traits {

/// Convience type definition for std::decay<T>::type
Decay;

/// NthTypeOf returns the `N`th type in `Types`
NthTypeOf;

/// Signature describes the signature of a function.
template <typename RETURN, typename... PARAMETERS>
struct Signature { … };

/// SignatureOf is a traits helper that infers the signature of the function,
/// method, static method, lambda, or function-like object `F`.
template <typename F>
struct SignatureOf { … };

/// SignatureOf specialization for a regular function or static method.
SignatureOf<R (*)(ARGS...)>;

/// SignatureOf specialization for a non-static method.
SignatureOf<R (C::*)(ARGS...)>;

/// SignatureOf specialization for a non-static, const method.
SignatureOf<R (C::*)(ARGS...) const>;

/// SignatureOfT is an alias to `typename SignatureOf<F>::type`.
SignatureOfT;

/// ParameterType is an alias to `typename SignatureOf<F>::type::parameter<N>`.
ParameterType;

/// LastParameterType returns the type of the last parameter of `F`. `F` must have at least one
/// parameter.
LastParameterType;

/// ReturnType is an alias to `typename SignatureOf<F>::type::ret`.
ReturnType;

/// Returns true iff decayed T and decayed U are the same.
IsType;

/// IsTypeOrDerived<T, BASE> is true iff `T` is of type `BASE`, or derives from
/// `BASE`.
IsTypeOrDerived;

/// If `CONDITION` is true then EnableIf resolves to type T, otherwise an invalid type.
EnableIf;

/// If `T` is of type `BASE`, or derives from `BASE`, then EnableIfIsType
/// resolves to type `T`, otherwise an invalid type.
EnableIfIsType;

/// @returns the std::index_sequence with all the indices shifted by OFFSET.
template <std::size_t OFFSET, std::size_t... INDICES>
constexpr auto Shift(std::index_sequence<INDICES...>) { … }

/// @returns a std::integer_sequence with the integers `[OFFSET..OFFSET+COUNT)`
template <std::size_t OFFSET, std::size_t COUNT>
constexpr auto Range() { … }

namespace detail {

/// @returns the tuple `t` swizzled by `INDICES`
template <typename TUPLE, std::size_t... INDICES>
constexpr auto Swizzle(TUPLE&& t, std::index_sequence<INDICES...>)
    -> std::tuple<std::tuple_element_t<INDICES, std::remove_reference_t<TUPLE>>...> { … }

/// @returns a nullptr of the tuple type `TUPLE` swizzled by `INDICES`.
/// @note: This function is intended to be used in a `decltype()` expression,
/// and returns a pointer-to-tuple as the tuple may hold non-constructable
/// types.
template <typename TUPLE, std::size_t... INDICES>
constexpr auto* SwizzlePtrTy(std::index_sequence<INDICES...>) { … }

}  // namespace detail

/// @returns the slice of the tuple `t` with the tuple elements
/// `[OFFSET..OFFSET+COUNT)`
template <std::size_t OFFSET, std::size_t COUNT, typename TUPLE>
constexpr auto Slice(TUPLE&& t) { … }

/// Resolves to the slice of the tuple `t` with the tuple elements
/// `[OFFSET..OFFSET+COUNT)`
SliceTuple;

namespace detail {
/// Base template for IsTypeIn
template <typename T, typename TypeList>
struct IsTypeIn;

/// Specialization for IsTypeIn
IsTypeIn<T, TypeContainer<Ts...>>;
}  // namespace detail

/// Evaluates to true if T is one of the types in the TypeContainer's template arguments.
/// Works for std::variant, std::tuple, std::pair, or any typename template where all parameters are
/// types.
IsTypeIn;

/// Evaluates to the decayed pointer element type, or the decayed type T if T is not a pointer.
PtrElTy;

/// Evaluates to true if `T` decayed is a `std::string`, `std::string_view`, `const char*` or
/// `char*`
IsStringLike;

namespace detail {
/// Helper for CharArrayToCharPtr
template <typename T>
struct CharArrayToCharPtrImpl { … };
/// Specialization of CharArrayToCharPtrImpl for `char[N]`
CharArrayToCharPtrImpl<char[N]>;
/// Specialization of CharArrayToCharPtrImpl for `const char[N]`
CharArrayToCharPtrImpl<const char[N]>;
}  // namespace detail

/// Evaluates to `char*` or `const char*` if `T` is `char[N]` or `const char[N]`, respectively,
/// otherwise T.
CharArrayToCharPtr;

////////////////////////////////////////////////////////////////////////////////
// IsOStream
////////////////////////////////////////////////////////////////////////////////
namespace detail {
/// Helper for determining whether the type T can be used as a stream writer
template <typename T, typename ENABLE = void>
struct IsOStream : std::false_type { … };

/// Specialization for types that declare a `static constexpr bool IsStreamWriter` member
IsOStream<T, std::void_t<decltype(T::IsStreamWriter)>>;

/// Specialization for std::ostream
IsOStream<T, std::enable_if_t<std::is_same_v<T, std::ostream>>>;

/// Specialization for std::stringstream
IsOStream<T, std::enable_if_t<std::is_same_v<T, std::stringstream>>>;

}  // namespace detail

/// Is true if the class T can be treated as an output stream
IsOStream;

/// If `CONDITION` is true then EnableIfIsOStream resolves to type T, otherwise an invalid type.
EnableIfIsOStream;

////////////////////////////////////////////////////////////////////////////////
// HasOperatorShiftLeft
////////////////////////////////////////////////////////////////////////////////
namespace detail {
/// Helper for determining whether the operator<<(LHS, RHS) exists
template <typename LHS, typename RHS, typename = void>
struct HasOperatorShiftLeft : std::false_type { … };
/// Specialization to detect operator
HasOperatorShiftLeft<LHS, RHS, std::void_t<decltype(std::declval<LHS &>() << std::declval<RHS>())>>;

}  // namespace detail

/// Is true if operator<<(LHS, RHS) exists
HasOperatorShiftLeft;

}  // namespace tint::traits

#endif  // SRC_TINT_UTILS_TRAITS_TRAITS_H_