зеркало из https://github.com/mozilla/gecko-dev.git
115 строки
4.1 KiB
C++
115 строки
4.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
#ifndef mozilla_FunctionTypeTraits_h
|
|
#define mozilla_FunctionTypeTraits_h
|
|
|
|
#include <cstddef> /* for size_t */
|
|
#include <tuple>
|
|
|
|
namespace mozilla {
|
|
|
|
// Main FunctionTypeTraits declaration, taking one template argument.
|
|
//
|
|
// Given a function type, FunctionTypeTraits will expose the following members:
|
|
// - ReturnType: Return type.
|
|
// - arity: Number of parameters (size_t).
|
|
// - ParameterType<N>: Type of the Nth** parameter, 0-indexed.
|
|
//
|
|
// ** `ParameterType<N>` with `N` >= `arity` is allowed and gives `void`.
|
|
// This prevents compilation errors when trying to access a type outside of the
|
|
// function's parameters, which is useful for parameters checks, e.g.:
|
|
// template<typename F>
|
|
// auto foo(F&&)
|
|
// -> enable_if(FunctionTypeTraits<F>::arity == 1 &&
|
|
// is_same<FunctionTypeTraits<F>::template ParameterType<0>,
|
|
// int>::value,
|
|
// void)
|
|
// {
|
|
// // This function will only be enabled if `F` takes one `int`.
|
|
// // Without the permissive ParameterType<any N>, it wouldn't even compile.
|
|
//
|
|
// Note: FunctionTypeTraits does not work with generic lambdas `[](auto&) {}`,
|
|
// because parameter types cannot be known until an actual invocation when types
|
|
// are inferred from the given arguments.
|
|
template <typename T>
|
|
struct FunctionTypeTraits;
|
|
|
|
// Remove reference and pointer wrappers, if any.
|
|
template <typename T>
|
|
struct FunctionTypeTraits<T&> : public FunctionTypeTraits<T> {};
|
|
template <typename T>
|
|
struct FunctionTypeTraits<T&&> : public FunctionTypeTraits<T> {};
|
|
template <typename T>
|
|
struct FunctionTypeTraits<T*> : public FunctionTypeTraits<T> {};
|
|
|
|
// Extract `operator()` function from callables (e.g. lambdas, std::function).
|
|
template <typename T>
|
|
struct FunctionTypeTraits
|
|
: public FunctionTypeTraits<decltype(&T::operator())> {};
|
|
|
|
namespace detail {
|
|
|
|
// If `safe`, retrieve the `N`th type from `As`, otherwise `void`.
|
|
// See top description for reason.
|
|
template <bool safe, size_t N, typename... As>
|
|
struct TupleElementSafe;
|
|
template <size_t N, typename... As>
|
|
struct TupleElementSafe<true, N, As...> {
|
|
using Type = typename std::tuple_element<N, std::tuple<As...>>::type;
|
|
};
|
|
template <size_t N, typename... As>
|
|
struct TupleElementSafe<false, N, As...> {
|
|
using Type = void;
|
|
};
|
|
|
|
template <typename R, typename... As>
|
|
struct FunctionTypeTraitsHelper {
|
|
using ReturnType = R;
|
|
static constexpr size_t arity = sizeof...(As);
|
|
template <size_t N>
|
|
using ParameterType =
|
|
typename TupleElementSafe<(N < sizeof...(As)), N, As...>::Type;
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
// Specialization for free functions.
|
|
template <typename R, typename... As>
|
|
struct FunctionTypeTraits<R(As...)>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
|
|
// Specialization for non-const member functions.
|
|
template <typename C, typename R, typename... As>
|
|
struct FunctionTypeTraits<R (C::*)(As...)>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
|
|
// Specialization for const member functions.
|
|
template <typename C, typename R, typename... As>
|
|
struct FunctionTypeTraits<R (C::*)(As...) const>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
|
|
#ifdef NS_HAVE_STDCALL
|
|
// Specialization for __stdcall free functions.
|
|
template <typename R, typename... As>
|
|
struct FunctionTypeTraits<R NS_STDCALL(As...)>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
|
|
// Specialization for __stdcall non-const member functions.
|
|
template <typename C, typename R, typename... As>
|
|
struct FunctionTypeTraits<R (NS_STDCALL C::*)(As...)>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
|
|
// Specialization for __stdcall const member functions.
|
|
template <typename C, typename R, typename... As>
|
|
struct FunctionTypeTraits<R (NS_STDCALL C::*)(As...) const>
|
|
: detail::FunctionTypeTraitsHelper<R, As...> {};
|
|
#endif // NS_HAVE_STDCALL
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif // mozilla_FunctionTypeTraits_h
|