70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
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/* SPDX-License-Identifier: GPL-3.0-or-later
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* Copyright © 2022 The TokTok team.
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*/
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#ifndef C_TOXCORE_TESTING_FUZZING_FUNC_CONVERSION_H
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#define C_TOXCORE_TESTING_FUZZING_FUNC_CONVERSION_H
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namespace detail {
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template <typename F, F f>
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struct func_conversion {
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private:
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template <typename R, typename... Args>
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using func_pointer = R (*)(Args...);
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template <typename From>
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struct static_caster {
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From obj;
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template <typename To>
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operator To() const
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{
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return static_cast<To>(obj);
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}
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};
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public:
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template <typename R, typename Arg, typename... Args>
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constexpr operator func_pointer<R, Arg, Args...>()
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{
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return [](Arg obj, auto... args) { return f(static_caster<Arg>{obj}, args...); };
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}
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};
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template <typename F>
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struct make_funptr;
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template <typename T, typename R, typename... Args>
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struct make_funptr<R (T::*)(Args...) const> {
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using type = R (*)(Args...);
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};
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/** @brief Turn a memfunptr type into a plain funptr type.
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*
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* Not needed in C++20, because we can pass the lambda itself as template
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* argument, but in C++17, we need to do an early conversion.
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*/
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template <typename F>
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using make_funptr_t = typename make_funptr<F>::type;
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}
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/** @brief Turn a C++ lambda into a C function pointer with `void*` param.
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*
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* Takes a lambda function with any pointer type as first parameter and turns it
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* into a C function pointer with `void*` as the first parameter. Internally, it
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* `static_cast`s that `void*` to the lambda's parameter type, avoiding a bunch
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* of casts inside the lambdas.
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*
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* This works on any type `T` that can be `static_cast` to `U`, not just `void*`
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* to `U*`, but the common case for C callbacks is `void*`.
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*/
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template <typename F>
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static constexpr auto operator!(F f)
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{
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return detail::func_conversion<detail::make_funptr_t<decltype(&F::operator())>, f>{};
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}
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#endif // C_TOXCORE_TESTING_FUZZING_FUNC_CONVERSION_H
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