simplesync/include/nonstd_functional.hpp

/*
 * SPDX-License-Identifier: MIT
 * Copyright (c) 2019 winterscar
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifdef _NONSTD_FUNCTIONAL_HHP
#define _NONSTD_FUNCTIONAL_HHP
#include <Arduino.h>
// extern void * operator new(size_t size, void * ptr);
void* operator new(size_t size, void* ptr) {
    return ptr;
}
namespace nonstd {

template <class T>
struct tag {
    using type = T;
};
template <class Tag>
using type_t = typename Tag::type;

using size_t = decltype(sizeof(int));

// move

template <class T>
T&& move(T& t) {
    return static_cast<T&&>(t);
}

// forward

template <class T>
struct remove_reference : tag<T> {};
template <class T>
struct remove_reference<T&> : tag<T> {};
template <class T>
using remove_reference_t = type_t<remove_reference<T>>;

template <class T>
T&& forward(remove_reference_t<T>& t) {
    return static_cast<T&&>(t);
}
template <class T>
T&& forward(remove_reference_t<T>&& t) {
    return static_cast<T&&>(t);
}

// decay

template <class T>
struct remove_const : tag<T> {};
template <class T>
struct remove_const<T const> : tag<T> {};

template <class T>
struct remove_volatile : tag<T> {};
template <class T>
struct remove_volatile<T volatile> : tag<T> {};

template <class T>
struct remove_cv : remove_const<type_t<remove_volatile<T>>> {};

template <class T>
struct decay3 : remove_cv<T> {};
template <class R, class... Args>
struct decay3<R(Args...)> : tag<R (*)(Args...)> {};
template <class T>
struct decay2 : decay3<T> {};
template <class T, size_t N>
struct decay2<T[N]> : tag<T*> {};

template <class T>
struct decay : decay2<remove_reference_t<T>> {};

template <class T>
using decay_t = type_t<decay<T>>;

// is_convertible

template <class T>
T declval();  // no implementation

template <class T, T t>
struct integral_constant {
    static constexpr T value = t;
    constexpr integral_constant(){};
    constexpr operator T() const { return value; }
    constexpr T operator()() const { return value; }
};
template <bool b>
using bool_t = integral_constant<bool, b>;
using true_type = bool_t<true>;
using false_type = bool_t<false>;

template <class...>
struct voider : tag<void> {};
template <class... Ts>
using void_t = type_t<voider<Ts...>>;

namespace details {
template <template <class...> class Z, class, class... Ts>
struct can_apply : false_type {};
template <template <class...> class Z, class... Ts>
struct can_apply<Z, void_t<Z<Ts...>>, Ts...> : true_type {};
}  // namespace details
template <template <class...> class Z, class... Ts>
using can_apply = details::can_apply<Z, void, Ts...>;

namespace details {
template <class From, class To>
using try_convert = decltype(To{declval<From>()});
}
template <class From, class To>
struct is_convertible : can_apply<details::try_convert, From, To> {};
template <>
struct is_convertible<void, void> : true_type {};

// enable_if

template <bool, class = void>
struct enable_if {};
template <class T>
struct enable_if<true, T> : tag<T> {};
template <bool b, class T = void>
using enable_if_t = type_t<enable_if<b, T>>;

// res_of

namespace details {
template <class G, class... Args>
using invoke_t = decltype(declval<G>()(declval<Args>()...));

template <class Sig, class = void>
struct res_of {};
template <class G, class... Args>
struct res_of<G(Args...), void_t<invoke_t<G, Args...>>> : tag<invoke_t<G, Args...>> {};
}  // namespace details
template <class Sig>
using res_of = details::res_of<Sig>;
template <class Sig>
using res_of_t = type_t<res_of<Sig>>;

// aligned_storage

template <size_t size, size_t align>
struct alignas(align) aligned_storage_t {
    char buff[size];
};

// is_same

template <class A, class B>
struct is_same : false_type {};
template <class A>
struct is_same<A, A> : true_type {};

template <class Sig, size_t sz, size_t algn>
struct small_task;

template <class R, class... Args, size_t sz, size_t algn>
struct small_task<R(Args...), sz, algn> {
    struct vtable_t {
        void (*mover)(void* src, void* dest);
        void (*destroyer)(void*);
        R (*invoke)(void const* t, Args&&... args);
        template <class T>
        static vtable_t const* get() {
            static const vtable_t table = {
                [](void* src, void* dest) { new (dest) T(move(*static_cast<T*>(src))); },
                [](void* t) { static_cast<T*>(t)->~T(); },
                [](void const* t, Args&&... args) -> R { return (*static_cast<T const*>(t))(forward<Args>(args)...); }};
            return &table;
        }
    };
    vtable_t const* table = nullptr;
    aligned_storage_t<sz, algn> data;
    template <class F, class dF = decay_t<F>, enable_if_t<!is_same<dF, small_task>{}>* = nullptr,
              enable_if_t<is_convertible<res_of_t<dF&(Args...)>, R>{}>* = nullptr>
    small_task(F&& f) : table(vtable_t::template get<dF>()) {
        static_assert(sizeof(dF) <= sz, "object too large");
        static_assert(alignof(dF) <= algn, "object too aligned");
        new (&data) dF(forward<F>(f));
    }
    ~small_task() {
        if (table) table->destroyer(&data);
    }
    small_task(const small_task& o) : table(o.table) { data = o.data; }
    small_task(small_task&& o) : table(o.table) {
        if (table) table->mover(&o.data, &data);
    }
    small_task() {}
    small_task& operator=(const small_task& o) {
        this->~small_task();
        new (this) small_task(move(o));
        return *this;
    }
    small_task& operator=(small_task&& o) {
        this->~small_task();
        new (this) small_task(move(o));
        return *this;
    }
    explicit operator bool() const { return table; }
    R operator()(Args... args) const { return table->invoke(&data, forward<Args>(args)...); }
};

template <class R, class... Args, size_t sz, size_t algn>
inline bool operator==(const small_task<R(Args...), sz, algn>& __f, nullptr_t) {
    return !static_cast<bool>(__f);
}

/// @overload
template <class R, class... Args, size_t sz, size_t algn>
inline bool operator==(nullptr_t, const small_task<R(Args...), sz, algn>& __f) {
    return !static_cast<bool>(__f);
}

template <class R, class... Args, size_t sz, size_t algn>
inline bool operator!=(const small_task<R(Args...), sz, algn>& __f, nullptr_t) {
    return static_cast<bool>(__f);
}

/// @overload
template <class R, class... Args, size_t sz, size_t algn>
inline bool operator!=(nullptr_t, const small_task<R(Args...), sz, algn>& __f) {
    return static_cast<bool>(__f);
}

template <class Sig>
using function = small_task<Sig, sizeof(void*) * 4, alignof(void*)>;
}  // namespace nonstd

#endif /* _NONSTD_FUNCTIONAL_HHP */