mbed-os/platform/cxxsupport/mstd_functional

/* mbed Microcontroller Library
 * Copyright (c) 2019 ARM Limited
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under tUNChe License.
 */
#ifndef MSTD_FUNCTIONAL_
#define MSTD_FUNCTIONAL_

/* <mstd_functional>
 *
 * - includes toolchain's <functional>
 * - For ARM C 5, standard C++11/14 features:
 *   - std::mem_fn,
 *   - std::reference_wrapper, std::ref, std::cref
 *   - transparent std::plus<> etc
 *   - std::bit_and, std::bit_or, std::bit_xor, std::bit_not
 * - For all toolchains, C++17/20 backports:
 *   - mstd::not_fn (C++17)
 *   - mstd::invoke (C++17)
 *   - mstd::unwrap_reference, mstd::unwrap_ref_decay (C++20)
 */

#include <functional>

#include <mstd_memory> // addressof
#include <mstd_utility> // forward
#include <mstd_type_traits>

#ifdef __CC_ARM

namespace std
{
// [func.memfn]
namespace impl {
template <typename R, typename T>
class mem_fn_t {
    R T::* pm;
public:
    mem_fn_t(R T::* pm) : pm(pm) { }
    template <typename... Args>
    invoke_result_t<R T::*, Args...> operator()(Args&&... args) const
    {
        return std::invoke(pm, std::forward<Args>(args)...);
    }
};
}

template <class R, class T>
impl::mem_fn_t<R, T> mem_fn(R T::* pm)
{
    return impl::mem_fn_t<R, T>(pm);
}

} // namespace std

#endif // __CC_ARM

namespace mstd {

// [func.invoke]
#if __cpp_lib_invoke >= 201411
using std::invoke;
#else
template <typename F, typename... Args>
invoke_result_t<F, Args...> invoke(F&& f, Args&&... args)
{
    return impl::INVOKE(std::forward<F>(f), std::forward<Args>(args)...);
}
#endif // __cpp_lib_invoke

} // namespace mstd

#ifdef __CC_ARM
namespace std {

    using mstd::invoke;

// [refwrap]
template <typename T>
class reference_wrapper {
    T *ptr;
public:
    using type = T;
    // [refwrap.const]
    // LWG 2993 version of constructor does not seem to work in ARM C 5, so stick with
    // this original version.
    reference_wrapper(T &x) noexcept : ptr(addressof(x)) { }
    reference_wrapper(T &&x) = delete;

    reference_wrapper(const reference_wrapper &) noexcept = default;
    // [refwrap.assign]
    reference_wrapper &operator=(const reference_wrapper &) noexcept = default;

    // [refwrap.access]
    operator T &() const noexcept { return *ptr; }
    T &get() const noexcept { return *ptr; }

    // [refwrap.invoke]
    template <typename... ArgTypes>
    invoke_result_t<T &, ArgTypes...> operator()(ArgTypes&&... args) const
    {
        return std::invoke(get(), forward<ArgTypes>(args)...);
    }
};

// [refwrap.helpers]
template <typename T>
reference_wrapper<T> ref(T &t) noexcept
{
    return reference_wrapper<T>(t);
}

template <typename T>
reference_wrapper<T> ref(reference_wrapper<T> &t) noexcept
{
    return ref(t.get());
}

template <typename T>
void ref(const T &&) = delete;

template <typename T>
reference_wrapper<const T> cref(const T &t) noexcept
{
    return reference_wrapper<const T>(t);
}

template <typename T>
reference_wrapper<const T> cref(reference_wrapper<T> &t) noexcept
{
    return cref(t.get());
}

template <typename T>
void cref(const T &&) = delete;

// ARMC5 has basic plus<T> etc - we can add plus<void> specialisations;
// and the language rules allow us to add the default void arguments missing
// from its header.

template <typename T = void> struct plus;
template <typename T = void> struct minus;
template <typename T = void> struct multiplies;
template <typename T = void> struct divides;
template <typename T = void> struct modulus;
template <typename T = void> struct negate;
template <typename T = void> struct equal_to;
template <typename T = void> struct not_equal_to;
template <typename T = void> struct greater;
template <typename T = void> struct less;
template <typename T = void> struct greater_equal;
template <typename T = void> struct less_equal;
template <typename T = void> struct logical_and;
template <typename T = void> struct logical_or;
template <typename T = void> struct logical_not;

// [arithmetic.operations.plus]
template <>
struct plus<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) + std::forward<U>(u))
    {
        return std::forward<T>(t) + std::forward<U>(u);
    }
};

// [arithmetic.operations.minus]
template <>
struct minus<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) - std::forward<U>(u))
    {
        return std::forward<T>(t) - std::forward<U>(u);
    }
};

// [arithmetic.operations.multiplies]
template <>
struct multiplies<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) * std::forward<U>(u))
    {
        return std::forward<T>(t) * std::forward<U>(u);
    }
};

// [arithmetic.operations.divides]
template <>
struct divides<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) / std::forward<U>(u))
    {
        return std::forward<T>(t) / std::forward<U>(u);
    }
};

// [arithmetic.operations.modulus]
template <>
struct modulus<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) % std::forward<U>(u))
    {
        return std::forward<T>(t) % std::forward<U>(u);
    }
};

// [arithmetic.operations.negate]
template <>
struct negate<void> {
    using is_transparent = true_type;
    template <typename T>
    constexpr auto operator()(T&& t) const -> decltype(-std::forward<T>(t))
    {
        return -std::forward<T>(t);
    }
};

// [comparisons.equal_to]
template <>
struct equal_to<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) == std::forward<U>(u))
    {
        return std::forward<T>(t) == std::forward<U>(u);
    }
};

// [comparisons.not_equal_to]
template <>
struct not_equal_to<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) != std::forward<U>(u))
    {
        return std::forward<T>(t) != std::forward<U>(u);
    }
};

// [comparisons.greater]
template <>
struct greater<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) > std::forward<U>(u))
    {
        return std::forward<T>(t) > std::forward<U>(u);
    }
};

// [comparisons.less]
template <>
struct less<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) < std::forward<U>(u))
    {
        return std::forward<T>(t) < std::forward<U>(u);
    }
};

// [comparisons.greater_equal]
template <>
struct greater_equal<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) >= std::forward<U>(u))
    {
        return std::forward<T>(t) >= std::forward<U>(u);
    }
};

// [comparisons.less_equal]
template <>
struct less_equal<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) <= std::forward<U>(u))
    {
        return std::forward<T>(t) <= std::forward<U>(u);
    }
};

// [logical.operations.and]
template <>
struct logical_and<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) && std::forward<U>(u))
    {
        return std::forward<T>(t) && std::forward<U>(u);
    }
};

// [logical.operations.or]
template <>
struct logical_or<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) || std::forward<U>(u))
    {
        return std::forward<T>(t) || std::forward<U>(u);
    }
};

// [logical.operations.not]
template <>
struct logical_not<void> {
    using is_transparent = true_type;
    template <typename T>
    constexpr auto operator()(T&& t) const -> decltype(!std::forward<T>(t))
    {
        return !std::forward<T>(t);
    }
};

// [bitwise.operations.and]
template <typename T = void>
struct bit_and {
    constexpr T operator()(const T &x, const T &y) const
    {
        return x & y;
    }
};

template <>
struct bit_and<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t,U&& u) const -> decltype(std::forward<T>(t) & std::forward<U>(u))
    {
        return std::forward<T>(t) & std::forward<U>(u);
    }
};

// [bitwise.operations.or]
template <typename T = void>
struct bit_or {
    constexpr T operator()(const T &x, const T &y) const
    {
        return x & y;
    }
};

template <>
struct bit_or<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t,U&& u) const -> decltype(std::forward<T>(t) | std::forward<U>(u))
    {
        return std::forward<T>(t) | std::forward<U>(u);
    }
};

// [bitwise.operations.xor]
template <typename T = void>
struct bit_xor {
    constexpr T operator()(const T &x, const T &y) const
    {
        return x ^ y;
    }
};

template <>
struct bit_xor<void> {
    using is_transparent = true_type;
    template <typename T, typename U>
    constexpr auto operator()(T&& t,U&& u) const -> decltype(std::forward<T>(t) ^ std::forward<U>(u))
    {
        return std::forward<T>(t) ^ std::forward<U>(u);
    }
};

// [bitwise.operations.not]
template <typename T = void>
struct bit_not {
    constexpr T operator()(const T &arg) const
    {
        return ~arg;
    }
};

template <>
struct bit_not<void> {
    using is_transparent = true_type;
    template <typename T>
    constexpr auto operator()(T&& arg) const -> decltype(~std::forward<T>(arg))
    {
        return ~std::forward<T>(arg);
    }
};

} // namespace std

#endif // __CC_ARM

namespace mstd {
using std::reference_wrapper;
using std::ref;
using std::cref;
using std::plus;
using std::minus;
using std::multiplies;
using std::divides;
using std::modulus;
using std::negate;
using std::equal_to;
using std::not_equal_to;
using std::greater;
using std::less;
using std::greater_equal;
using std::less_equal;
using std::logical_and;
using std::logical_or;
using std::logical_not;
using std::bit_and;
using std::bit_or;
using std::bit_xor;
using std::bit_not;

#if __cpp_lib_not_fn >= 201603
using std::not_fn;
#else
namespace impl {
// [func.not_fn]
template <typename F>
class not_fn_t {
    std::decay_t<F> fn;
public:
    explicit not_fn_t(F&& f) : fn(std::forward<F>(f)) { }
    not_fn_t(const not_fn_t &other) = default;
    not_fn_t(not_fn_t &&other) = default;

    template<typename... Args>
    auto operator()(Args&&... args) & -> decltype(!std::declval<invoke_result_t<std::decay_t<F> &, Args...>>())
    {
        return !mstd::invoke(fn, std::forward<Args>(args)...);
    }

    template<typename... Args>
    auto operator()(Args&&... args) const & -> decltype(!std::declval<invoke_result_t<std::decay_t<F> const &, Args...>>())
    {
        return !mstd::invoke(fn, std::forward<Args>(args)...);
    }

    template<typename... Args>
    auto operator()(Args&&... args) && -> decltype(!std::declval<invoke_result_t<std::decay_t<F>, Args...>>())
    {
        return !mstd::invoke(std::move(fn), std::forward<Args>(args)...);
    }

    template<typename... Args>
    auto operator()(Args&&... args) const && -> decltype(!std::declval<invoke_result_t<std::decay_t<F> const, Args...>>())
    {
        return !mstd::invoke(std::move(fn), std::forward<Args>(args)...);
    }
};
}

template <typename F>
impl::not_fn_t<F> not_fn(F&& f)
{
    return impl::not_fn_t<F>(std::forward<F>(f));
}
#endif

/* C++20 unwrap_reference */
template <typename T>
struct unwrap_reference : type_identity<T> { };
template <typename T>
struct unwrap_reference<std::reference_wrapper<T>> : type_identity<T &> { };
template <typename T>
using unwrap_reference_t = typename unwrap_reference<T>::type;

/* C++20 unwrap_ref_decay */
template <typename T>
struct unwrap_ref_decay : unwrap_reference<std::decay_t<T>> { };
template <typename T>
using unwrap_ref_decay_t = typename unwrap_ref_decay<T>::type;

}

#endif // MSTD_FUNCTIONAL_