non_propagating_cache.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2022, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2022, Knut Reinert & MPI für molekulare Genetik
// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
// -----------------------------------------------------------------------------------------------------
 
#pragma once
 
#include <optional>
 
#include <seqan3/core/platform.hpp>
 
namespace seqan3::detail
{
 
template <typename T>
    requires std::is_object_v<T>
class non_propagating_cache : public std::optional<T>
{
public:
    using std::optional<T>::optional;
    using std::optional<T>::operator=;
 
    constexpr non_propagating_cache(non_propagating_cache const &) noexcept
    {}
 
    constexpr non_propagating_cache(non_propagating_cache && other) noexcept
    {
        other.reset();
    }
 
    constexpr non_propagating_cache & operator=(non_propagating_cache const & other) noexcept
    {
        if (std::addressof(other) != this)
            this->reset();
        return *this;
    }
 
    constexpr non_propagating_cache & operator=(non_propagating_cache && other) noexcept
    {
        this->reset();
        other.reset();
        return *this;
    }
 
    template <class I>
    constexpr T & emplace_deref(I const & i)
        requires requires (I const & i) { T(*i); }
    {
        this->reset();
        this->emplace(*i);
        return this->value();
    }
};
 
} // namespace seqan3::detail