persist.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2019, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2019, 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 <range/v3/algorithm/copy.hpp>

#include <seqan3/core/type_traits/iterator.hpp>
#include <seqan3/core/type_traits/range.hpp>
#include <seqan3/core/type_traits/transformation_trait_or.hpp>
#include <seqan3/io/exception.hpp>
#include <seqan3/range/concept.hpp>
#include <seqan3/range/shortcuts.hpp>
#include <seqan3/range/container/concept.hpp>
#include <seqan3/range/view/detail.hpp>
#include <seqan3/std/algorithm>
#include <seqan3/std/concepts>
#include <seqan3/std/ranges>

namespace seqan3::detail
{

// ============================================================================
//  view_persist
// ============================================================================

template <std::ranges::InputRange urng_t>
class view_persist : public ranges::view_interface<view_persist<urng_t>>
{
private:
    std::shared_ptr<urng_t> urange;

public:
    using reference         = reference_t<urng_t>;
    using const_reference   = reference;
    using value_type        = value_type_t<urng_t>;
    using size_type         = detail::transformation_trait_or_t<seqan3::size_type<urng_t>, void>;
    using difference_type   = difference_type_t<urng_t>;
    using iterator          = std::ranges::iterator_t<urng_t>;
    using const_iterator    = iterator;

    view_persist()                                               noexcept = default; 
    constexpr view_persist(view_persist const & rhs)             noexcept = default; 
    constexpr view_persist(view_persist && rhs)                  noexcept = default; 
    constexpr view_persist & operator=(view_persist const & rhs) noexcept = default; 
    constexpr view_persist & operator=(view_persist && rhs)      noexcept = default; 
    ~view_persist()                                              noexcept = default; 

    view_persist(urng_t && _urange) :
        urange{new urng_t{std::move(_urange)}}
    {}

    const_iterator begin() const noexcept
    {
        return seqan3::begin(*urange);
    }

    const_iterator cbegin() const noexcept
    {
        return begin();
    }

    auto end() const noexcept
    {
        return seqan3::end(*urange);
    }

    auto cend() const noexcept
    {
        return end();
    }
};

template <typename urng_t>
view_persist(urng_t &&) -> view_persist<std::remove_reference_t<urng_t>>;

// ============================================================================
//  persist_fn (adaptor definition)
// ============================================================================


class persist_fn : public adaptor_base<persist_fn>
{
private:
    using base_t = adaptor_base<persist_fn>;

public:
    using base_t::base_t;

private:
    friend base_t;

    template <std::ranges::ViewableRange urng_t>
    static auto impl(urng_t && urange)
    {
        return std::view::all(std::forward<urng_t>(urange));
    }

    template <std::ranges::Range urng_t>
    static auto impl(urng_t && urange)
    {
        static_assert(!std::is_lvalue_reference_v<urng_t>, "BUG: lvalue-reference in persist_fn::impl().");
        return view_persist{std::move(urange)};
    }
};

} // namespace seqan3::detail

// ============================================================================
//  view::persist (adaptor instance definition)
// ============================================================================

namespace seqan3::view
{

inline auto constexpr persist = detail::persist_fn{};


} // namespace seqan3::view