file_view.hpp

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// Copyright Take Vos 2019, 2021-2022.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)

 
#pragma once
 
#include "file_intf.hpp"
#if HI_OPERATING_SYSTEM == HI_OS_WINDOWS
#include "file_view_win32_impl.hpp"
#endif
#include "access_mode.hpp"
#include "../container/container.hpp"
#include "../char_maps/char_maps.hpp" // XXX #619
#include "../utility/utility.hpp"
#include "../macros.hpp"
#include <span>
#include <filesystem>
#include <memory>
 
hi_export_module(hikogui.file.file_view);
 
hi_warning_push();
// C26490: Don't use reinterpret_cast (type.1).
// We need to convert bytes to chars to get a string_view from the byte buffer.
hi_warning_ignore_msvc(26490);
 
hi_export namespace hi { inline namespace v1 {

class file_view {
public:
    ~file_view() = default;
    constexpr file_view() noexcept = default;
    file_view(file_view const& other) noexcept = default;
    file_view(file_view&& other) noexcept = default;
    file_view& operator=(file_view const& other) noexcept = default;
    file_view& operator=(file_view&& other) noexcept = default;

    file_view(file const& file, std::size_t offset = 0, std::size_t size = 0) :
        _pimpl(std::make_shared<detail::file_view_impl>(file.pimpl(), offset, size))
    {
    }
 
    file_view(
        std::filesystem::path const& path,
        access_mode access_mode = access_mode::open_for_read,
        std::size_t offset = 0,
        std::size_t size = 0) :
        file_view(file{path, access_mode}, offset, size)
    {
    }
 
    [[nodiscard]] std::size_t offset() const noexcept
    {
        hi_assert_not_null(_pimpl);
        return _pimpl->offset();
    }
 
    [[nodiscard]] std::size_t size() const noexcept
    {
        hi_assert_not_null(_pimpl);
        return _pimpl->size();
    }

    [[nodiscard]] bool unmapped() const noexcept
    {
        if (_pimpl) {
            if (_pimpl->unmapped()) {
                _pimpl = nullptr;
                return true;
            } else {
                return false;
            }
        } else {
            return true;
        }
    }

    explicit operator bool() const noexcept
    {
        return not unmapped();
    }
 
    void unmap() noexcept
    {
        if (auto pimpl = std::exchange(_pimpl, nullptr)) {
            pimpl->unmap();
        }
    }

    [[nodiscard]] void_span void_span() const noexcept
    {
        hi_assert_not_null(_pimpl);
        return _pimpl->void_span();
    }

    [[nodiscard]] const_void_span const_void_span() const noexcept
    {
        hi_assert_not_null(_pimpl);
        return _pimpl->const_void_span();
    }

    void flush(hi::void_span span) const noexcept
    {
        hi_assert_not_null(_pimpl);
        return _pimpl->flush(span);
    }
 
    template<typename T>
    [[nodiscard]] friend std::span<T> as_span(file_view const& view) noexcept
    {
        if constexpr (std::is_const_v<T>) {
            return as_span<T>(view.const_void_span());
        } else {
            return as_span<T>(view.void_span());
        }
    }
 
    [[nodiscard]] friend std::string_view as_string_view(file_view const& view) noexcept
    {
        hi_assert(view.offset() == 0);
        return as_string_view(view.const_void_span());
    }
 
    [[nodiscard]] friend bstring_view as_bstring_view(file_view const& view) noexcept
    {
        hi_assert(view.offset() == 0);
        return as_bstring_view(view.const_void_span());
    }
 
private:
    mutable std::shared_ptr<detail::file_view_impl> _pimpl;
};
 
}} // namespace hi::v1
 
hi_warning_pop();