value.hpp

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// Copyright 2009-present MongoDB, Inc.
//
// 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 the License.
 
#pragma once
 
#include <bsoncxx/v1/document/value-fwd.hpp> // IWYU pragma: export
 
//
 
#include <bsoncxx/v1/detail/prelude.hpp>
 
#include <bsoncxx/v1/config/export.hpp>
#include <bsoncxx/v1/detail/type_traits.hpp>
#include <bsoncxx/v1/document/view.hpp> // IWYU pragma: export
#include <bsoncxx/v1/element/view.hpp>  // IWYU pragma: export
#include <bsoncxx/v1/stdx/string_view.hpp>
 
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <functional>
#include <memory>
#include <type_traits>
#include <utility>
 
namespace bsoncxx {
namespace v1 {
namespace document {

class value {
   public:
    using deleter_type = std::function<void BSONCXX_ABI_CDECL(std::uint8_t*)>;

    using default_deleter_type = std::default_delete<std::uint8_t[]>;

    using noop_deleter_type = void(BSONCXX_ABI_CDECL*)(std::uint8_t*);

    static BSONCXX_ABI_EXPORT_CDECL(void) noop_deleter(std::uint8_t*);

    using unique_ptr_type = std::unique_ptr<std::uint8_t[], deleter_type>;
 
   private:
    unique_ptr_type _data;
 
    template <typename T>
    using is_value = detail::is_alike<T, value>;
 
    template <typename T>
    using to_bson_expr = decltype(to_bson(std::declval<T const&>(), std::declval<value&>()));
 
    template <typename T>
    struct has_to_bson : detail::conjunction<detail::negation<is_value<T>>, detail::is_detected<to_bson_expr, T>> {};
 
    template <typename T>
    using from_bson_expr = decltype(from_bson(std::declval<T&>(), std::declval<v1::document::view>()));
 
    template <typename T>
    struct has_from_bson : detail::conjunction<detail::negation<is_value<T>>, detail::is_detected<from_bson_expr, T>> {
    };
 
    template <typename T>
    struct is_valid_deleter
        : detail::disjunction<
              // std::function<T> may not be nothrow move constructible across all pre-C++20 implementations.
              // Deliberately allow an exemption that assumes it is de facto nothrow move constructible.
              std::is_same<T, deleter_type>,
              // Same requirements for D in std::unique_ptr<T, D> but without (nothrow) move assignability which is not
              // required for T in std::function<T>.
              detail::conjunction<
                  std::is_convertible<T, deleter_type>,
                  std::is_nothrow_destructible<T>,
                  std::is_nothrow_move_constructible<T>>> {};
 
   public:
    using const_iterator = v1::document::view::const_iterator;

    using iterator = const_iterator;

    ~value() = default;

    value(value&& other) noexcept = default;

    value& operator=(value&& other) noexcept = default;

    value(value const& other) : value{other.view()} {}

    value& operator=(value const& other) {
        *this = value{other.view()};
        return *this;
    }

    value() : _data{const_cast<std::uint8_t*>(v1::document::view{}.data()), &noop_deleter} {}

    template <typename Deleter, detail::enable_if_t<is_valid_deleter<Deleter>::value>* = nullptr>
    value(std::uint8_t* data, Deleter deleter) : _data{data, std::move(deleter)} {}

    template <typename Deleter, detail::enable_if_t<is_valid_deleter<Deleter>::value>* = nullptr>
    value(std::uint8_t* data, std::size_t length, Deleter deleter) : value{data, std::move(deleter)} {
        (void)v1::document::view{data, length}; // May throw.
    }

    explicit value(std::uint8_t* data) : value{data, default_deleter_type{}} {}

    explicit value(std::uint8_t* data, std::size_t length) : value{data} {
        (void)v1::document::view{data, length}; // May throw.
    }

    explicit value(unique_ptr_type ptr) : _data{std::move(ptr)} {}

    explicit value(unique_ptr_type ptr, std::size_t length) : value{std::move(ptr)} {
        (void)v1::document::view{_data.get(), length}; // May throw.
    }

    explicit value(v1::document::view view) {
        if (!view) {
            return;
        }
 
        v1::document::view const empty;
 
        if (view.data() == empty.data()) {
            _data = unique_ptr_type{const_cast<std::uint8_t*>(empty.data()), &noop_deleter};
        } else {
            _data = unique_ptr_type{new std::uint8_t[view.size()], default_deleter_type{}};
            std::memcpy(_data.get(), view.data(), view.size());
        }
    }

    template <typename T, detail::enable_if_t<has_to_bson<T>::value>* = nullptr>
    explicit value(T const& v) : value{} {
        to_bson(v, *this); // ADL.
    }

    value& operator=(v1::document::view view) {
        this->reset(view);
        return *this;
    }

    template <typename T, detail::enable_if_t<has_to_bson<T>::value>* = nullptr>
    value& operator=(T const& v) {
        *this = value{v};
        return *this;
    }

    template <typename T, detail::enable_if_t<has_from_bson<T>::value>* = nullptr>
    void get(T& v) const {
        from_bson(v, this->view()); // ADL.
    }

    template <
        typename T,
        detail::enable_if_t<detail::conjunction<std::is_default_constructible<T>, has_from_bson<T>>::value>* = nullptr>
    T get() const {
        T res;
        this->get(res);
        return res;
    }

    deleter_type const& get_deleter() const {
        return _data.get_deleter();
    }

    unique_ptr_type release() {
        return std::move(_data);
    }

    void reset(value v) {
        *this = std::move(v);
    }

    void reset(v1::document::view v) {
        *this = value{v};
    }

    v1::document::view view() const {
        return v1::document::view{_data.get()};
    }

    /* explicit(false) */ operator v1::document::view() const {
        return this->view();
    }

    const_iterator cbegin() const {
        return this->view().cbegin();
    }

    const_iterator cend() const {
        return this->view().cend();
    }

    const_iterator begin() const {
        return this->view().begin();
    }

    const_iterator end() const {
        return this->view().end();
    }

    const_iterator find(v1::stdx::string_view key) const {
        return this->view().find(key);
    }

    v1::element::view operator[](v1::stdx::string_view key) const {
        return this->view()[key];
    }

    std::uint8_t const* data() const {
        return _data.get();
    }

    std::size_t size() const {
        return this->view().size();
    }

    std::size_t length() const {
        return this->view().length();
    }

    bool empty() const {
        return this->view().empty();
    }

    explicit operator bool() const {
        return this->view().operator bool();
    }

    friend bool operator==(value const& lhs, value const& rhs) {
        return lhs.view() == rhs.view();
    }

    friend bool operator!=(value const& lhs, value const& rhs) {
        return !(lhs == rhs);
    }
};
 
} // namespace document
} // namespace v1
} // namespace bsoncxx
 
#include <bsoncxx/v1/detail/postlude.hpp>