common_containers.hpp

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#pragma once
 
/// @file userver/dump/common_containers.hpp
/// @brief Dump support for C++ Standard Library and Boost containers,
/// `std::optional`, utils::StrongTypedef, `std::{unique,shared}_ptr`
///
/// @note There are no traits in `CachingComponentBase`. If `T`
/// is writable/readable, we have to generate the code for dumps
/// regardless of `dump: enabled`. So it's important that all Read-Write
/// operations for containers are SFINAE-correct.
///
/// @ingroup userver_dump_read_write
 
#include <cstddef>
#include <memory>
#include <optional>
#include <type_traits>
#include <typeinfo>
#include <utility>
#include <variant>
 
#include <userver/utils/constexpr_indices.hpp>
#include <userver/utils/lazy_prvalue.hpp>
#include <userver/utils/meta.hpp>
#include <userver/utils/strong_typedef.hpp>
 
#include <userver/dump/common.hpp>
#include <userver/dump/meta.hpp>
#include <userver/dump/meta_containers.hpp>
#include <userver/dump/operations.hpp>
 
/// @cond
namespace boost {
 
namespace bimaps {
 
template <typename L, typename R, typename AP1, typename AP2, typename AP3>
class bimap;
 
}  // namespace bimaps
 
namespace multi_index {
 
template <typename Value, typename IndexSpecifierList, typename Allocator>
class multi_index_container;
 
}  // namespace multi_index
 
using bimaps::bimap;
using multi_index::multi_index_container;
 
}  // namespace boost
/// @endcond
 
USERVER_NAMESPACE_BEGIN
 
namespace dump {
 
namespace impl {
 
template <typename L, typename R, typename... Args>
using BoostBimap = boost::bimap<L, R, Args...>;
 
template <typename L, typename R, typename... Args>
using BoostBimapLeftKey = typename BoostBimap<L, R, Args...>::left_key_type;
 
template <typename L, typename R, typename... Args>
using BoostBimapRightKey = typename BoostBimap<L, R, Args...>::right_key_type;
 
template <typename T>
auto ReadLazyPrvalue(Reader& reader) {
    return utils::LazyPrvalue([&reader] { return reader.Read<T>(); });
}
 
[[noreturn]] void ThrowInvalidVariantIndex(const std::type_info& type, std::size_t index);
 
template <typename VariantType>
VariantType ReadVariant(Reader& reader, std::size_t index) {
    static constexpr auto kVariantSize = std::variant_size_v<VariantType>;
    std::optional<VariantType> result;
 
    utils::WithConstexprIndex<kVariantSize>(index, [&](auto index_constant) {
        static constexpr auto kIndex = decltype(index_constant)::value;
        using Alternative = std::variant_alternative_t<kIndex, VariantType>;
        // Not using ReadLazyPrvalue because of stdlib issues on some compilers.
        result.emplace(std::in_place_index<kIndex>, reader.Read<Alternative>());
    });
 
    return std::move(*result);
}
 
}  // namespace impl
 
/// @brief Container serialization support
template <typename T>
std::enable_if_t<kIsContainer<T> && kIsWritable<meta::RangeValueType<T>>> Write(Writer& writer, const T& value) {
    writer.Write(std::size(value));
    for (const auto& item : value) {
        // explicit cast for vector<bool> shenanigans
        writer.Write(static_cast<const meta::RangeValueType<T>&>(item));
    }
}
 
/// @brief Container deserialization support
template <typename T>
std::enable_if_t<kIsContainer<T> && kIsReadable<meta::RangeValueType<T>>, T> Read(Reader& reader, To<T>) {
    const auto size = reader.Read<std::size_t>();
    T result{};
    if constexpr (meta::kIsReservable<T>) {
        result.reserve(size);
    }
    for (std::size_t i = 0; i < size; ++i) {
        dump::Insert(result, reader.Read<meta::RangeValueType<T>>());
    }
    return result;
}
 
/// @brief Pair serialization support (for maps)
template <typename T, typename U>
std::enable_if_t<kIsWritable<T> && kIsWritable<U>, void> Write(Writer& writer, const std::pair<T, U>& value) {
    writer.Write(value.first);
    writer.Write(value.second);
}
 
/// @brief Pair deserialization support (for maps)
template <typename T, typename U>
std::enable_if_t<kIsReadable<T> && kIsReadable<U>, std::pair<T, U>> Read(Reader& reader, To<std::pair<T, U>>) {
    return {reader.Read<T>(), reader.Read<U>()};
}
 
/// @brief `std::optional` serialization support
template <typename T>
std::enable_if_t<kIsWritable<T>> Write(Writer& writer, const std::optional<T>& value) {
    writer.Write(value.has_value());
    if (value) {
        writer.Write(*value);
    }
}
 
/// @brief `std::optional` deserialization support
template <typename T>
std::enable_if_t<kIsReadable<T>, std::optional<T>> Read(Reader& reader, To<std::optional<T>>) {
    if (!reader.Read<bool>()) {
        return std::nullopt;
    }
    return impl::ReadLazyPrvalue<T>(reader);
}
 
/// @brief `std::variant` serialization support
template <typename... Args>
std::enable_if_t<(true && ... && kIsWritable<Args>)> Write(Writer& writer, const std::variant<Args...>& value) {
    writer.Write(value.index());
    std::visit([&writer](const auto& inner) { writer.Write(inner); }, value);
}
 
/// @brief `std::variant` deserialization support
template <typename... Args>
std::enable_if_t<(true && ... && (std::is_move_constructible_v<Args> && kIsReadable<Args>)), std::variant<Args...>>
Read(Reader& reader, To<std::variant<Args...>>) {
    const auto index = reader.Read<std::size_t>();
    if (index >= sizeof...(Args)) {
        impl::ThrowInvalidVariantIndex(typeid(std::variant<Args...>), index);
    }
    return impl::ReadVariant<std::variant<Args...>>(reader, index);
}
 
/// Allows reading `const T`, which is usually encountered as a member of some
/// container
template <typename T>
std::enable_if_t<kIsReadable<T>, T> Read(Reader& reader, To<const T>) {
    return Read(reader, To<T>{});
}
 
/// @brief utils::StrongTypedef serialization support
template <typename Tag, typename T, utils::StrongTypedefOps Ops>
std::enable_if_t<kIsWritable<T>> Write(Writer& writer, const utils::StrongTypedef<Tag, T, Ops>& object) {
    writer.Write(object.GetUnderlying());
}
 
/// @brief utils::StrongTypedef deserialization support
template <typename Tag, typename T, utils::StrongTypedefOps Ops>
std::enable_if_t<kIsReadable<T>, utils::StrongTypedef<Tag, T, Ops>>
Read(Reader& reader, To<utils::StrongTypedef<Tag, T, Ops>>) {
    return utils::StrongTypedef<Tag, T, Ops>{reader.Read<T>()};
}
 
/// @brief `std::unique_ptr` serialization support
template <typename T>
std::enable_if_t<kIsWritable<T>> Write(Writer& writer, const std::unique_ptr<T>& ptr) {
    writer.Write(static_cast<bool>(ptr));
    if (ptr) {
        writer.Write(*ptr);
    }
}
 
/// @brief `std::unique_ptr` deserialization support
template <typename T>
std::enable_if_t<kIsReadable<T>, std::unique_ptr<T>> Read(Reader& reader, To<std::unique_ptr<T>>) {
    if (!reader.Read<bool>()) {
        return {};
    }
    return std::make_unique<T>(impl::ReadLazyPrvalue<T>(reader));
}
 
/// @brief `std::shared_ptr` serialization support
/// @warning If two or more `shared_ptr` within a single dumped entity point to
/// the same object, they will point to its distinct copies after loading a dump
template <typename T>
std::enable_if_t<kIsWritable<T>> Write(Writer& writer, const std::shared_ptr<T>& ptr) {
    writer.Write(static_cast<bool>(ptr));
    if (ptr) {
        writer.Write(*ptr);
    }
}
 
/// @brief `std::shared_ptr` deserialization support
/// @warning If two or more `shared_ptr` within a single dumped entity point to
/// the same object, they will point to its distinct copies after loading a dump
template <typename T>
std::enable_if_t<kIsReadable<T>, std::shared_ptr<T>> Read(Reader& reader, To<std::shared_ptr<T>>) {
    if (!reader.Read<bool>()) {
        return {};
    }
    return std::make_shared<T>(impl::ReadLazyPrvalue<T>(reader));
}
 
/// @brief `boost::bimap` serialization support
template <typename L, typename R, typename... Args>
std::enable_if_t<
    kIsWritable<impl::BoostBimapLeftKey<L, R, Args...>> && kIsWritable<impl::BoostBimapRightKey<L, R, Args...>>>
Write(Writer& writer, const boost::bimap<L, R, Args...>& map) {
    writer.Write(map.size());
 
    for (const auto& [left, right] : map) {
        writer.Write(left);
        writer.Write(right);
    }
}
 
/// @brief `boost::bimap` deserialization support
template <typename L, typename R, typename... Args>
std::enable_if_t<
    kIsReadable<impl::BoostBimapLeftKey<L, R, Args...>> && kIsReadable<impl::BoostBimapRightKey<L, R, Args...>>,
    boost::bimap<L, R, Args...>>
Read(Reader& reader, To<boost::bimap<L, R, Args...>>) {
    using BoostBimap = impl::BoostBimap<L, R, Args...>;
 
    using BoostBimapLeftKey = impl::BoostBimapLeftKey<L, R, Args...>;
    using BoostBimapRightKey = impl::BoostBimapRightKey<L, R, Args...>;
 
    using BoostBimapSizeType = typename BoostBimap::size_type;
 
    BoostBimap map;
    // bimap doesn't have reserve :(
 
    const auto size = reader.Read<BoostBimapSizeType>();
    for (BoostBimapSizeType i = 0; i < size; ++i) {
        // `Read`s are guaranteed to occur left-to-right in brace-init
        map.insert({
            reader.Read<BoostBimapLeftKey>(),
            reader.Read<BoostBimapRightKey>(),
        });
    }
 
    return map;
}
 
/// @brief `boost::multi_index_container` serialization support
template <typename T, typename Index, typename Alloc>
std::enable_if_t<kIsWritable<T>> Write(Writer& writer, const boost::multi_index_container<T, Index, Alloc>& container) {
    writer.Write(container.template get<0>().size());
    for (auto& item : container.template get<0>()) {
        writer.Write(item);
    }
}
 
/// @brief `boost::multi_index_container` deserialization support
template <typename T, typename Index, typename Alloc>
std::enable_if_t<kIsReadable<T>, boost::multi_index_container<T, Index, Alloc>>
Read(Reader& reader, To<boost::multi_index_container<T, Index, Alloc>>) {
    const auto size = reader.Read<std::size_t>();
    boost::multi_index_container<T, Index, Alloc> container;
 
    // boost::multi_index_container has reserve() with some, but not all, configs
    if constexpr (meta::kIsReservable<boost::multi_index_container<T, Index, Alloc>>) {
        container.reserve(size);
    }
 
    for (std::size_t i = 0; i < size; ++i) {
        container.insert(reader.Read<T>());
    }
 
    return container;
}
 
}  // namespace dump
 
USERVER_NAMESPACE_END