common.hpp

Go to the documentation of this file.

#pragma once
 
/// @file userver/dump/common.hpp
/// @brief Serialization and deserialization of integral, floating point,
/// string, `std::chrono`, `enum` and `uuid` types for dumps.
///
/// @ingroup userver_dump_read_write
 
#include <chrono>
#include <cstdint>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
 
#include <userver/dump/operations.hpp>
#include <userver/dump/unsafe.hpp>
#include <userver/utils/meta_light.hpp>
#include <userver/utils/numeric_cast.hpp>
 
namespace boost::uuids {
struct uuid;
}
 
USERVER_NAMESPACE_BEGIN
 
namespace decimal64 {
template <int Prec, typename RoundPolicy>
class Decimal;
}  // namespace decimal64
 
namespace formats::json {
class Value;
}  // namespace formats::json
 
namespace dump {
 
/// @brief Reads the rest of the data from `reader`
std::string ReadEntire(Reader& reader);
 
namespace impl {
 
/// @brief Helpers for serialization of trivially-copyable types
template <typename T>
void WriteTrivial(Writer& writer, T value) {
    static_assert(std::is_trivially_copyable_v<T>);
    // TODO: endianness
    WriteStringViewUnsafe(writer, std::string_view{reinterpret_cast<const char*>(&value), sizeof(value)});
}
 
/// @brief Helpers for deserialization trivially-copyable types
template <typename T>
T ReadTrivial(Reader& reader) {
    static_assert(std::is_trivially_copyable_v<T>);
    T value{};
    // TODO: endianness
    ReadStringViewUnsafe(reader, sizeof(T)).copy(reinterpret_cast<char*>(&value), sizeof(T));
    return value;
}
 
void WriteInteger(Writer& writer, std::uint64_t value);
 
std::uint64_t ReadInteger(Reader& reader);
 
template <typename Duration>
inline constexpr bool kIsDumpedAsNanoseconds =
    std::is_integral_v<typename Duration::rep> && (Duration::period::num == 1) &&
    (Duration{1} <= std::chrono::milliseconds{1}) && (1'000'000'000 % Duration::period::den == 0);
 
}  // namespace impl
 
/// @brief Write-only `std::string_view` support
/// @see `ReadStringViewUnsafe`
void Write(Writer& writer, std::string_view value);
 
/// @brief `std::string` serialization support
void Write(Writer& writer, const std::string& value);
 
/// @brief `std::string` deserialization support
std::string Read(Reader& reader, To<std::string>);
 
/// @brief Allows writing string literals
void Write(Writer& writer, const char* value);
 
/// @brief Integral types serialization support
template <typename T>
std::enable_if_t<meta::kIsInteger<T>> Write(Writer& writer, T value) {
    if constexpr (sizeof(T) == 1) {
        impl::WriteTrivial(writer, value);
    } else {
        impl::WriteInteger(writer, static_cast<std::uint64_t>(value));
    }
}
 
/// @brief Integral types deserialization support
template <typename T>
std::enable_if_t<meta::kIsInteger<T>, T> Read(Reader& reader, To<T>) {
    if constexpr (sizeof(T) == 1) {
        return impl::ReadTrivial<T>(reader);
    }
 
    const auto raw = impl::ReadInteger(reader);
 
    if constexpr (std::is_signed_v<T>) {
        return utils::numeric_cast<T>(static_cast<std::int64_t>(raw));
    } else {
        return utils::numeric_cast<T>(raw);
    }
}
 
/// @brief Floating-point serialization support
template <typename T>
std::enable_if_t<std::is_floating_point_v<T>> Write(Writer& writer, T value) {
    impl::WriteTrivial(writer, value);
}
 
/// @brief Floating-point deserialization support
template <typename T>
std::enable_if_t<std::is_floating_point_v<T>, T> Read(Reader& reader, To<T>) {
    return impl::ReadTrivial<T>(reader);
}
 
/// @brief bool serialization support
void Write(Writer& writer, bool value);
 
/// @brief bool deserialization support
bool Read(Reader& reader, To<bool>);
 
/// @brief enum serialization support
template <typename T>
std::enable_if_t<std::is_enum_v<T>> Write(Writer& writer, T value) {
    writer.Write(static_cast<std::underlying_type_t<T>>(value));
}
 
/// @brief enum deserialization support
template <typename T>
std::enable_if_t<std::is_enum_v<T>, T> Read(Reader& reader, To<T>) {
    return static_cast<T>(reader.Read<std::underlying_type_t<T>>());
}
 
/// @brief `std::chrono::duration` serialization support
template <typename Rep, typename Period>
void Write(Writer& writer, std::chrono::duration<Rep, Period> value) {
    using std::chrono::duration, std::chrono::nanoseconds;
 
    // Durations, which on some systems represent
    // `std::chrono::*_clock::duration`, are serialized as `std::nanoseconds`
    // to avoid system dependency
    if constexpr (impl::kIsDumpedAsNanoseconds<duration<Rep, Period>>) {
        const auto count = std::chrono::duration_cast<nanoseconds>(value).count();
 
        if (nanoseconds{count} != value) {
            throw std::logic_error(
                "Trying to serialize a huge duration, it does not fit into "
                "std::chrono::nanoseconds type"
            );
        }
        impl::WriteTrivial(writer, count);
    } else {
        impl::WriteTrivial(writer, value.count());
    }
}
 
/// @brief `std::chrono::duration` deserialization support
template <typename Rep, typename Period>
std::chrono::duration<Rep, Period> Read(Reader& reader, To<std::chrono::duration<Rep, Period>>) {
    using std::chrono::duration, std::chrono::nanoseconds;
 
    if constexpr (impl::kIsDumpedAsNanoseconds<duration<Rep, Period>>) {
        const auto count = impl::ReadTrivial<nanoseconds::rep>(reader);
        return std::chrono::duration_cast<duration<Rep, Period>>(nanoseconds{count});
    } else {
        const auto count = impl::ReadTrivial<Rep>(reader);
        return duration<Rep, Period>{count};
    }
}
 
/// @brief `std::chrono::time_point` serialization support
/// @note Only `system_clock` is supported, because `steady_clock` can only
/// be used within a single execution
template <typename Duration>
void Write(Writer& writer, std::chrono::time_point<std::chrono::system_clock, Duration> value) {
    writer.Write(value.time_since_epoch());
}
 
/// @brief `std::chrono::time_point` deserialization support
/// @note Only `system_clock` is supported, because `steady_clock` can only
/// be used within a single execution
template <typename Duration>
auto Read(Reader& reader, To<std::chrono::time_point<std::chrono::system_clock, Duration>>) {
    return std::chrono::time_point<std::chrono::system_clock, Duration>{reader.Read<Duration>()};
}
 
/// @brief `boost::uuids::uuid` serialization support
void Write(Writer& writer, const boost::uuids::uuid& value);
 
/// @brief `boost::uuids::uuid` deserialization support
boost::uuids::uuid Read(Reader& reader, To<boost::uuids::uuid>);
 
/// @brief decimal64::Decimal serialization support
template <int Prec, typename RoundPolicy>
inline void Write(Writer& writer, const decimal64::Decimal<Prec, RoundPolicy>& dec) {
    writer.Write(dec.AsUnbiased());
}
 
/// @brief decimal64::Decimal deserialization support
template <int Prec, typename RoundPolicy>
auto Read(Reader& reader, dump::To<decimal64::Decimal<Prec, RoundPolicy>>) {
    return decimal64::Decimal<Prec, RoundPolicy>::FromUnbiased(reader.Read<int64_t>());
}
 
/// @brief formats::json::Value serialization support
void Write(Writer& writer, const formats::json::Value& value);
 
/// @brief formats::json::Value deserialization support
formats::json::Value Read(Reader& reader, To<formats::json::Value>);
 
}  // namespace dump
 
USERVER_NAMESPACE_END