integral_types.hpp

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#pragma once
 
/// @file userver/storages/postgres/io/integral_types.hpp
/// @brief Integral types I/O support
/// @ingroup userver_postgres_parse_and_format
 
#include <boost/endian/conversion.hpp>
 
#include <type_traits>
 
#include <userver/storages/postgres/exceptions.hpp>
#include <userver/storages/postgres/io/buffer_io_base.hpp>
#include <userver/storages/postgres/io/traits.hpp>
#include <userver/storages/postgres/io/type_mapping.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres::io {
 
namespace detail {
 
template <std::size_t Size>
struct IntegralType;
 
template <>
struct IntegralType<2> {
    using type = Smallint;
};
 
template <>
struct IntegralType<4> {
    using type = Integer;
};
 
template <>
struct IntegralType<8> {
    using type = Bigint;
};
 
template <std::size_t Size>
struct IntegralBySizeParser {
    using IntType = typename IntegralType<Size>::type;
    constexpr static std::size_t size = Size;
 
    static IntType ParseBuffer(const FieldBuffer& buf) {
        IntType i;
        std::memcpy(&i, buf.buffer, size);
        return boost::endian::big_to_native(i);
    }
};
 
template <typename T>
struct IntegralBinaryParser : BufferParserBase<T> {
    using BaseType = BufferParserBase<T>;
    using BaseType::BaseType;
 
    void operator()(const FieldBuffer& buf) {
        switch (buf.length) {
            case 2:
                this->value = IntegralBySizeParser<2>::ParseBuffer(buf);
                break;
            case 4:
                this->value = IntegralBySizeParser<4>::ParseBuffer(buf);
                break;
            case 8:
                this->value = IntegralBySizeParser<8>::ParseBuffer(buf);
                break;
            default:
                throw InvalidInputBufferSize{fmt::format(
                    "Invalid buffer size {} "
                    "for an integral value type (expecting size 2, 4, or 8). Not an "
                    "integer was returned from query.",
                    buf.length
                )};
        }
    }
};
 
template <typename T>
struct IntegralBinaryFormatter {
    static constexpr std::size_t size = sizeof(T);
    using BySizeType = typename IntegralType<size>::type;
 
    T value;
 
    explicit IntegralBinaryFormatter(T val) : value{val} {}
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        buf.reserve(buf.size() + size);
        auto tmp = boost::endian::native_to_big(static_cast<BySizeType>(value));
        const char* p = reinterpret_cast<char const*>(&tmp);
        const char* e = p + size;
        std::copy(p, e, std::back_inserter(buf));
    }
 
    /// Write the value to char buffer, the buffer MUST be already resized
    template <typename Iterator>
    void operator()(Iterator buffer) const {
        auto tmp = boost::endian::native_to_big(static_cast<BySizeType>(value));
        const char* p = reinterpret_cast<char const*>(&tmp);
        const char* e = p + size;
        std::copy(p, e, buffer);
    }
};
 
#if defined(__x86_64__) || defined(__aarch64__)
// 64bit architectures have two types for 64bit integers, this is the second one
using AltInteger = std::conditional_t<std::is_same_v<Bigint, long>, long long, long>;
static_assert(sizeof(AltInteger) == sizeof(Bigint));
#else
// 32bit architectures have two types for 32bit integers, this is the second one
using AltInteger = std::conditional_t<std::is_same_v<Integer, int>, long int, int>;
static_assert(sizeof(AltInteger) == sizeof(Integer));
#endif
 
}  // namespace detail
 
//@{
/** @name 2 byte integer */
template <>
struct BufferParser<Smallint> : detail::IntegralBinaryParser<Smallint> {
    explicit BufferParser(Smallint& val) : IntegralBinaryParser(val) {}
};
 
template <>
struct BufferFormatter<Smallint> : detail::IntegralBinaryFormatter<Smallint> {
    explicit BufferFormatter(Smallint val) : IntegralBinaryFormatter(val) {}
};
//@}
 
//@{
/** @name 4 byte integer */
template <>
struct BufferParser<Integer> : detail::IntegralBinaryParser<Integer> {
    explicit BufferParser(Integer& val) : IntegralBinaryParser(val) {}
};
 
template <>
struct BufferFormatter<Integer> : detail::IntegralBinaryFormatter<Integer> {
    explicit BufferFormatter(Integer val) : IntegralBinaryFormatter(val) {}
};
//@}
 
//@{
/** @name 8 byte integer */
template <>
struct BufferParser<Bigint> : detail::IntegralBinaryParser<Bigint> {
    explicit BufferParser(Bigint& val) : IntegralBinaryParser(val) {}
};
 
template <>
struct BufferFormatter<Bigint> : detail::IntegralBinaryFormatter<Bigint> {
    explicit BufferFormatter(Bigint val) : IntegralBinaryFormatter(val) {}
};
 
/// @cond
template <>
struct BufferParser<detail::AltInteger> : detail::IntegralBinaryParser<detail::AltInteger> {
    explicit BufferParser(detail::AltInteger& val) : IntegralBinaryParser(val) {}
};
 
template <>
struct BufferFormatter<detail::AltInteger> : detail::IntegralBinaryFormatter<detail::AltInteger> {
    explicit BufferFormatter(detail::AltInteger val) : IntegralBinaryFormatter(val) {}
};
/// @endcond
 
//@}
 
//@{
/** @name boolean */
template <>
struct BufferParser<bool> {
    bool& value;
    explicit BufferParser(bool& val) : value{val} {}
    void operator()(const FieldBuffer& buf);
};
 
template <>
struct BufferFormatter<bool> {
    bool value;
    explicit BufferFormatter(bool val) : value(val) {}
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        buf.push_back(value ? 1 : 0);
    }
};
//@}
 
//@{
/** @name C++ to PostgreSQL mapping for integral types */
template <>
struct CppToSystemPg<Smallint> : PredefinedOid<PredefinedOids::kInt2> {};
template <>
struct CppToSystemPg<Integer> : PredefinedOid<PredefinedOids::kInt4> {};
template <>
struct CppToSystemPg<Bigint> : PredefinedOid<PredefinedOids::kInt8> {};
template <>
struct CppToSystemPg<bool> : PredefinedOid<PredefinedOids::kBoolean> {};
 
/// @cond
template <>
struct CppToSystemPg<detail::AltInteger>
    : PredefinedOid<sizeof(detail::AltInteger) == 8 ? PredefinedOids::kInt8 : PredefinedOids::kInt4> {};
/// @endcond
 
//@}
 
}  // namespace storages::postgres::io
 
USERVER_NAMESPACE_END