field_buffer.hpp

#pragma once
 
#include <userver/storages/postgres/exceptions.hpp>
#include <userver/storages/postgres/io/buffer_io.hpp>
#include <userver/storages/postgres/io/integral_types.hpp>
#include <userver/storages/postgres/io/nullable_traits.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres::io {
 
inline constexpr FieldBuffer FieldBuffer::GetSubBuffer(std::size_t offset, std::size_t size, BufferCategory cat) const {
    const auto* new_buffer_start = buffer + offset;
    if (offset > length) {
        throw InvalidInputBufferSize(fmt::format("Offset {} requested for a buffer of size {}", offset, length));
    }
    size = size == npos ? length - offset : size;
    if (offset + size > length) {
        throw InvalidInputBufferSize(
            fmt::format("Attempt to read {} bytes more than was sent by server", offset + size - length)
        );
    }
    if (cat == BufferCategory::kKeepCategory) {
        cat = category;
    }
    return {is_null, cat, size, new_buffer_start};
}
 
template <typename T>
std::size_t FieldBuffer::Read(T&& value, BufferCategory cat, std::size_t len) {
    io::ReadBuffer(GetSubBuffer(0, len, cat), std::forward<T>(value));
    length -= len;
    buffer += len;
    return len;
}
 
template <typename T>
std::size_t FieldBuffer::Read(T&& value, const TypeBufferCategory& categories, std::size_t len, BufferCategory cat) {
    io::ReadBuffer(GetSubBuffer(0, len, cat), std::forward<T>(value), categories);
    length -= len;
    buffer += len;
    return len;
}
 
template <typename T>
std::size_t FieldBuffer::ReadRaw(T&& value, const TypeBufferCategory& categories, BufferCategory cat) {
    using ValueType = std::decay_t<T>;
    Integer field_length{0};
    auto consumed = Read(field_length, BufferCategory::kPlainBuffer);
    if (field_length == kPgNullBufferSize) {
        // NULL value
        traits::GetSetNull<ValueType>::SetNull(std::forward<T>(value));
        return consumed;
    } else if (field_length < 0) {
        // invalid length value
        throw InvalidInputBufferSize(fmt::format("Negative buffer size value {}", field_length));
    } else if (field_length == 0) {
        traits::GetSetNull<ValueType>::SetDefault(std::forward<T>(value));
        return consumed;
    } else {
        return consumed + Read(value, categories, field_length, cat);
    }
}
 
template <typename T>
std::size_t ReadRawBinary(FieldBuffer buffer, T& value, const TypeBufferCategory& categories) {
    return buffer.ReadRaw(value, categories);
}
 
namespace detail {
 
template <typename T, typename Buffer, typename Enable = USERVER_NAMESPACE::utils::void_t<>>
struct FormatterAcceptsReplacementOid : std::false_type {};
 
template <typename T, typename Buffer>
struct FormatterAcceptsReplacementOid<
    T,
    Buffer,
    USERVER_NAMESPACE::utils::void_t<
        decltype(std::declval<T&>()(std::declval<const UserTypes&>(), std::declval<Buffer&>(), std::declval<Oid>()))>>
    : std::true_type {};
 
}  // namespace detail
 
template <typename T, typename Buffer>
void WriteRawBinary(
    const UserTypes& types,
    Buffer& buffer,
    const T& value,
    [[maybe_unused]] Oid replace_oid = kInvalidOid
) {
    traits::CheckFormatter<T>();
    static constexpr auto size_len = sizeof(Integer);
    if (traits::GetSetNull<T>::IsNull(value)) {
        io::WriteBuffer(types, buffer, kPgNullBufferSize);
    } else {
        using BufferFormatter = typename traits::IO<T>::FormatterType;
        using AcceptsReplacementOid = detail::FormatterAcceptsReplacementOid<BufferFormatter, Buffer>;
        auto len_start = buffer.size();
        buffer.resize(buffer.size() + size_len);
        auto size_before = buffer.size();
        if constexpr (AcceptsReplacementOid{}) {
            BufferFormatter{value}(types, buffer, replace_oid);
        } else {
            io::WriteBuffer(types, buffer, value);
        }
        const Integer bytes = buffer.size() - size_before;
        BufferWriter(bytes)(buffer.begin() + len_start);
    }
}
 
}  // namespace storages::postgres::io
 
USERVER_NAMESPACE_END