boost_multiprecision.hpp

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#pragma once
 
/// @file userver/storages/postgres/io/boost_multiprecision.hpp
/// @brief boost::multiprecision I/O support
/// @ingroup userver_postgres_parse_and_format
 
#include <userver/storages/postgres/io/buffer_io.hpp>
#include <userver/storages/postgres/io/buffer_io_base.hpp>
#include <userver/storages/postgres/io/numeric_data.hpp>
#include <userver/storages/postgres/io/type_mapping.hpp>
 
#include <boost/multiprecision/cpp_dec_float.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres {
 
template <unsigned Precision = 50>
using MultiPrecision = boost::multiprecision::number<boost::multiprecision::cpp_dec_float<Precision>>;
 
namespace io {
 
template <unsigned Precision>
struct BufferFormatter<MultiPrecision<Precision>> {
    using Value = MultiPrecision<Precision>;
    const Value& value;
 
    BufferFormatter(const Value& val)
        : value{val}
    {}
 
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        auto str_rep = value.str(std::numeric_limits<Value>::max_digits10, std::ios_base::fixed);
        auto bin_str = detail::StringToNumericBuffer(str_rep);
        buf.reserve(buf.size() + bin_str.size());
        std::copy(bin_str.begin(), bin_str.end(), std::back_inserter(buf));
    }
};
 
template <unsigned Precision>
struct BufferParser<MultiPrecision<Precision>> : detail::BufferParserBase<MultiPrecision<Precision>> {
    using BaseType = detail::BufferParserBase<MultiPrecision<Precision>>;
    using BaseType::BaseType;
    using NumberType = boost::multiprecision::cpp_dec_float<Precision>;
 
    void operator()(const FieldBuffer& buffer) {
        auto str = detail::NumericBufferToString(buffer);
        // cpp_dec_float provides const char* constructor, where it parses the
        // contents to internal buffers. no std::string constructor is provided.
        this->value = NumberType{str.c_str()};
    }
};
 
template <unsigned Precision>
struct CppToSystemPg<MultiPrecision<Precision>> : PredefinedOid<PredefinedOids::kNumeric> {};
 
}  // namespace io
}  // namespace storages::postgres
 
USERVER_NAMESPACE_END