detail/typing/pos_map.hpp

0001 //
0002 // Copyright (c) 2019-2025 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
0003 //
0004 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0005 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007
0008 #ifndef BOOST_MYSQL_DETAIL_TYPING_POS_MAP_HPP
0009 #define BOOST_MYSQL_DETAIL_TYPING_POS_MAP_HPP
0010
0011 #include <boost/mysql/field_view.hpp>
0012 #include <boost/mysql/metadata.hpp>
0013 #include <boost/mysql/metadata_collection_view.hpp>
0014 #include <boost/mysql/string_view.hpp>
0015
0016 #include <boost/assert.hpp>
0017 #include <boost/config.hpp>
0018 #include <boost/core/span.hpp>
0019
0020 #include <cstddef>
0021
0022 namespace boost {
0023 namespace mysql {
0024 namespace detail {
0025
0026 // These functions map C++ type positions to positions to positions in the DB query
0027
0028 BOOST_INLINE_CONSTEXPR std::size_t pos_absent = static_cast<std::size_t>(-1);
0029 using name_table_t = boost::span<const string_view>;
0030
0031 inline bool has_field_names(name_table_t name_table) noexcept { return !name_table.empty(); }
0032
0033 inline void pos_map_reset(span<std::size_t> self) noexcept
0034 {
0035     for (std::size_t i = 0; i < self.size(); ++i)
0036         self.data()[i] = pos_absent;
0037 }
0038
0039 inline void pos_map_add_field(
0040     span<std::size_t> self,
0041     name_table_t name_table,
0042     std::size_t db_index,
0043     string_view field_name
0044 ) noexcept
0045 {
0046     if (has_field_names(name_table))
0047     {
0048         BOOST_ASSERT(self.size() == name_table.size());
0049
0050         // We're mapping fields by name. Try to find where in our target struct
0051         // is the current field located
0052         auto it = std::find(name_table.begin(), name_table.end(), field_name);
0053         if (it != name_table.end())
0054         {
0055             std::size_t cpp_index = it - name_table.begin();
0056             self[cpp_index] = db_index;
0057         }
0058     }
0059     else
0060     {
0061         // We're mapping by position. Any extra trailing fields are discarded
0062         if (db_index < self.size())
0063         {
0064             self[db_index] = db_index;
0065         }
0066     }
0067 }
0068
0069 inline field_view map_field_view(
0070     span<const std::size_t> self,
0071     std::size_t cpp_index,
0072     span<const field_view> array
0073 ) noexcept
0074 {
0075     BOOST_ASSERT(cpp_index < self.size());
0076     return array[self[cpp_index]];
0077 }
0078
0079 inline const metadata& map_metadata(
0080     span<const std::size_t> self,
0081     std::size_t cpp_index,
0082     metadata_collection_view meta
0083 ) noexcept
0084 {
0085     BOOST_ASSERT(cpp_index < self.size());
0086     return meta[self[cpp_index]];
0087 }
0088
0089 }  // namespace detail
0090 }  // namespace mysql
0091 }  // namespace boost
0092
0093 #endif