Experimental parameter<> support for #71

Author: d-frey

CMakeLists.txt

@@ -46,6 +46,7 @@ set(taopq_INCLUDE_FILES
   ${taopq_INCLUDE_DIRS}/tao/pq/notification.hpp
   ${taopq_INCLUDE_DIRS}/tao/pq/null.hpp
   ${taopq_INCLUDE_DIRS}/tao/pq/oid.hpp
+  ${taopq_INCLUDE_DIRS}/tao/pq/parameter.hpp
   ${taopq_INCLUDE_DIRS}/tao/pq/parameter_traits.hpp
   ${taopq_INCLUDE_DIRS}/tao/pq/parameter_traits_aggregate.hpp
   ${taopq_INCLUDE_DIRS}/tao/pq/parameter_traits_array.hpp

include/tao/pq/parameter.hpp

@@ -0,0 +1,100 @@
+// Copyright (c) 2023 Daniel Frey and Dr. Colin Hirsch
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef TAO_PQ_PARAMETER_HPP
+#define TAO_PQ_PARAMETER_HPP
+
+#include <cassert>
+#include <cstddef>
+#include <memory>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#include <tao/pq/oid.hpp>
+#include <tao/pq/parameter_traits.hpp>
+
+namespace tao::pq
+{
+   class transaction;
+
+   // NOTE: for now, this is experimental and might change or vanish at any time!
+   // TODO: naming?
+   template< std::size_t Max = 16 >
+   class parameter
+   {
+   private:
+      struct binder
+      {
+         virtual ~binder() = default;
+      };
+
+      template< typename T >
+      class traits_binder : public binder
+      {
+      private:
+         const parameter_traits< T > m_traits;
+
+      public:
+         explicit traits_binder( const T& t ) noexcept( noexcept( parameter_traits< T >( t ) ) )
+            : m_traits( t )
+         {}
+
+         template< std::size_t... Is >
+         void fill( Oid* types, const char** values, int* lengths, int* formats, std::index_sequence< Is... > /*unused*/ ) const  // TODO: noexcept( ... )?
+         {
+            ( ( types[ Is ] = static_cast< Oid >( m_traits.template type< Is >() ) ), ... );
+            ( ( values[ Is ] = m_traits.template value< Is >() ), ... );
+            ( ( lengths[ Is ] = m_traits.template length< Is >() ), ... );
+            ( ( formats[ Is ] = m_traits.template format< Is >() ), ... );
+         }
+      };
+
+      std::size_t m_pos = 0;
+      std::unique_ptr< binder > m_binder[ Max ];
+
+      std::size_t m_size = 0;
+      Oid m_types[ Max ];
+      const char* m_values[ Max ];
+      int m_lengths[ Max ];
+      int m_formats[ Max ];
+
+      friend class transaction;
+
+      template< typename A >
+      void bind_impl( const A& a )  // TODO: protect against binding temporaries!
+      {
+         constexpr auto columns = parameter_traits< std::decay_t< const A& > >::columns;
+         if( m_size + columns > Max ) {
+            throw std::length_error( "too many parameters!" );
+         }
+
+         auto* bptr = new traits_binder< std::decay_t< const A& > >( a );
+         m_binder[ m_pos++ ].reset( bptr );
+
+         bptr->fill( &m_types[ m_size ], &m_values[ m_size ], &m_lengths[ m_size ], &m_formats[ m_size ], std::make_index_sequence< columns >() );
+         m_size += columns;
+      }
+
+   public:
+      // NOTE: arguments must remain VALID and UNMODIFIED until this object is destroyed or reset.
+      template< typename... As >
+      void bind( As&&... as )
+      {
+         ( bind_impl( std::forward< As >( as ) ), ... );
+      }
+
+      void reset() noexcept
+      {
+         for( std::size_t i = 0; i < m_pos; ++i ) {
+            m_binder[ i ].reset();
+         }
+         m_pos = 0;
+         m_size = 0;
+      }
+   };
+
+}  // namespace tao::pq
+
+#endif

include/tao/pq/transaction.hpp

@@ -19,6 +19,7 @@
 #include <tao/pq/internal/gen.hpp>
 #include <tao/pq/internal/zsv.hpp>
 #include <tao/pq/oid.hpp>
+#include <tao/pq/parameter.hpp>
 #include <tao/pq/parameter_traits.hpp>
 #include <tao/pq/result.hpp>
 
@@ -104,6 +105,18 @@ namespace tao::pq
          }
       }
 
+      template< std::size_t Max >
+      void send( const internal::zsv statement, const parameter< Max >& as )
+      {
+         send_params( statement, as.m_size, as.m_types, as.m_values, as.m_lengths, as.m_formats );
+      }
+
+      template< std::size_t Max >
+      void send( const internal::zsv statement, parameter< Max >& as )
+      {
+         send( statement, const_cast< const parameter< Max >& >( as ) );
+      }
+
       [[nodiscard]] auto get_result( const std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now() ) -> result;
 
       template< typename... As >

src/test/pq/parameter.cpp

@@ -0,0 +1,77 @@
+// Copyright (c) 2023 Daniel Frey and Dr. Colin Hirsch
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+
+#include "../getenv.hpp"
+#include "../macros.hpp"
+
+#include <iostream>
+#include <tao/pq.hpp>
+
+void run()
+{
+   // overwrite the default with an environment variable if needed
+   const auto connection_string = tao::pq::internal::getenv( "TAOPQ_TEST_DATABASE", "dbname=template1" );
+
+   // open a connection to the database
+   const auto conn = tao::pq::connection::create( connection_string );
+
+   // execute statements
+   conn->execute( "DROP TABLE IF EXISTS tao_parameter" );
+   conn->execute( "CREATE TABLE tao_parameter ( name TEXT PRIMARY KEY, age INTEGER NOT NULL )" );
+
+   // prepare statements
+   conn->prepare( "insert_user", "INSERT INTO tao_parameter ( name, age ) VALUES ( $1, $2 )" );
+
+   {
+      // begin transaction
+      const auto tr = conn->transaction();
+
+      // execute previously prepared statements
+      {
+         tao::pq::parameter p;
+         p.bind( "Daniel", 42 );
+         tr->execute( "insert_user", p );
+         p.reset();
+         p.bind( "Tom" );
+         p.bind( 41 );
+         tr->execute( "insert_user", p );
+      }
+
+      {
+         tao::pq::parameter< 2 > p;
+         p.bind( "Jerry" );
+         p.bind( 29 );
+         tr->execute( "insert_user", p );
+      }
+
+      // commit transaction
+      tr->commit();
+   }
+
+   // query data
+   const auto users = conn->execute( "SELECT name, age FROM tao_parameter WHERE age >= $1", 40 );
+
+   // iterate and convert results
+   for( const auto& row : users ) {
+      std::cout << row[ "name" ].as< std::string >() << " is "
+                << row[ "age" ].as< unsigned >() << " years old.\n";
+   }
+}
+
+auto main() -> int
+{
+   try {
+      run();
+   }
+   // LCOV_EXCL_START
+   catch( const std::exception& e ) {
+      std::cerr << "exception: " << e.what() << std::endl;
+      throw;
+   }
+   catch( ... ) {
+      std::cerr << "unknown exception" << std::endl;
+      throw;
+   }
+   // LCOV_EXCL_STOP
+}