Implemented std::experimental optional and consolidated the different optional implementations

Author: cbeiraod

hdr/sqlite_modern_cpp.h

@@ -26,13 +26,20 @@
 #endif
 
 #ifdef MODERN_SQLITE_STD_OPTIONAL_SUPPORT
-#include <optional>
+  #include <optional>
+  template<class T>
+  using optional = std::optional<T>;
+  #define MODERN_SQLITE_OPTIONAL_SUPPORT
 #elif _MODERN_SQLITE_EXPERIMENTAL_OPTIONAL_SUPPORT && __has_include(<experimental/optional>)
-#include <experimental/optional>
-#endif
-
-#ifdef _MODERN_SQLITE_BOOST_OPTIONAL_SUPPORT
-#include <boost/optional.hpp>
+  #include <experimental/optional>
+  template<class T>
+  using optional = std::experimental::optional<T>;
+  #define MODERN_SQLITE_OPTIONAL_SUPPORT
+#elif _MODERN_SQLITE_BOOST_OPTIONAL_SUPPORT
+  #include <boost/optional.hpp>
+  template<class T>
+  using optional = boost::optional<T>;
+  #define MODERN_SQLITE_OPTIONAL_SUPPORT
 #endif
 
 #include <sqlite3.h>
@@ -239,14 +246,9 @@ namespace sqlite {
 		friend database_binder& operator <<(database_binder& db, const std::u16string& txt);
 
 
-#ifdef MODERN_SQLITE_STD_OPTIONAL_SUPPORT
-		template <typename OptionalT> friend database_binder& operator <<(database_binder& db, const std::optional<OptionalT>& val);
-		template <typename OptionalT> friend void get_col_from_db(database_binder& db, int inx, std::optional<OptionalT>& o);
-#endif
-
-#ifdef _MODERN_SQLITE_BOOST_OPTIONAL_SUPPORT
-		template <typename BoostOptionalT> friend database_binder& operator <<(database_binder& db, const boost::optional<BoostOptionalT>& val);
-		template <typename BoostOptionalT> friend void get_col_from_db(database_binder& db, int inx, boost::optional<BoostOptionalT>& o);
+#ifdef MODERN_SQLITE_OPTIONAL_SUPPORT
+		template <typename OptionalT> friend database_binder& operator <<(database_binder& db, const optional<OptionalT>& val);
+		template <typename OptionalT> friend void get_col_from_db(database_binder& db, int inx, optional<OptionalT>& o);
 #endif
 
 	public:
@@ -790,23 +792,23 @@ namespace sqlite {
 		val = i;
 	}
 
-	// std::optional support for NULL values
-#ifdef MODERN_SQLITE_STD_OPTIONAL_SUPPORT
-	template <typename OptionalT> inline database_binder& operator <<(database_binder& db, const std::optional<OptionalT>& val) {
+	// optional support for NULL values, whether std::optional, std::experimental::optional or boost:optional
+#ifdef MODERN_SQLITE_OPTIONAL_SUPPORT
+	template <typename OptionalT> inline database_binder& operator <<(database_binder& db, const optional<OptionalT>& val) {
 		if(val) {
 			return db << std::move(*val);
 		} else {
 			return db << nullptr;
 		}
 	}
-	template <typename OptionalT> inline void store_result_in_db(sqlite3_context* db, const std::optional<OptionalT>& val) {
+	template <typename OptionalT> inline void store_result_in_db(sqlite3_context* db, const optional<OptionalT>& val) {
 		if(val) {
 			store_result_in_db(db, *val);
 		}
 		sqlite3_result_null(db);
 	}
 
-	template <typename OptionalT> inline void get_col_from_db(database_binder& db, int inx, std::optional<OptionalT>& o) {
+	template <typename OptionalT> inline void get_col_from_db(database_binder& db, int inx, optional<OptionalT>& o) {
 		if(sqlite3_column_type(db._stmt.get(), inx) == SQLITE_NULL) {
 			o.reset();
 		} else {
@@ -815,7 +817,7 @@ namespace sqlite {
 			o = std::move(v);
 		}
 	}
-	template <typename OptionalT> inline void get_val_from_db(sqlite3_value *value, std::optional<OptionalT>& o) {
+	template <typename OptionalT> inline void get_val_from_db(sqlite3_value *value, optional<OptionalT>& o) {
 		if(sqlite3_value_type(value) == SQLITE_NULL) {
 			o.reset();
 		} else {
@@ -826,42 +828,6 @@ namespace sqlite {
 	}
 #endif
 
-	// boost::optional support for NULL values
-#ifdef _MODERN_SQLITE_BOOST_OPTIONAL_SUPPORT
-	template <typename BoostOptionalT> inline database_binder& operator <<(database_binder& db, const boost::optional<BoostOptionalT>& val) {
-		if(val) {
-			return db << std::move(*val);
-		} else {
-			return db << nullptr;
-		}
-	}
-	template <typename BoostOptionalT> inline void store_result_in_db(sqlite3_context* db, const boost::optional<BoostOptionalT>& val) {
-		if(val) {
-			store_result_in_db(db, *val);
-		}
-		sqlite3_result_null(db);
-	}
-
-	template <typename BoostOptionalT> inline void get_col_from_db(database_binder& db, int inx, boost::optional<BoostOptionalT>& o) {
-		if(sqlite3_column_type(db._stmt.get(), inx) == SQLITE_NULL) {
-			o.reset();
-		} else {
-			BoostOptionalT v;
-			get_col_from_db(db, inx, v);
-			o = std::move(v);
-		}
-	}
-	template <typename BoostOptionalT> inline void get_val_from_db(sqlite3_value *value, boost::optional<BoostOptionalT>& o) {
-		if(sqlite3_value_type(value) == SQLITE_NULL) {
-			o.reset();
-		} else {
-			BoostOptionalT v;
-			get_val_from_db(value, v);
-			o = std::move(v);
-		}
-	}
-#endif
-
 #ifdef MODERN_SQLITE_STD_VARIANT_SUPPORT
 	template <typename ...Args> inline database_binder& operator <<(database_binder& db, const std::variant<Args...>& val) {
 		std::visit([&](auto &&opt) {db << std::forward<decltype(opt)>(opt);}, val);