From 3c9ae28cf54f02c41310ad40a7085be0209e733a Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 17 Jun 2016 01:41:21 +0100
Subject: Add RowRange and supporting classes for use with for loop over a
 selected rowset

---
 libdbpp/selectcommand.cpp        | 17 ++++++++++
 libdbpp/selectcommand.h          | 55 ++++++++++++++++++++++++++++++++
 libdbpp/selectcommandUtil.impl.h | 69 ++++++++++++++++++++++++++++++++++++++++
 libdbpp/unittests/testUtils.cpp  | 20 ++++++++++++
 4 files changed, 161 insertions(+)

diff --git a/libdbpp/selectcommand.cpp b/libdbpp/selectcommand.cpp
index 7106fb6..6f36aa5 100644
--- a/libdbpp/selectcommand.cpp
+++ b/libdbpp/selectcommand.cpp
@@ -71,3 +71,20 @@ DB::SelectCommand::insertColumn(ColumnPtr col)
 	return *columns->insert(col).first;
 }
 
+DB::RowBase::RowBase(SelectCommand * s) :
+	sel(s)
+{
+}
+
+const DB::Column&
+DB::RowBase::operator[](const Glib::ustring & n) const
+{
+	return sel->operator[](n);
+}
+
+const DB::Column&
+DB::RowBase::operator[](unsigned int col) const
+{
+	return sel->operator[](col);
+}
+
diff --git a/libdbpp/selectcommand.h b/libdbpp/selectcommand.h
index c29084a..5e48f4d 100644
--- a/libdbpp/selectcommand.h
+++ b/libdbpp/selectcommand.h
@@ -16,6 +16,58 @@
 
 namespace DB {
 	class Column;
+	class SelectCommand;
+
+	/// @cond
+	class DLL_PUBLIC RowBase {
+		public:
+			RowBase(SelectCommand *);
+
+			/// Get a column reference by index.
+			const Column & operator[](unsigned int col) const;
+			/// Get a column reference by name.
+			const Column & operator[](const Glib::ustring &) const;
+
+		protected:
+			SelectCommand * sel;
+	};
+
+	template<typename ... Fn>
+	class Row : public RowBase {
+		public:
+			Row(SelectCommand *);
+
+			/// Get value of column C in current row.
+			template<unsigned int C>
+			typename std::tuple_element<C, std::tuple<Fn...>>::type value() const;
+	};
+
+	template<typename ... Fn>
+	class RowRangeIterator {
+		public:
+			RowRangeIterator(SelectCommand *);
+
+			bool operator!=(const RowRangeIterator &) const;
+			void operator++();
+			Row<Fn...> operator*() const;
+
+		private:
+			SelectCommand * sel;
+			bool validRow;
+	};
+
+	template<typename ... Fn>
+	class RowRange {
+		public:
+			RowRange(SelectCommand *);
+
+			RowRangeIterator<Fn...> begin() const;
+			RowRangeIterator<Fn...> end() const;
+
+		private:
+			SelectCommand * sel;
+	};
+	/// @endcond
 
 	/// Exception thrown when the requested column is outside the range of the result set.
 	class DLL_PUBLIC ColumnIndexOutOfRange : public AdHoc::Exception<Error> {
@@ -67,6 +119,9 @@ namespace DB {
 			/// Push each row through a function accepting one value per column
 			template<typename ... Fn, typename Func = boost::function<void(Fn...)>>
 			void forEachRow(const Func & func);
+			/// Support for a C++ row range for
+			template<typename ... Fn>
+			RowRange<Fn...> as();
 
 		protected:
 			/// Helper function so clients need not know about boost::multi_index_container.
diff --git a/libdbpp/selectcommandUtil.impl.h b/libdbpp/selectcommandUtil.impl.h
index 26e9635..4c0e035 100644
--- a/libdbpp/selectcommandUtil.impl.h
+++ b/libdbpp/selectcommandUtil.impl.h
@@ -30,6 +30,75 @@ namespace DB {
 			forEachField<std::tuple<Fn...>, Func, 0>(this, func);
 		}
 	}
+
+	template<typename ... Fn>
+	inline RowRange<Fn...> SelectCommand::as()
+	{
+		return RowRange<Fn...>(this);
+	}
+
+	template<typename ... Fn>
+	inline RowRange<Fn...>::RowRange(SelectCommand * s) :
+		sel(s)
+	{
+	}
+
+	template<typename ... Fn>
+	inline RowRangeIterator<Fn...> RowRange<Fn...>::begin() const
+	{
+		return RowRangeIterator<Fn...>(sel);
+	}
+
+	template<typename ... Fn>
+	inline RowRangeIterator<Fn...> RowRange<Fn...>::end() const
+	{
+		return RowRangeIterator<Fn...>(nullptr);
+	}
+
+	template<typename ... Fn>
+	inline RowRangeIterator<Fn...>::RowRangeIterator(SelectCommand * s) :
+		sel(s)
+	{
+		if (sel) {
+			validRow = sel->fetch();
+		}
+		else {
+			validRow = false;
+		}
+	}
+
+	template<typename ... Fn>
+	inline bool RowRangeIterator<Fn...>::operator!=(const RowRangeIterator &) const
+	{
+		return validRow;
+	}
+
+	template<typename ... Fn>
+	inline void RowRangeIterator<Fn...>::operator++()
+	{
+		validRow = sel->fetch();
+	}
+
+	template<typename ... Fn>
+	inline Row<Fn...> RowRangeIterator<Fn...>::operator*() const
+	{
+		return Row<Fn...>(sel);
+	}
+
+	template<typename ... Fn>
+	inline Row<Fn...>::Row(SelectCommand * s) :
+		RowBase(s)
+	{
+	}
+
+	template<typename ... Fn>
+	template<unsigned int C>
+	inline typename std::tuple_element<C, std::tuple<Fn...>>::type Row<Fn...>::value() const
+	{
+		typename std::tuple_element<C, std::tuple<Fn...>>::type a;
+		sel->operator[](C) >> a;
+		return a;
+	}
 }
 /// @endcond
 
diff --git a/libdbpp/unittests/testUtils.cpp b/libdbpp/unittests/testUtils.cpp
index 4c269e9..ac9b7c1 100644
--- a/libdbpp/unittests/testUtils.cpp
+++ b/libdbpp/unittests/testUtils.cpp
@@ -50,6 +50,26 @@ BOOST_AUTO_TEST_CASE( forEachRowNulls )
 			});
 }
 
+BOOST_AUTO_TEST_CASE( stdforOverRows )
+{
+	auto db = DB::ConnectionPtr(DB::MockDatabase::openConnectionTo("pqmock"));
+	unsigned int count = 0;
+	int64_t totalOfa = 0;
+	std::string totalOfc;
+	auto sel = db->select("SELECT a, c FROM forEachRow ORDER BY a DESC");
+	for (const auto & row : sel->as<int64_t, std::string>()) {
+		count += 1;
+		BOOST_REQUIRE_EQUAL("a", row[0].name);
+		BOOST_REQUIRE_EQUAL(1, row["c"].colNo);
+		int64_t a = row.value<0>();
+		totalOfa += a;
+		totalOfc += row.value<1>();
+	}
+	BOOST_REQUIRE_EQUAL(count, 2);
+	BOOST_REQUIRE_EQUAL(totalOfa, 3);
+	BOOST_REQUIRE_EQUAL(totalOfc, "Some textSome text");
+}
+
 BOOST_AUTO_TEST_CASE( execute )
 {
 	auto db = DB::ConnectionPtr(DB::MockDatabase::openConnectionTo("pqmock"));
-- 
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