From 49129dc36008682f5f105e576af279ba84b7b5e1 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 29 Dec 2015 02:12:20 +0000
Subject: Add scope transaction helper

---
 libdbpp/connection.cpp               | 16 ++++++++++++++++
 libdbpp/connection.h                 | 14 ++++++++++++++
 libdbpp/unittests/testConnection.cpp | 30 +++++++++++++++++++++++++-----
 3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/libdbpp/connection.cpp b/libdbpp/connection.cpp
index 333becb..1624ce6 100644
--- a/libdbpp/connection.cpp
+++ b/libdbpp/connection.cpp
@@ -74,6 +74,22 @@ DB::TransactionRequired::TransactionRequired() :
 {
 }
 
+DB::TransactionScope::TransactionScope(DB::Connection * c) :
+	conn(c)
+{
+	conn->beginTx();
+}
+
+DB::TransactionScope::~TransactionScope()
+{
+	if (std::uncaught_exception()) {
+		conn->rollbackTx();
+	}
+	else {
+		conn->commitTx();
+	}
+}
+
 INSTANTIATEFACTORY(DB::Connection, std::string);
 PLUGINRESOLVER(DB::ConnectionFactory, DB::Connection::resolvePlugin);
 
diff --git a/libdbpp/connection.h b/libdbpp/connection.h
index a15a9ab..e34315a 100644
--- a/libdbpp/connection.h
+++ b/libdbpp/connection.h
@@ -133,6 +133,20 @@ namespace DB {
 		private:
 	};
 
+	/// Helper class for beginning/committing/rolling back transactions in accordance with scope and exceptions.
+	class DLL_PUBLIC TransactionScope {
+		public:
+			/// Create a new helper and associated transaction on the given connection.
+			TransactionScope(DB::Connection *);
+			~TransactionScope();
+
+		private:
+			TransactionScope(const TransactionScope &) = delete;
+			void operator=(const TransactionScope &) = delete;
+
+			Connection * conn;
+	};
+
 	typedef boost::shared_ptr<Connection> ConnectionPtr;
 	typedef AdHoc::Factory<Connection, std::string> ConnectionFactory;
 }
diff --git a/libdbpp/unittests/testConnection.cpp b/libdbpp/unittests/testConnection.cpp
index 159e5a2..76758a7 100644
--- a/libdbpp/unittests/testConnection.cpp
+++ b/libdbpp/unittests/testConnection.cpp
@@ -12,13 +12,13 @@
 // LCOV_EXCL_START
 class MockDb : public DB::Connection {
 	public:
-		MockDb(const std::string &) {}
+		MockDb(const std::string &) : txDepth(0) {}
 
 		void	finish() const {}
-		int		beginTx() const { return 0; }
-		int		commitTx() const { return 0; }
-		int		rollbackTx() const { return 0; }
-		bool	inTx() const { return false; }
+		int		beginTx() const { return ++txDepth; }
+		int		commitTx() const { return --txDepth; }
+		int		rollbackTx() const { return --txDepth; }
+		bool	inTx() const { return txDepth > 0; }
 		void	ping() const {}
 		DB::BulkDeleteStyle bulkDeleteStyle() const { return DB::BulkDeleteUsingUsing; }
 		DB::BulkUpdateStyle bulkUpdateStyle() const { return DB::BulkUpdateUsingJoin; }
@@ -34,6 +34,7 @@ class MockDb : public DB::Connection {
 		size_t bulkUploadData(const char *, size_t) const {return 0;}
 
 		mutable std::vector<std::string> executed;
+		mutable unsigned int txDepth;
 };
 // LCOV_EXCL_STOP
 
@@ -126,6 +127,25 @@ BOOST_AUTO_TEST_CASE( parse2 )
 	s.close();
 }
 
+BOOST_AUTO_TEST_CASE( txscope )
+{
+	auto mock = DB::ConnectionFactory::createNew("MockDb", "doesn't matter");
+	BOOST_REQUIRE(mock);
+	BOOST_REQUIRE_EQUAL(false, mock->inTx());
+	{
+		DB::TransactionScope tx(mock);
+		BOOST_REQUIRE_EQUAL(true, mock->inTx());
+	}
+	BOOST_REQUIRE_EQUAL(false, mock->inTx());
+	try {
+		DB::TransactionScope tx(mock);
+		BOOST_REQUIRE_EQUAL(true, mock->inTx());
+		throw std::exception();
+	}
+	catch (...) {
+		BOOST_REQUIRE_EQUAL(false, mock->inTx());
+	}
+}
 
 BOOST_AUTO_TEST_CASE( savepoints )
 {
-- 
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