Add -[transactionWithBlock:]

FossilOrigin-Name: 1ecc15c9b801a9531314936f644a43a863fc7811768c7c257b409adad349d6e6

src/SL3Connection.h

@@ -44,6 +44,9 @@ OF_ASSUME_NONNULL_BEGIN
 		       flags: (int)flags OF_DESIGNATED_INITIALIZER;
 - (SL3PreparedStatement *)prepareStatement: (OFConstantString *)SQL;
 - (void)executeStatement: (OFConstantString *)SQL;
+#ifdef OF_HAVE_BLOCKS
+- (void)transactionWithBlock: (bool (^)(void))block;
+#endif
 @end
 
 OF_ASSUME_NONNULL_END

src/SL3Connection.m

@@ -90,4 +90,25 @@
 		    exceptionWithConnection: self
 				  errorCode: code];
 }
+
+#ifdef OF_HAVE_BLOCKS
+- (void)transactionWithBlock: (bool (^)(void))block
+{
+	bool commit;
+
+	[self executeStatement: @"BEGIN TRANSACTION"];
+
+	@try {
+		commit = block();
+	} @catch (id e) {
+		[self executeStatement: @"ROLLBACK TRANSACTION"];
+		@throw e;
+	}
+
+	if (commit)
+		[self executeStatement: @"COMMIT TRANSACTION"];
+	else
+		[self executeStatement: @"ROLLBACK TRANSACTION"];
+}
+#endif
 @end