Relocating everything in the repo s.t. it can be merged into

the columnstore repo.

storage-manager/src/RWLock.h

@@ -0,0 +1,52 @@
+/* Copyright (C) 2019 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+#include <boost/thread/mutex.hpp>
+#include <boost/thread/condition.hpp>
+
+/* Quicky impl of a read-write lock that prioritizes writers. */
+namespace storagemanager
+{
+    class RWLock
+    {
+        public:
+            RWLock();
+            ~RWLock();
+            
+            void readLock();
+            // this version will release the lock in the parameter after locking this instance
+            void readLock(boost::unique_lock<boost::mutex> &);
+            void readUnlock();
+            void writeLock();
+            // this version will release the lock in the parameter after locking this instance
+            void writeLock(boost::unique_lock<boost::mutex> &);
+            void writeUnlock();
+            
+            // returns true if anything is blocked on or owns this lock instance.
+            bool inUse();
+            
+        private:
+            uint readersWaiting;
+            uint readersRunning;
+            uint writersWaiting;
+            uint writersRunning;
+            boost::mutex m;
+            boost::condition okToWrite;
+            boost::condition okToRead;
+    };
+}
+