added readwritelock implementation

Author: Plamen5kov

runtime/src/main/jni/ReadWriteLock.cpp

@@ -0,0 +1,57 @@
+//
+// Created by plamen5kov on 9/10/16.
+//
+
+#include "ReadWriteLock.h"
+
+using namespace std;
+using namespace tns;
+
+ReadWriteLock::ReadWriteLock()
+        : shared(), reader_gate(), writer_gate(), active_readers(0), waiting_writers(0), active_writers(0)
+{
+}
+
+void ReadWriteLock::AquireReadLock() {
+    //wait till there are no waiting writers and increment active readers
+    std::unique_lock<std::mutex> lk(shared);
+    while( waiting_writers != 0 ) //starving readers and giving writer priority
+    {
+        reader_gate.wait(lk);
+    }
+    active_readers++;
+    lk.unlock();
+}
+
+void ReadWriteLock::ReleaseReadUnlock() {
+    //get lock decrement active readers and notify one waiting writer
+    std::unique_lock<std::mutex> lk(shared);
+    active_readers--;
+    lk.unlock();
+    writer_gate.notify_one();
+}
+
+void ReadWriteLock::AquireWriteLock() {
+    //declare waiting and wait till there are no more active readers or writers and get lock
+    std::unique_lock<std::mutex> lk(shared);
+    waiting_writers++;
+    while( active_readers != 0 || active_writers != 0 ) //if any is active wait for them to finish
+    {
+        writer_gate.wait(lk);
+    }
+    active_writers++;
+    lk.unlock();
+}
+
+void ReadWriteLock::ReleaseWriteUnlock() {
+    //decrement waiting and active writers
+    std::unique_lock<std::mutex> lk(shared);
+    waiting_writers--;
+    active_writers--;
+    if(waiting_writers > 0)
+        writer_gate.notify_one(); //(priority to writers)
+    else
+        reader_gate.notify_all(); //notify readers
+    lk.unlock();
+}
+

runtime/src/main/jni/ReadWriteLock.h

@@ -0,0 +1,34 @@
+//
+// Created by plamen5kov on 9/10/16.
+//
+
+#ifndef READWRITELOCK_H
+#define READWRITELOCK_H
+
+#include <iostream>
+#include <mutex>
+#include <condition_variable>
+
+namespace tns {
+
+    class ReadWriteLock
+    {
+        public:
+            ReadWriteLock();
+
+            void AquireReadLock();
+            void ReleaseReadUnlock();
+            void AquireWriteLock();
+            void ReleaseWriteUnlock();
+
+        private:
+            std::mutex shared;
+            std::condition_variable reader_gate;
+            std::condition_variable writer_gate;
+            int active_readers;
+            int active_writers;
+            int waiting_writers;
+        };
+}
+
+#endif //READWRITELOCK_H