Bug 1374594 - Allow mutex/monitor scoped unlockers to be constructed from their locking counterparts - r=froydnj

MozReview-Commit-ID: 7PResfLcEeO

--HG--
extra : rebase_source : aab88391ef689bf92742a0ef37729d664dd528b3

xpcom/threads/Monitor.h

@@ -97,6 +97,8 @@ private:
   MonitorAutoLock& operator=(const MonitorAutoLock&);
   static void* operator new(size_t) CPP_THROW_NEW;
 
+  friend class MonitorAutoUnlock;
+
   Monitor* mMonitor;
 };
 
@@ -116,6 +118,12 @@ public:
     mMonitor->Unlock();
   }
 
+  explicit MonitorAutoUnlock(MonitorAutoLock& aMonitorLock)
+    : mMonitor(aMonitorLock.mMonitor)
+  {
+    mMonitor->Unlock();
+  }
+
   ~MonitorAutoUnlock()
   {
     mMonitor->Lock();

xpcom/threads/Mutex.h

@@ -136,6 +136,9 @@ private:
   Mutex& operator=(const Mutex&);
 };
 
+template<typename T>
+class MOZ_RAII BaseAutoUnlock;
+
 /**
  * MutexAutoLock
  * Acquires the Mutex when it enters scope, and releases it when it leaves
@@ -174,6 +177,8 @@ private:
   BaseAutoLock& operator=(BaseAutoLock&);
   static void* operator new(size_t) CPP_THROW_NEW;
 
+  friend class BaseAutoUnlock<T>;
+
   T* mLock;
   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
 };
@@ -200,6 +205,15 @@ public:
     mLock->Unlock();
   }
 
+  explicit BaseAutoUnlock(
+    BaseAutoLock<T>& aAutoLock MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : mLock(aAutoLock.mLock)
+  {
+    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+    NS_ASSERTION(mLock, "null lock");
+    mLock->Unlock();
+  }
+
   ~BaseAutoUnlock()
   {
     mLock->Lock();

xpcom/threads/ReentrantMonitor.h

@@ -199,6 +199,8 @@ private:
   ReentrantMonitorAutoEnter& operator=(const ReentrantMonitorAutoEnter&);
   static void* operator new(size_t) CPP_THROW_NEW;
 
+  friend class ReentrantMonitorAutoExit;
+
   mozilla::ReentrantMonitor* mReentrantMonitor;
 };
 
@@ -229,6 +231,15 @@ public:
     mReentrantMonitor->Exit();
   }
 
+  explicit ReentrantMonitorAutoExit(
+    ReentrantMonitorAutoEnter& aReentrantMonitorAutoEnter)
+    : mReentrantMonitor(aReentrantMonitorAutoEnter.mReentrantMonitor)
+  {
+    NS_ASSERTION(mReentrantMonitor, "null monitor");
+    mReentrantMonitor->AssertCurrentThreadIn();
+    mReentrantMonitor->Exit();
+  }
+
   ~ReentrantMonitorAutoExit(void)
   {
     mReentrantMonitor->Enter();