Merge pull request #482 from leapmotion/feature-nowaitbarrier

Add timeout-free Barrier variant

autowiring/DispatchQueue.h

@@ -200,6 +200,11 @@ class DispatchQueue {
   /// </remarks>
   bool Barrier(std::chrono::nanoseconds timeout);
 
+  /// <summary>
+  /// Identical to the timed version of Barrier, but does not time out
+  /// </summary>
+  void Barrier(void);
+
   /// <summary>
   /// Recommends a point in time to wake up to check for events
   /// </summary>

src/autowiring/DispatchQueue.cpp

@@ -193,6 +193,21 @@ bool DispatchQueue::Barrier(std::chrono::nanoseconds timeout) {
   return rv;
 }
 
+void DispatchQueue::Barrier(void) {
+  // Set up the lambda:
+  bool complete = false;
+  *this += [&] { complete = true; };
+
+  // Obtain the lock, wait until our variable is satisfied, which might be right away:
+  std::unique_lock<std::mutex> lk(m_dispatchLock);
+  m_queueUpdated.wait(lk, [&] { return m_aborted || complete; });
+  if (m_aborted)
+    // At this point, the dispatch queue MUST be completely run down.  We have no outstanding references
+    // to our stack-allocated "complete" variable.  Furthermore, after m_aborted is true, no further
+    // dispatchers are permitted to be run.
+    throw autowiring_error("Dispatch queue was aborted while a barrier was invoked");
+}
+
 std::chrono::steady_clock::time_point
 DispatchQueue::SuggestSoonestWakeupTimeUnsafe(std::chrono::steady_clock::time_point latestTime) const {
   return

src/autowiring/test/DispatchQueueTest.cpp

@@ -129,4 +129,4 @@ TEST_F(DispatchQueueTest, BarrierWithAbort) {
   ct->Abort();
   ASSERT_EQ(std::future_status::ready, f.wait_for(std::chrono::seconds(5))) << "Barrier did not abort fast enough";
   ASSERT_TRUE(*exception) << "Exception should have been thrown inside the Barrier call";
-}
+}