1 files changed, 239 insertions, 0 deletions
diff --git a/xbmc/threads/Event.h b/xbmc/threads/Event.h
new file mode 100644
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--- /dev/null
+++ b/xbmc/threads/Event.h
@@ -0,0 +1,239 @@
+/*
+ *  Copyright (C) 2005-2018 Team Kodi
+ *  This file is part of Kodi - https://kodi.tv
+ *
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ *  See LICENSES/README.md for more information.
+ */
+
+#pragma once
+
+#include "threads/Condition.h"
+
+#include <initializer_list>
+#include <memory>
+#include <mutex>
+#include <vector>
+
+// forward declare the CEventGroup
+namespace XbmcThreads
+{
+class CEventGroup;
+}
+
+/**
+ * @brief This is an Event class built from a ConditionVariable. The Event adds the state
+ *        that the condition is gating as well as the mutex/lock.
+ *
+ *        This Event can be 'interruptible' (even though there is only a single place
+ *        in the code that uses this behavior).
+ *
+ *        This class manages 'spurious returns' from the condition variable.
+ *
+ */
+
+class CEvent
+{
+  bool manualReset;
+  volatile bool signaled;
+  unsigned int numWaits = 0;
+
+  CCriticalSection groupListMutex; // lock for the groups list
+  std::unique_ptr<std::vector<XbmcThreads::CEventGroup*>> groups;
+
+  XbmcThreads::ConditionVariable actualCv;
+  CCriticalSection mutex;
+
+  friend class XbmcThreads::CEventGroup;
+
+  void addGroup(XbmcThreads::CEventGroup* group);
+  void removeGroup(XbmcThreads::CEventGroup* group);
+
+  // helper for the two wait methods
+  inline bool prepReturn()
+  {
+    bool ret = signaled;
+    if (!manualReset && numWaits == 0)
+      signaled = false;
+    return ret;
+  }
+
+  CEvent(const CEvent&) = delete;
+  CEvent& operator=(const CEvent&) = delete;
+
+public:
+  inline CEvent(bool manual = false, bool signaled_ = false)
+    : manualReset(manual), signaled(signaled_)
+  {
+  }
+
+  inline void Reset()
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    signaled = false;
+  }
+  void Set();
+
+  /**
+   * @brief Returns true if Event has been triggered and not reset, false otherwise.
+   *
+   */
+  inline bool Signaled()
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    return signaled;
+  }
+
+  /**
+   * @brief This will wait up to 'duration' for the Event to be
+   *        triggered. The method will return 'true' if the Event
+   *        was triggered. Otherwise it will return false.
+   *
+   */
+  template<typename Rep, typename Period>
+  inline bool Wait(std::chrono::duration<Rep, Period> duration)
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    numWaits++;
+    actualCv.wait(mutex, duration, std::bind(&CEvent::Signaled, this));
+    numWaits--;
+    return prepReturn();
+  }
+
+  /**
+   * @brief This will wait for the Event to be triggered. The method will return
+   *        'true' if the Event was triggered. If it was either interrupted
+   *        it will return false. Otherwise it will return false.
+   *
+   */
+  inline bool Wait()
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    numWaits++;
+    actualCv.wait(mutex, std::bind(&CEvent::Signaled, this));
+    numWaits--;
+    return prepReturn();
+  }
+
+  /**
+   * @brief This is mostly for testing. It allows a thread to make sure there are
+   *        the right amount of other threads waiting.
+   *
+   */
+  inline int getNumWaits()
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    return numWaits;
+  }
+};
+
+namespace XbmcThreads
+{
+/**
+ * @brief  CEventGroup is a means of grouping CEvents to wait on them together.
+ *         It is equivalent to WaitOnMultipleObject that returns when "any" Event
+ *         in the group signaled.
+ *
+ */
+class CEventGroup
+{
+  std::vector<CEvent*> events;
+  CEvent* signaled{};
+  XbmcThreads::ConditionVariable actualCv;
+  CCriticalSection mutex;
+
+  unsigned int numWaits{0};
+
+  // This is ONLY called from CEvent::Set.
+  inline void Set(CEvent* child)
+  {
+    std::unique_lock<CCriticalSection> l(mutex);
+    signaled = child;
+    actualCv.notifyAll();
+  }
+
+  friend class ::CEvent;
+
+  CEventGroup(const CEventGroup&) = delete;
+  CEventGroup& operator=(const CEventGroup&) = delete;
+
+public:
+  /**
+   * @brief Create a CEventGroup from a number of CEvents.
+   *
+   */
+  CEventGroup(std::initializer_list<CEvent*> events);
+
+  ~CEventGroup();
+
+  /**
+   * @brief This will block until any one of the CEvents in the group are
+   *        signaled at which point a pointer to that CEvents will be
+   *        returned.
+   *
+   */
+  CEvent* wait();
+
+  /**
+   * @brief locking is ALWAYS done in this order:
+   *        CEvent::groupListMutex -> CEventGroup::mutex -> CEvent::mutex
+   *
+   *        Notice that this method doesn't grab the CEvent::groupListMutex at all. This
+   *        is fine. It just grabs the CEventGroup::mutex and THEN the individual
+   *
+   */
+  template<typename Rep, typename Period>
+  CEvent* wait(std::chrono::duration<Rep, Period> duration)
+  {
+    std::unique_lock<CCriticalSection> lock(mutex); // grab CEventGroup::mutex
+    numWaits++;
+
+    // ==================================================
+    // This block checks to see if any child events are
+    // signaled and sets 'signaled' to the first one it
+    // finds.
+    // ==================================================
+    signaled = nullptr;
+    for (auto* cur : events)
+    {
+      std::unique_lock<CCriticalSection> lock2(cur->mutex);
+      if (cur->signaled)
+        signaled = cur;
+    }
+    // ==================================================
+
+    if (!signaled)
+    {
+      // both of these release the CEventGroup::mutex
+      if (duration == std::chrono::duration<Rep, Period>::max())
+        actualCv.wait(mutex, [this]() { return signaled != nullptr; });
+      else
+        actualCv.wait(mutex, duration, [this]() { return signaled != nullptr; });
+    } // at this point the CEventGroup::mutex is reacquired
+    numWaits--;
+
+    // signaled should have been set by a call to CEventGroup::Set
+    CEvent* ret = signaled;
+    if (numWaits == 0)
+    {
+      if (signaled)
+        // This acquires and releases the CEvent::mutex. This is fine since the
+        //  CEventGroup::mutex is already being held
+        signaled->Wait(std::chrono::duration<Rep, Period>::zero()); // reset the event if needed
+      signaled = nullptr; // clear the signaled if all the waiters are gone
+    }
+    return ret;
+  }
+
+  /**
+   * @brief This is mostly for testing. It allows a thread to make sure there are
+   *        the right amount of other threads waiting.
+   *
+   */
+  inline int getNumWaits()
+  {
+    std::unique_lock<CCriticalSection> lock(mutex);
+    return numWaits;
+  }
+};
+} // namespace XbmcThreads