Introduce AsioConditionVariable

lib/base/io-engine.cpp

@@ -143,6 +143,30 @@ void AsioDualEvent::WaitForClear(boost::asio::yield_context yc)
 	m_IsFalse.Wait(std::move(yc));
 }
 
+AsioConditionVariable::AsioConditionVariable(boost::asio::io_context& io)
+	: m_Timer(io)
+{
+	m_Timer.expires_at(boost::posix_time::pos_infin);
+}
+
+void AsioConditionVariable::Wait(boost::asio::yield_context yc)
+{
+	boost::system::error_code ec;
+	m_Timer.async_wait(yc[ec]);
+}
+
+bool AsioConditionVariable::NotifyOne()
+{
+	boost::system::error_code ec;
+	return m_Timer.cancel_one(ec);
+}
+
+size_t AsioConditionVariable::NotifyAll()
+{
+	boost::system::error_code ec;
+	return m_Timer.cancel(ec);
+}
+
 /**
  * Cancels any pending timeout callback.
  *

lib/base/io-engine.hpp

@@ -55,6 +55,24 @@ private:
 	bool m_Done;
 };
 
+/**
+ * Condition variable which doesn't block I/O threads
+ *
+ * @ingroup base
+ */
+class AsioConditionVariable
+{
+public:
+	AsioConditionVariable(boost::asio::io_context& io);
+
+	void Wait(boost::asio::yield_context yc);
+	bool NotifyOne();
+	size_t NotifyAll();
+
+private:
+	boost::asio::deadline_timer m_Timer;
+};
+
 /**
  * Async I/O engine
  *