Fix Event implementation

On non-windows platforms this just used a semaphore, which meant that multiple calls to signal() would result in wait() returning multiple times.
minetest · Dec 7, 2015 · 696148e · 696148e · MoNTE48 · Dec 10, 2015
1 parent ea2964f
commit 696148e
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Showing 3 changed files with 121 additions and 13 deletions.
diff --git a/src/threading/CMakeLists.txt b/src/threading/CMakeLists.txt
@@ -1,4 +1,5 @@
 set(JTHREAD_SRCS
+	${CMAKE_CURRENT_SOURCE_DIR}/event.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/mutex.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/thread.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/semaphore.cpp

diff --git a/src/threading/event.cpp b/src/threading/event.cpp
@@ -0,0 +1,95 @@
+/*
+This file is a part of the JThread package, which contains some object-
+oriented thread wrappers for different thread implementations.
+
+Copyright (c) 2000-2006  Jori Liesenborgs (jori.liesenborgs@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+*/
+
+#include "threading/event.h"
+
+#if defined(_WIN32)
+	#ifndef WIN32_LEAN_AND_MEAN
+		#define WIN32_LEAN_AND_MEAN
+	#endif
+	#include <windows.h>
+#endif
+
+
+#if __cplusplus < 201103L
+Event::Event()
+{
+#ifdef _WIN32
+	event = CreateEvent(NULL, false, false, NULL);
+#else
+	pthread_cond_init(&cv, NULL);
+	pthread_mutex_init(&mutex, NULL);
+#endif
+}
+
+Event::~Event()
+{
+#ifdef _WIN32
+	CloseHandle(event);
+#else
+	pthread_cond_destroy(&cv);
+	pthread_mutex_destroy(&mutex);
+#endif
+}
+#endif
+
+
+void Event::wait()
+{
+#if __cplusplus >= 201103L
+	MutexAutoLock lock(mutex);
+	while (!notified) {
+		cv.wait(lock);
+	}
+	notified = false;
+#elif defined(_WIN32)
+	WaitForSingleObject(event, INFINITE);
+#else
+	pthread_mutex_lock(&mutex);
+	while (!notified) {
+		pthread_cond_wait(&cv, &mutex);
+	}
+	notified = false;
+	pthread_mutex_unlock(&mutex);
+#endif
+}
+
+
+void Event::signal()
+{
+#if __cplusplus >= 201103L
+	MutexAutoLock lock(mutex);
+	notified = true;
+	cv.notify_one();
+#elif defined(_WIN32)
+	SetEvent(event);
+#else
+	pthread_mutex_lock(&mutex);
+	notified = true;
+	pthread_cond_signal(&cv);
+	pthread_mutex_unlock(&mutex);
+#endif
+}
+
diff --git a/src/threading/event.h b/src/threading/event.h
@@ -26,30 +26,42 @@ DEALINGS IN THE SOFTWARE.
 #ifndef THREADING_EVENT_H
 #define THREADING_EVENT_H
 
-#ifdef _WIN32
-	#include <windows.h>
+#if __cplusplus >= 201103L
+	#include <condition_variable>
+	#include "threading/mutex.h"
+#elif defined(_WIN32)
+	#include <windef.h>
 #else
-	#include "threading/semaphore.h"
+	#include <pthread.h>
 #endif
 
 
+/** A syncronization primitive that will wake up one waiting thread when signaled.
+ * Calling @c signal() multiple times before a waiting thread has had a chance
+ * to notice the signal will wake only one thread.  Additionally, if no threads
+ * are waiting on the event when it is signaled, the next call to @c wait()
+ * will return (almost) immediately.
+ */
 class Event {
 public:
-#ifdef _WIN32
-	Event() { event = CreateEvent(NULL, false, false, NULL); }
-	~Event() { CloseHandle(event); }
-	void wait() { WaitForSingleObject(event, INFINITE); }
-	void signal() { SetEvent(event); }
-#else
-	void wait() { sem.wait(); }
-	void signal() { sem.post(); }
+#if __cplusplus < 201103L
+	Event();
+	~Event();
 #endif
+	void wait();
+	void signal();
 
 private:
-#ifdef _WIN32
+#if __cplusplus >= 201103L
+	std::condition_variable cv;
+	Mutex mutex;
+	bool notified;
+#elif defined(_WIN32)
 	HANDLE event;
 #else
-	Semaphore sem;
+	pthread_cond_t cv;
+	pthread_mutex_t mutex;
+	bool notified;
 #endif
 };