orb: move SmartLock into global space and use it also for NuttX

src/platforms/px4_sem.hpp

@@ -0,0 +1,68 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2016 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file px4_sem.hpp
+ *
+ * C++ synchronization helpers
+ */
+
+#pragma once
+
+#include "px4_sem.h"
+
+
+/**
+ * @class Smart locking object that uses a semaphore. It automatically
+ * takes the lock when created and releases the lock when the object goes out of
+ * scope. Use like this:
+ *
+ *   px4_sem_t my_lock;
+ *   int ret = px4_sem_init(&my_lock, 0, 1);
+ *   ...
+ *
+ *   {
+ *       SmartLock smart_lock(my_lock);
+ *       //critical section start
+ *       ...
+ *       //critical section end
+ *   }
+ */
+class SmartLock
+{
+public:
+	SmartLock(px4_sem_t &sem) : _sem(sem) { do {} while (px4_sem_wait(&_sem) != 0); }
+	~SmartLock() { px4_sem_post(&_sem); }
+private:
+	px4_sem_t &_sem;
+};