uORB: add bitset for faster orb_exists check and remove uORB::Subscription lazy subscribe hack/optimization

- add PX4 bitset and atomic_bitset with testing
 - add uORB::Subscription constructor to take ORB_ID enum
 - move orb test messages into msg/

platforms/common/include/px4_platform_common/atomic.h

@@ -72,7 +72,7 @@ public:
 	static_assert(__atomic_always_lock_free(sizeof(T), 0), "atomic is not lock-free for the given type T");
 #endif
 
-
+	atomic() = default;
 	explicit atomic(T value) : _value(value) {}
 
 	/**
@@ -175,9 +175,9 @@ private:
 #ifdef __PX4_QURT
 	// It seems that __atomic_store  and __atomic_load are not supported on Qurt,
 	// so the best that we can do is to use volatile.
-	volatile T _value;
+	volatile T _value{};
 #else
-	T _value;
+	T _value {};
 #endif
 };
 

platforms/common/include/px4_platform_common/atomic_bitset.h

@@ -0,0 +1,95 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2020 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.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include "atomic.h"
+
+namespace px4
+{
+
+template <size_t N>
+class AtomicBitset
+{
+public:
+
+	AtomicBitset() = default;
+
+	size_t count() const
+	{
+		size_t total = 0;
+
+		for (const auto &x : _data) {
+			uint32_t y = x.load();
+
+			while (y) {
+				total += y & 1;
+				y >>= 1;
+			}
+		}
+
+		return total;
+	}
+
+	size_t size() const { return N; }
+
+	bool operator[](size_t position) const
+	{
+		return _data[array_index(position)].load() & element_mask(position);
+	}
+
+	void set(size_t pos, bool val = true)
+	{
+		const uint32_t bitmask = element_mask(pos);
+
+		if (val) {
+			_data[array_index(pos)].fetch_or(bitmask);
+
+		} else {
+			_data[array_index(pos)].fetch_and(~bitmask);
+		}
+	}
+
+private:
+	static constexpr uint8_t BITS_PER_ELEMENT = 32;
+	static constexpr size_t ARRAY_SIZE = ((N % BITS_PER_ELEMENT) == 0) ? (N / BITS_PER_ELEMENT) :
+					     (N / BITS_PER_ELEMENT + 1);
+	static constexpr size_t ALLOCATED_BITS = ARRAY_SIZE * BITS_PER_ELEMENT;
+
+	size_t array_index(size_t position) const { return position / BITS_PER_ELEMENT; }
+	uint32_t element_mask(size_t position) const { return (1 << (position % BITS_PER_ELEMENT)); }
+
+	px4::atomic<uint32_t> _data[ARRAY_SIZE];
+};
+
+} // namespace px4