Merge commit 'a2059eea4ad3021eb6a90959eea1edddc57e249d' as 'external/parallel-rdp/parallel-rdp-standalone'

external/parallel-rdp/parallel-rdp-standalone/util/read_write_lock.hpp

@@ -0,0 +1,149 @@
+/* Copyright (c) 2017-2023 Hans-Kristian Arntzen
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <atomic>
+
+#ifdef __SSE2__
+#include <emmintrin.h>
+#endif
+
+namespace Util
+{
+class RWSpinLock
+{
+public:
+	enum { Reader = 2, Writer = 1 };
+	RWSpinLock()
+	{
+		counter.store(0);
+	}
+
+	inline void lock_read()
+	{
+		unsigned v = counter.fetch_add(Reader, std::memory_order_acquire);
+		while ((v & Writer) != 0)
+		{
+#ifdef __SSE2__
+			_mm_pause();
+#endif
+			v = counter.load(std::memory_order_acquire);
+		}
+	}
+
+	inline bool try_lock_read()
+	{
+		unsigned v = counter.fetch_add(Reader, std::memory_order_acquire);
+		if ((v & Writer) != 0)
+		{
+			unlock_read();
+			return false;
+		}
+
+		return true;
+	}
+
+	inline void unlock_read()
+	{
+		counter.fetch_sub(Reader, std::memory_order_release);
+	}
+
+	inline void lock_write()
+	{
+		uint32_t expected = 0;
+		while (!counter.compare_exchange_weak(expected, Writer,
+		                                      std::memory_order_acquire,
+		                                      std::memory_order_relaxed))
+		{
+#ifdef __SSE2__
+			_mm_pause();
+#endif
+			expected = 0;
+		}
+	}
+
+	inline bool try_lock_write()
+	{
+		uint32_t expected = 0;
+		return counter.compare_exchange_strong(expected, Writer,
+		                                       std::memory_order_acquire,
+		                                       std::memory_order_relaxed);
+	}
+
+	inline void unlock_write()
+	{
+		counter.fetch_and(~Writer, std::memory_order_release);
+	}
+
+	inline void promote_reader_to_writer()
+	{
+		uint32_t expected = Reader;
+		if (!counter.compare_exchange_strong(expected, Writer,
+		                                     std::memory_order_acquire,
+		                                     std::memory_order_relaxed))
+		{
+			unlock_read();
+			lock_write();
+		}
+	}
+
+private:
+	std::atomic_uint32_t counter;
+};
+
+class RWSpinLockReadHolder
+{
+public:
+	explicit RWSpinLockReadHolder(RWSpinLock &lock_)
+		: lock(lock_)
+	{
+		lock.lock_read();
+	}
+
+	~RWSpinLockReadHolder()
+	{
+		lock.unlock_read();
+	}
+
+private:
+	RWSpinLock &lock;
+};
+
+class RWSpinLockWriteHolder
+{
+public:
+	explicit RWSpinLockWriteHolder(RWSpinLock &lock_)
+			: lock(lock_)
+	{
+		lock.lock_write();
+	}
+
+	~RWSpinLockWriteHolder()
+	{
+		lock.unlock_write();
+	}
+
+private:
+	RWSpinLock &lock;
+};
+}