Add a high-performance spin mutex class.

src/README.md

@@ -10,4 +10,8 @@ A quick circular buffer template class.
 
 ## Onigmo
 
-An improved version based on Onigmo 5.13.5. In particular, **the addition of iterator makes it possible to match gap buffer or nonadjacent memory blocks.** Please refer to the sample files for how to use.
+An improved version based on Onigmo 5.13.5. In particular, **the addition of iterator makes it possible to match gap buffer or nonadjacent memory blocks.** Please refer to the sample files for how to use.
+
+## Spin.h
+
+A high-performance spin mutex and locker.

src/Spin.h

@@ -0,0 +1,79 @@
+ /*
+ * Copyright 2020, WindTerm.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SPIN_H
+#define SPIN_H
+
+#pragma once
+
+#include <atomic>
+#include <thread>
+
+class SpinMutex {
+public:
+	SpinMutex() {
+		unlock();
+	}
+
+	void yield(size_t nCount) {
+		if (nCount < 2) {
+		} else if (nCount < 16) {
+			std::this_thread::yield();
+		} else if (nCount < 32) {
+			std::this_thread::sleep_for(std::chrono::nanoseconds(100));
+		} else {
+			std::this_thread::sleep_for(std::chrono::microseconds(10));
+		}
+	}
+
+	void lock() {
+		for (size_t i = 0; !try_lock(); i++) {
+			yield(i);
+		}
+	}
+
+	void unlock() {
+		flag.clear(std::memory_order_release);
+	}
+
+	bool try_lock() {
+		return flag.test_and_set(std::memory_order_acquire) == false;
+	}
+
+private:
+	SpinMutex(const SpinMutex &) = delete;
+	SpinMutex &operator=(const SpinMutex &) = delete;
+
+	std::atomic_flag flag;
+};
+
+template <typename LockType>
+class ThreadLocker {
+public:
+	ThreadLocker(LockType& m_, bool bLock_ = true) : m(m_), bLock(bLock_) {
+		if (bLock) m.lock();
+	}
+
+	~ThreadLocker() {
+		if (bLock) m.unlock();
+	}
+
+private:
+	LockType& m;
+	bool bLock;
+};
+
+#endif // SPIN_H