Common: Implement a basic Fiber class.

src/common/fiber.h

@@ -0,0 +1,55 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <functional>
+#include <memory>
+
+#include "common/common_types.h"
+#include "common/spin_lock.h"
+
+namespace Common {
+
+class Fiber {
+public:
+    Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter);
+    ~Fiber();
+
+    Fiber(const Fiber&) = delete;
+    Fiber& operator=(const Fiber&) = delete;
+
+    Fiber(Fiber&&) = default;
+    Fiber& operator=(Fiber&&) = default;
+
+    /// Yields control from Fiber 'from' to Fiber 'to'
+    /// Fiber 'from' must be the currently running fiber.
+    static void YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to);
+    static std::shared_ptr<Fiber> ThreadToFiber();
+
+    /// Only call from main thread's fiber
+    void Exit();
+
+    /// Used internally but required to be public, Shall not be used
+    void _start(void* parameter);
+
+    /// Changes the start parameter of the fiber. Has no effect if the fiber already started
+    void SetStartParameter(void* new_parameter) {
+        start_parameter = new_parameter;
+    }
+
+private:
+    Fiber();
+
+    struct FiberImpl;
+
+    SpinLock guard;
+    std::function<void(void*)> entry_point;
+    void* start_parameter;
+    std::shared_ptr<Fiber> previous_fiber;
+    std::unique_ptr<FiberImpl> impl;
+    bool is_thread_fiber{};
+};
+
+} // namespace Common