93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
// Copyright 2020 yuzu Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#pragma once
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#include <functional>
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#include <memory>
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#include "common/common_types.h"
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#include "common/spin_lock.h"
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#if !defined(_WIN32) && !defined(WIN32)
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namespace boost::context::detail {
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struct transfer_t;
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}
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#endif
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namespace Common {
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/**
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* Fiber class
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* a fiber is a userspace thread with it's own context. They can be used to
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* implement coroutines, emulated threading systems and certain asynchronous
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* patterns.
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*
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* This class implements fibers at a low level, thus allowing greater freedom
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* to implement such patterns. This fiber class is 'threadsafe' only one fiber
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* can be running at a time and threads will be locked while trying to yield to
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* a running fiber until it yields. WARNING exchanging two running fibers between
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* threads will cause a deadlock. In order to prevent a deadlock, each thread should
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* have an intermediary fiber, you switch to the intermediary fiber of the current
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* thread and then from it switch to the expected fiber. This way you can exchange
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* 2 fibers within 2 different threads.
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*/
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class Fiber {
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public:
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Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter);
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~Fiber();
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Fiber(const Fiber&) = delete;
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Fiber& operator=(const Fiber&) = delete;
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Fiber(Fiber&&) = default;
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Fiber& operator=(Fiber&&) = default;
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/// Yields control from Fiber 'from' to Fiber 'to'
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/// Fiber 'from' must be the currently running fiber.
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static void YieldTo(std::shared_ptr<Fiber>& from, std::shared_ptr<Fiber>& to);
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[[nodiscard]] static std::shared_ptr<Fiber> ThreadToFiber();
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void SetRewindPoint(std::function<void(void*)>&& rewind_func, void* start_parameter);
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void Rewind();
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/// Only call from main thread's fiber
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void Exit();
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/// Changes the start parameter of the fiber. Has no effect if the fiber already started
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void SetStartParameter(void* new_parameter) {
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start_parameter = new_parameter;
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}
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private:
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Fiber();
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#if defined(_WIN32) || defined(WIN32)
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void OnRewind();
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void Start();
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static void FiberStartFunc(void* fiber_parameter);
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static void RewindStartFunc(void* fiber_parameter);
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#else
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void OnRewind(boost::context::detail::transfer_t& transfer);
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void Start(boost::context::detail::transfer_t& transfer);
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static void FiberStartFunc(boost::context::detail::transfer_t transfer);
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static void RewindStartFunc(boost::context::detail::transfer_t transfer);
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#endif
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struct FiberImpl;
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SpinLock guard{};
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std::function<void(void*)> entry_point;
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std::function<void(void*)> rewind_point;
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void* rewind_parameter{};
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void* start_parameter{};
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std::shared_ptr<Fiber> previous_fiber;
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std::unique_ptr<FiberImpl> impl;
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bool is_thread_fiber{};
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bool released{};
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};
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} // namespace Common
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