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// 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"
#if !defined(_WIN32) && !defined(WIN32)
namespace boost::context::detail {
struct transfer_t;
}
#endif
namespace Common {
/**
* Fiber class
* a fiber is a userspace thread with it's own context. They can be used to
* implement coroutines, emulated threading systems and certain asynchronous
* patterns.
*
* This class implements fibers at a low level, thus allowing greater freedom
* to implement such patterns. This fiber class is 'threadsafe' only one fiber
* can be running at a time and threads will be locked while trying to yield to
* a running fiber until it yields. WARNING exchanging two running fibers between
* threads will cause a deadlock. In order to prevent a deadlock, each thread should
* have an intermediary fiber, you switch to the intermediary fiber of the current
* thread and then from it switch to the expected fiber. This way you can exchange
* 2 fibers within 2 different threads.
*/
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&&) = delete;
Fiber& operator=(Fiber&&) = delete;
/// 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);
[[nodiscard]] static std::shared_ptr<Fiber> ThreadToFiber();
void SetRewindPoint(std::function<void(void*)>&& rewind_func, void* start_parameter);
void Rewind();
/// Only call from main thread's fiber
void Exit();
/// 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();
#if defined(_WIN32) || defined(WIN32)
void OnRewind();
void Start();
static void FiberStartFunc(void* fiber_parameter);
static void RewindStartFunc(void* fiber_parameter);
#else
void OnRewind(boost::context::detail::transfer_t& transfer);
void Start(boost::context::detail::transfer_t& transfer);
static void FiberStartFunc(boost::context::detail::transfer_t transfer);
static void RewindStartFunc(boost::context::detail::transfer_t transfer);
#endif
struct FiberImpl;
SpinLock guard{};
std::function<void(void*)> entry_point;
std::function<void(void*)> rewind_point;
void* rewind_parameter{};
void* start_parameter{};
std::shared_ptr<Fiber> previous_fiber;
std::unique_ptr<FiberImpl> impl;
bool is_thread_fiber{};
bool released{};
};
} // namespace Common
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