3 files changed, 204 insertions, 0 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index c8bf80372..554d6e253 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -110,6 +110,8 @@ add_library(common STATIC
     common_types.h
     dynamic_library.cpp
     dynamic_library.h
+    fiber.cpp
+    fiber.h
     file_util.cpp
     file_util.h
     hash.h
diff --git a/src/common/fiber.cpp b/src/common/fiber.cpp
new file mode 100644
index 000000000..eb59f1aa9
--- /dev/null
+++ b/src/common/fiber.cpp
@@ -0,0 +1,147 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/fiber.h"
+
+namespace Common {
+
+#ifdef _MSC_VER
+#include <windows.h>
+
+struct Fiber::FiberImpl {
+    LPVOID handle = nullptr;
+};
+
+void Fiber::_start([[maybe_unused]] void* parameter) {
+    guard.lock();
+    if (previous_fiber) {
+        previous_fiber->guard.unlock();
+        previous_fiber = nullptr;
+    }
+    entry_point(start_parameter);
+}
+
+static void __stdcall FiberStartFunc(LPVOID lpFiberParameter)
+{
+   auto fiber = static_cast<Fiber *>(lpFiberParameter);
+   fiber->_start(nullptr);
+}
+
+Fiber::Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter)
+    : guard{}, entry_point{std::move(entry_point_func)}, start_parameter{start_parameter}, previous_fiber{} {
+    impl = std::make_unique<FiberImpl>();
+    impl->handle = CreateFiber(0, &FiberStartFunc, this);
+}
+
+Fiber::Fiber() : guard{}, entry_point{}, start_parameter{}, previous_fiber{} {
+    impl = std::make_unique<FiberImpl>();
+}
+
+Fiber::~Fiber() {
+    // Make sure the Fiber is not being used
+    guard.lock();
+    guard.unlock();
+    DeleteFiber(impl->handle);
+}
+
+void Fiber::Exit() {
+    if (!is_thread_fiber) {
+        return;
+    }
+    ConvertFiberToThread();
+    guard.unlock();
+}
+
+void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) {
+    to->guard.lock();
+    to->previous_fiber = from;
+    SwitchToFiber(to->impl->handle);
+    auto previous_fiber = from->previous_fiber;
+    if (previous_fiber) {
+        previous_fiber->guard.unlock();
+        previous_fiber.reset();
+    }
+}
+
+std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
+    std::shared_ptr<Fiber> fiber = std::shared_ptr<Fiber>{new Fiber()};
+    fiber->guard.lock();
+    fiber->impl->handle = ConvertThreadToFiber(NULL);
+    fiber->is_thread_fiber = true;
+    return fiber;
+}
+
+#else
+
+#include <boost/context/detail/fcontext.hpp>
+
+constexpr std::size_t default_stack_size = 1024 * 1024 * 4; // 4MB
+
+struct Fiber::FiberImpl {
+    boost::context::detail::fcontext_t context;
+    std::array<u8, default_stack_size> stack;
+};
+
+void Fiber::_start(void* parameter) {
+    guard.lock();
+    boost::context::detail::transfer_t* transfer = static_cast<boost::context::detail::transfer_t*>(parameter);
+    if (previous_fiber) {
+        previous_fiber->impl->context = transfer->fctx;
+        previous_fiber->guard.unlock();
+        previous_fiber = nullptr;
+    }
+    entry_point(start_parameter);
+}
+
+static void FiberStartFunc(boost::context::detail::transfer_t transfer)
+{
+   auto fiber = static_cast<Fiber *>(transfer.data);
+   fiber->_start(&transfer);
+}
+
+Fiber::Fiber(std::function<void(void*)>&& entry_point_func, void* start_parameter)
+    : guard{}, entry_point{std::move(entry_point_func)}, start_parameter{start_parameter}, previous_fiber{} {
+    impl = std::make_unique<FiberImpl>();
+    auto start_func = std::bind(&Fiber::start, this);
+    impl->context =
+        boost::context::detail::make_fcontext(impl->stack.data(), impl->stack.size(), &start_func);
+}
+
+Fiber::Fiber() : guard{}, entry_point{}, start_parameter{}, previous_fiber{} {
+    impl = std::make_unique<FiberImpl>();
+}
+
+Fiber::~Fiber() {
+    // Make sure the Fiber is not being used
+    guard.lock();
+    guard.unlock();
+}
+
+void Fiber::Exit() {
+    if (!is_thread_fiber) {
+        return;
+    }
+    guard.unlock();
+}
+
+void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) {
+    to->guard.lock();
+    to->previous_fiber = from;
+    auto transfer = boost::context::detail::jump_fcontext(to->impl.context, nullptr);
+    auto previous_fiber = from->previous_fiber;
+    if (previous_fiber) {
+        previous_fiber->impl->context = transfer.fctx;
+        previous_fiber->guard.unlock();
+        previous_fiber.reset();
+    }
+}
+
+std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
+    std::shared_ptr<Fiber> fiber = std::shared_ptr<Fiber>{new Fiber()};
+    fiber->is_thread_fiber = true;
+    return fiber;
+}
+
+#endif
+} // namespace Common
diff --git a/src/common/fiber.h b/src/common/fiber.h
new file mode 100644
index 000000000..ab44905cf
--- /dev/null
+++ b/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