winfiber.h

Go to the documentation of this file.

#ifndef ZTH_CONTEXT_WINFIBER_H
#define ZTH_CONTEXT_WINFIBER_H
/*
 * Zth (libzth), a cooperative userspace multitasking library.
 * Copyright (C) 2019-2022  Jochem Rutgers
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */
 
#ifndef ZTH_CONTEXT_CONTEXT_H
#       error This file must be included by libzth/context/context.h.
#endif
 
#ifdef __cplusplus
 
#       include <windows.h>
 
namespace zth {
 
class Context : public impl::ContextArch<Context> {
        ZTH_CLASS_NEW_DELETE(Context)
public:
        typedef impl::ContextArch<Context> base;
 
        constexpr explicit Context(ContextAttr const& attr) noexcept
                : base(attr)
                , m_fiber()
        {}
 
        static int init() noexcept
        {
                int res = 0;
                if(ConvertThreadToFiber(nullptr))
                        return 0;
                else if((res = -(int)GetLastError()))
                        return res;
                else
                        return EINVAL;
        }
 
        int initStack(Stack& UNUSED_PAR(stack), Stack& UNUSED_PAR(usable)) noexcept
        {
                // Stack is managed by Windows.
                usable = stack;
                return 0;
        }
 
        void deinitStack(Stack& UNUSED_PAR(stack)) noexcept {}
 
        int stackGuardInit() noexcept
        {
                // There is no stack to guard.
                return 0;
        }
 
        void stackGuardDeinit() noexcept {}
 
        void valgrindRegister() noexcept
        {
                // There is no stack to register.
        }
 
        void valgrindDeregister() noexcept {}
 
        int create() noexcept
        {
                int res = 0;
                if((res = base::create()))
                        return res;
 
                if(unlikely(!stack().size)) {
                        // Stackless fiber only saves current context.
                        if((m_fiber = GetCurrentFiber()))
                                return 0;
                } else if((m_fiber = CreateFiber(
                                   (SIZE_T)Config::DefaultFiberStackSize,
                                   reinterpret_cast<LPFIBER_START_ROUTINE>(&context_entry),
                                   (LPVOID)this))) {
                        zth_dbg(context, "[%s] Created fiber %p", currentWorker().id_str(),
                                m_fiber);
                        return 0;
                }
 
                if((res = -(int)GetLastError()))
                        return res;
                else
                        return EINVAL;
        }
 
        void destroy() noexcept
        {
                if(!m_fiber)
                        return;
 
                // If the current fiber is the one to delete, it is probably not created by us.
                if(likely(m_fiber != GetCurrentFiber())) {
                        zth_dbg(context, "[%s] Delete fiber %p", currentWorker().id_str(), m_fiber);
                        DeleteFiber(m_fiber);
                }
 
                m_fiber = nullptr;
        }
 
        void context_switch(Context& to) noexcept
        {
                zth_assert(to.m_fiber && to.m_fiber != GetCurrentFiber());
                SwitchToFiber(to.m_fiber);
        }
 
private:
        LPVOID m_fiber;
};
 
} // namespace zth
#endif // __cplusplus
#endif // ZTH_CONTEXT_WINFIBER_H