sjlj.h

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#ifndef ZTH_CONTEXT_SJLJ_H
#define ZTH_CONTEXT_SJLJ_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 <csetjmp>
#       include <csignal>
 
namespace zth {
 
class Context : public impl::ContextArch<Context> {
        ZTH_CLASS_NEW_DELETE(Context)
public:
        typedef ContextArch<Context> base;
 
        constexpr explicit Context(ContextAttr const& attr) noexcept
                : base(attr)
                , m_env()
        {}
 
private:
#       ifdef ZTH_OS_BAREMETAL
        // As bare metal does not have signals, sigsetjmp and siglongjmp is not necessary.
        typedef jmp_buf jmp_buf_type;
#               define zth_sjlj_setjmp(env)        ::setjmp(env)
#               define zth_sjlj_longjmp(env, val) ::longjmp(env, val)
#       else
        typedef sigjmp_buf jmp_buf_type;
#               define zth_sjlj_setjmp(env)        ::sigsetjmp(env, Config::ContextSignals)
#               define zth_sjlj_longjmp(env, val) ::siglongjmp(env, val)
#       endif
 
public:
        int create() noexcept
        {
                int res = base::create();
                if(res)
                        return res;
 
                if(unlikely(!stack()))
                        // Stackless fiber only saves current context; nothing to do.
                        return 0;
 
                zth_sjlj_setjmp(m_env);
                void** sp_ = sp(stackUsable());
                set_sp(m_env, sp_);
                set_pc(m_env, reinterpret_cast<void*>(&context_trampoline_from_jmp_buf));
                stack_push(sp_, this);
                return 0;
        }
 
        void context_switch(Context& to) noexcept
        {
                context_push_regs();
 
                if(zth_sjlj_setjmp(m_env) == 0) {
                        context_prepare_jmp(to, to.m_env);
                        zth_sjlj_longjmp(to.m_env, 1);
                }
 
                context_pop_regs();
        }
 
private:
        jmp_buf_type m_env;
};
 
} // namespace zth
#endif // __cplusplus
#endif // ZTH_CONTEXT_SJLJ_H