mirror of
https://github.com/OpenVPN/openvpn3.git
synced 2024-09-20 20:13:05 +02:00
4add0c9bdc
with move-only semantics.
125 lines
2.9 KiB
C++
125 lines
2.9 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2015 OpenVPN Technologies, Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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// High-performance functor with move-only semantics.
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#ifndef OPENVPN_COMMON_FUNCTION_H
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#define OPENVPN_COMMON_FUNCTION_H
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#include <new>
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#include <utility>
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namespace openvpn {
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template <typename F>
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class Function;
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template <typename R, typename ... A>
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class Function<R(A...)>
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{
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public:
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static constexpr size_t N = 3; // max size of functor in machine words
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template <typename T>
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Function(T&& functor) noexcept
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{
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static_assert(sizeof(Intern<T>) <= sizeof(data), "Functor too large");
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setup_methods<T>();
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new (data) Intern<T>(std::move(functor));
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}
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Function(Function&& f) noexcept
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{
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methods = f.methods;
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methods->move(data, f.data);
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}
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~Function()
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{
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methods->destruct(data);
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}
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R operator()(A... args)
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{
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return methods->invoke(data, args...);
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}
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private:
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struct Methods
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{
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R (*invoke)(void *, A...);
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void (*move)(void *, void *);
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void (*destruct)(void *);
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};
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template <typename T>
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void setup_methods()
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{
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static const struct Methods m = {
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&Intern<T>::invoke,
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&Intern<T>::move,
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&Intern<T>::destruct,
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};
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methods = &m;
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}
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template <typename T>
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class Intern
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{
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public:
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Intern(Intern&& obj) noexcept
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: functor_(std::move(obj.functor_))
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{
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}
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Intern(T&& functor) noexcept
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: functor_(std::move(functor))
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{
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}
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static R invoke(void *ptr, A... args)
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{
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Intern* self = reinterpret_cast<Intern<T>*>(ptr);
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return self->functor_(args...);
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}
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static void move(void *dest, void *src)
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{
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Intern* s = reinterpret_cast<Intern<T>*>(src);
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new (dest) Intern(std::move(*s));
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}
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static void destruct(void *ptr)
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{
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Intern* self = reinterpret_cast<Intern<T>*>(ptr);
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self->~Intern();
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}
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private:
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T functor_;
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};
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const Methods* methods;
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void* data[N];
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};
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}
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#endif
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