mirror of
https://github.com/matrix-construct/construct
synced 2024-10-30 10:28:55 +01:00
102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_UTIL_LIFE_GUARD_H
|
|
|
|
namespace ircd::util
|
|
{
|
|
// Convenience functions for types shared_from_this
|
|
template<class T> std::shared_ptr<const T> shared_from(const T &t);
|
|
template<class T> std::shared_ptr<T> shared_from(T &t);
|
|
template<class T> std::weak_ptr<const T> weak_from(const T &t);
|
|
template<class T> std::weak_ptr<T> weak_from(T &t);
|
|
|
|
template<class T> struct life_guard;
|
|
}
|
|
|
|
/// life_guard is a convenience which takes advantage of std::enable_shared_from_this<T>.
|
|
/// The life_guard glorifies the constructor of an std::shared_ptr<T> by accepting
|
|
/// std::weak_ptr<T> and T& itself all with proper semantics. Once construction is
|
|
/// successful, the user holds it for the duration of the scope ensuring T& survives
|
|
/// context interleaving without being destructed.
|
|
///
|
|
/// Use the life_guard to keep an object alive within a function running in a context.
|
|
///
|
|
/// Example:
|
|
///
|
|
/// void foo(client &c)
|
|
/// {
|
|
/// const life_guard<client> lg(c);
|
|
///
|
|
/// c.call(); // This call was always safe with or w/o life_guard.
|
|
/// ctx::wait(); // The context has now yielded and another context might destroy client &c
|
|
/// c.call(); // The context continues and this would have made a call on a dead c.
|
|
/// }
|
|
///
|
|
template<class T>
|
|
struct ircd::util::life_guard
|
|
:std::shared_ptr<T>
|
|
{
|
|
// This constructor is used when the templated type inherits from std::enable_shared_from_this<>
|
|
template<class SFINAE = T>
|
|
life_guard(T &t,
|
|
typename std::enable_if<is_shared_from_this<SFINAE>(), void>::type * = 0)
|
|
:std::shared_ptr<T>(shared_from(t))
|
|
{}
|
|
|
|
// This constructor uses our convention for forward declaring objects that internally
|
|
// inherit from std::enable_shared_from_this<>. Our convention is to provide:
|
|
//
|
|
// std::shared_ptr<T> shared_from(T &c);
|
|
//
|
|
template<class SFINAE = T>
|
|
life_guard(T &t,
|
|
typename std::enable_if<!is_shared_from_this<SFINAE>(), void>::type * = 0)
|
|
:std::shared_ptr<T>(shared_from(t))
|
|
{}
|
|
|
|
// This constructor is used with a weak_ptr of the type. This throws an exception
|
|
// to abort the scope when the object already died before being able to guard at all.
|
|
life_guard(const std::weak_ptr<T> &wp)
|
|
:std::shared_ptr<T>(wp.lock())
|
|
{
|
|
if(wp.expired())
|
|
throw std::bad_weak_ptr();
|
|
}
|
|
};
|
|
|
|
template<class T>
|
|
std::weak_ptr<T>
|
|
ircd::util::weak_from(T &t)
|
|
{
|
|
return shared_from(t);
|
|
};
|
|
|
|
template<class T>
|
|
std::weak_ptr<const T>
|
|
ircd::util::weak_from(const T &t)
|
|
{
|
|
return shared_from(t);
|
|
};
|
|
|
|
template<class T>
|
|
std::shared_ptr<T>
|
|
ircd::util::shared_from(T &t)
|
|
{
|
|
return dynamic_pointer_cast<T>(t.shared_from_this());
|
|
};
|
|
|
|
template<class T>
|
|
std::shared_ptr<const T>
|
|
ircd::util::shared_from(const T &t)
|
|
{
|
|
return dynamic_pointer_cast<const T>(t.shared_from_this());
|
|
};
|