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construct/include/ircd/util/instance_list.h

86 lines
2.4 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_INSTANCE_LIST_H
namespace ircd::util
{
template<class T> struct instance_list;
}
/// The instance_list pattern is where every instance of a class registers
/// itself in a static list of all instances and removes itself on dtor.
/// IRCd Ex. All clients use instance_list so all clients can be listed for
/// an administrator or be interrupted and disconnected on server shutdown.
///
/// `struct myobj : ircd::instance_list<myobj> {};`
///
/// * The creator of the class no longer has to manually specify what is
/// defined here using unique_iterator; however, one still must provide
/// linkage for the static list.
///
/// * The container pointer used by unique_iterator is eliminated here
/// because of the static list.
///
template<class T>
struct ircd::util::instance_list
{
static std::list<T *> list;
protected:
typename decltype(list)::iterator it;
instance_list();
instance_list(instance_list &&);
instance_list(const instance_list &);
instance_list &operator=(instance_list &&);
instance_list &operator=(const instance_list &);
~instance_list() noexcept;
};
template<class T>
ircd::util::instance_list<T>::instance_list()
:it{list.emplace(end(list), static_cast<T *>(this))}
{}
template<class T>
ircd::util::instance_list<T>::instance_list(instance_list &&other)
:it{list.emplace(end(list), static_cast<T *>(this))}
{}
template<class T>
ircd::util::instance_list<T>::instance_list(const instance_list &other)
:it{list.emplace(end(list), static_cast<T *>(this))}
{}
template<class T>
ircd::util::instance_list<T> &
ircd::util::instance_list<T>::operator=(instance_list &&other)
{
assert(it != end(list));
return *this;
}
template<class T>
ircd::util::instance_list<T> &
ircd::util::instance_list<T>::operator=(const instance_list &other)
{
assert(it != end(list));
return *this;
}
template<class T>
ircd::util::instance_list<T>::~instance_list()
noexcept
{
assert(it != end(list));
list.erase(it);
}