ircd::util: Add instance_multimap.

include/ircd/util/instance_multimap.h

@@ -0,0 +1,119 @@
+// 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_MULTIMAP_H
+
+namespace ircd::util
+{
+	template<class K, class T> struct instance_multimap;
+}
+
+/// See instance_multimap for purpose and overview.
+template<class K,
+         class T>
+struct ircd::util::instance_multimap
+{
+	static std::multimap<K, T *> map;
+
+  protected:
+	typename decltype(map)::iterator it;
+
+	instance_multimap(const typename decltype(map)::const_iterator &hint, K&& key);
+	instance_multimap(K&& key);
+	instance_multimap(instance_multimap &&) noexcept;
+	instance_multimap(const instance_multimap &);
+	instance_multimap &operator=(instance_multimap &&) noexcept;
+	instance_multimap &operator=(const instance_multimap &);
+	~instance_multimap() noexcept;
+};
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T>::instance_multimap(K&& key)
+:it
+{
+	map.emplace(std::forward<K>(key), static_cast<T *>(this))
+}
+{}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T>::instance_multimap(const typename decltype(map)::const_iterator &hint,
+                                                       K&& key)
+:it
+{
+	map.emplace_hint(hint, std::forward<K>(key), static_cast<T *>(this))
+}
+{}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T>::instance_multimap(instance_multimap &&other)
+noexcept
+:it
+{
+	std::move(other.it)
+}
+{
+	if(it != end(map))
+	{
+		it->second = static_cast<T *>(this);
+		other.it = end(map);
+	}
+}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T>::instance_multimap(const instance_multimap &other)
+:it
+{
+	other.it != end(map)?
+		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
+		end(map)
+}
+{}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T> &
+ircd::util::instance_multimap<K, T>::operator=(instance_multimap &&other)
+noexcept
+{
+	this->~instance_multimap();
+	it = std::move(other.it);
+	if(it != end(map))
+		it->second = static_cast<T *>(this);
+
+	other.it = end(map);
+	return *this;
+}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T> &
+ircd::util::instance_multimap<K, T>::operator=(const instance_multimap &other)
+{
+	this->~instance_multimap();
+	it = other.it != end(map)?
+		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
+		end(map);
+
+	return *this;
+}
+
+template<class K,
+         class T>
+ircd::util::instance_multimap<K, T>::~instance_multimap()
+noexcept
+{
+	if(it != end(map))
+		map.erase(it);
+}

include/ircd/util/util.h

@@ -39,6 +39,7 @@ namespace ircd
 #include "va_rtti.h"
 #include "unique_iterator.h"
 #include "instance_list.h"
+#include "instance_multimap.h"
 #include "bswap.h"
 #include "tuple.h"
 #include "timer.h"