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/* $Id: objectslist.h $ */
/** @file
*
* List of COM objects
*/
/*
* Copyright (C) 2009-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* SPDX-License-Identifier: GPL-3.0-only
*/
#ifndef MAIN_INCLUDED_objectslist_h
#define MAIN_INCLUDED_objectslist_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif
#include <list>
#include <VBox/com/ptr.h>
/**
* Implements a "flat" objects list with a lock. Since each such list
* has its own lock it is not a good idea to implement trees with this.
*
* ObjectList<T> is designed to behave as if it were a std::list of
* COM pointers of class T; in other words,
* ObjectList<Medium> behaves like std::list< ComObjPtr<Medium> > but
* it's less typing. Iterators, front(), size(), begin() and end()
* are implemented.
*
* In addition it automatically includes an RWLockHandle which can be
* accessed with getLockHandle().
*
* If you need the raw std::list for some reason you can access it with
* getList().
*
* The destructor automatically calls uninit() on every contained
* COM object. If this is not desired, clear the member list before
* deleting the list object.
*/
template<typename T>
class ObjectsList
{
public:
typedef ComObjPtr<T> MyType;
typedef std::list<MyType> MyList;
typedef typename MyList::iterator iterator;
typedef typename MyList::const_iterator const_iterator;
// typename is necessary to disambiguate "::iterator" in templates; see
// the "this might hurt your head" part in
// http://www.parashift.com/c++-faq-lite/templates.html#faq-35.18
ObjectsList(RWLockHandle &lockHandle)
: m_lock(lockHandle)
{ }
~ObjectsList()
{
uninitAll();
}
private:
// prohibit copying and assignment
ObjectsList(const ObjectsList &d);
ObjectsList& operator=(const ObjectsList &d);
public:
/**
* Returns the lock handle which protects this list, for use with
* AutoReadLock or AutoWriteLock.
*/
RWLockHandle& getLockHandle()
{
return m_lock;
}
/**
* Calls m_ll.push_back(p) with locking.
* @param p
*/
void addChild(MyType p)
{
AutoWriteLock al(m_lock COMMA_LOCKVAL_SRC_POS);
m_ll.push_back(p);
}
/**
* Calls m_ll.remove(p) with locking. Does NOT call uninit()
* on the contained object.
* @param p
*/
void removeChild(MyType p)
{
AutoWriteLock al(m_lock COMMA_LOCKVAL_SRC_POS);
m_ll.remove(p);
}
/**
* Appends all objects from another list to the member list.
* Locks the other list for reading but does not lock "this"
* (because it might be on the caller's stack and needs no
* locking).
* @param ll
*/
void appendOtherList(ObjectsList<T> &ll)
{
AutoReadLock alr(ll.getLockHandle() COMMA_LOCKVAL_SRC_POS);
for (const_iterator it = ll.begin();
it != ll.end();
++it)
{
m_ll.push_back(*it);
}
}
/**
* Calls uninit() on every COM object on the list and then
* clears the list, with locking.
*/
void uninitAll()
{
/* The implementation differs from the high level description, because
* it isn't safe to hold any locks when invoking uninit() methods. It
* leads to incorrect lock order (first lock, then the Caller related
* event semaphore) and thus deadlocks. Dropping the lock is vital,
* and means we can't rely on iterators while not holding the lock. */
AutoWriteLock al(m_lock COMMA_LOCKVAL_SRC_POS);
while (!m_ll.empty())
{
/* Need a copy of the element, have to delete the entry before
* dropping the lock, otherwise someone else might mess with the
* list in the mean time, leading to erratic behavior. */
MyType q = m_ll.front();
m_ll.pop_front();
al.release();
q->uninit();
al.acquire();
}
}
/**
* Returns the no. of objects on the list (std::list compatibility)
* with locking.
*/
size_t size()
{
AutoReadLock al(m_lock COMMA_LOCKVAL_SRC_POS);
return m_ll.size();
}
/**
* Returns a raw pointer to the member list of objects.
* Does not lock!
* @return
*/
MyList& getList()
{
return m_ll;
}
/**
* Returns the first object on the list (std::list compatibility)
* with locking.
*/
MyType front()
{
AutoReadLock al(m_lock COMMA_LOCKVAL_SRC_POS);
return m_ll.front();
}
/**
* Returns the begin iterator from the list (std::list compatibility).
* Does not lock!
* @return
*/
iterator begin()
{
return m_ll.begin();
}
/**
* Returns the end iterator from the list (std::list compatibility).
* Does not lock!
*/
iterator end()
{
return m_ll.end();
}
void insert(iterator it, MyType &p)
{
m_ll.insert(it, p);
}
void erase(iterator it)
{
m_ll.erase(it);
}
private:
MyList m_ll;
RWLockHandle &m_lock;
};
#endif /* !MAIN_INCLUDED_objectslist_h */
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