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/*
* Copyright (c) 2023 Balazs Scheidler <balazs.scheidler@axoflow.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* As an additional exemption you are allowed to compile & link against the
* OpenSSL libraries as published by the OpenSSL project. See the file
* COPYING for details.
*
*/
#include "filterx/filterx-weakrefs.h"
#include "filterx/filterx-eval.h"
/*
* Weakrefs can be used to break up circular references between objects
* without having to do expensive loop discovery. Although we are not
* implementing complete weakref support, the interface mimics that, so we
* could eventually implement it.
*
* Weakrefs work as follows:
* - each object can have a combination of hard refs and weak refs
* - the object can be freed when the hard references are gone
* - all weak refs will be cleared (e.g. set to NULL) when the object is freed
*
* This means that if we have circular references between a objects (not
* necessarily two), the circle can be broken by just one weakref in the loop.
*
* Our weakref implementation is limited, as we don't have a GC mechanism.
* We will destroy lingering objects at the end of our current scope and
* weakrefs don't outlive scopes.
*
* With this assumption, our end-of-scope disposal of objects will work like this:
* - we get rid of all weakrefs
* - we get rid of all hardrefs
*
* Which should just get rid of all loops. We currently _do not_ set the
* weakref back to NULL at disposal, since no code is to be executed _after_
* the disposal is done, e.g. the invalidated pointers should not be
* dereferenced.
*/
void
filterx_weakref_set(FilterXWeakRef *self, FilterXObject *object)
{
filterx_eval_store_weak_ref(object);
self->object = object;
}
void
filterx_weakref_clear(FilterXWeakRef *self)
{
/* we do nothing with our ref here as that should be disposed at the end of the scope automatically */
self->object = NULL;
}
/* NOTE: returns a hard reference if the weakref is still valid */
FilterXObject *
filterx_weakref_get(FilterXWeakRef *self)
{
/* deref is now just returning the pointer, we don't have a means to
* validate if it's valid, we just assume it is until our Scope has not
* been terminated yet */
return filterx_object_ref(self->object);
}
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