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/* Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
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, either version 3 of the License, or
(at your option) any later version.
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 <http://www.gnu.org/licenses/>.
*/
/*!
* \file ref.h
*
* \author Marek Vavrusa <marek.vavrusa@nic.cz>
*
* \brief Atomic reference counting structures.
*
* Reference counting allows implicit sharing of objects
* between threads with custom destructor functions.
*
* \addtogroup common_lib
* @{
*/
#ifndef _KNOTD_REF_H_
#define _KNOTD_REF_H_
#include <stddef.h>
struct ref_t;
/*! \brief Prototype for object destructor callback. */
typedef void (*ref_destructor_t)(struct ref_t * p);
/*!
* \brief Structure for reference counting.
*
* Size equals to two sizes of pointer size.
* Structure may be embedded to the structures which
* we want to use for reference counting.
*
* \code
* struct mystruct {
* ref_t ref;
* int mydata;
* char *mystr;
* }
* \endcode
*/
typedef struct ref_t {
size_t count; /*! \brief Reference counter. */
ref_destructor_t dtor; /*! \brief Object destructor function. */
} ref_t;
/*!
* \brief Initialize reference counter.
*
* Set reference counter to 0 and initialize destructor callback.
*
* \param p Reference-counted object.
* \param dtor Destructor function.
*/
void ref_init(ref_t *p, ref_destructor_t dtor);
/*!
* \brief Mark object as used by the caller.
*
* Reference counter will be incremented.
*
* \param p Reference-counted object.
*/
void ref_retain(ref_t *p);
/*!
* \brief Marks object as unused by the caller.
*
* Reference counter will be decremented.
*
* \param p Reference-counted object.
*/
void ref_release(ref_t *p);
#endif /* _KNOTD_REF_H_ */
/*! @} */
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