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Annotation of Gnu-Mach/util/ref_count.h, revision 1.1.1.1

1.1       root        1: /* 
                      2:  * Copyright (c) 1995-1993 The University of Utah and
                      3:  * the Computer Systems Laboratory at the University of Utah (CSL).
                      4:  * All rights reserved.
                      5:  *
                      6:  * Permission to use, copy, modify and distribute this software is hereby
                      7:  * granted provided that (1) source code retains these copyright, permission,
                      8:  * and disclaimer notices, and (2) redistributions including binaries
                      9:  * reproduce the notices in supporting documentation, and (3) all advertising
                     10:  * materials mentioning features or use of this software display the following
                     11:  * acknowledgement: ``This product includes software developed by the
                     12:  * Computer Systems Laboratory at the University of Utah.''
                     13:  *
                     14:  * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
                     15:  * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
                     16:  * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
                     17:  *
                     18:  * CSL requests users of this software to return to [email protected] any
                     19:  * improvements that they make and grant CSL redistribution rights.
                     20:  *
                     21:  *      Author: Bryan Ford, University of Utah CSL
                     22:  */
                     23: /*
                     24:  *     File:   refcount.h
                     25:  *
                     26:  *     This defines the system-independent atomic reference count data type.
                     27:  *     (This file will often be overridden
                     28:  *     by better machine-dependent implementations.)
                     29:  *
                     30:  */
                     31: 
                     32: #ifndef        _KERN_REF_COUNT_H_
                     33: #define _KERN_REF_COUNT_H_
                     34: 
                     35: #include <mach/macro_help.h>
                     36: 
                     37: #include "simple_lock.h"
                     38: 
                     39: 
                     40: struct ref_count {
                     41:        decl_simple_lock_data(,lock)    /* lock for reference count */
                     42:        int             count;          /* number of references */
                     43: };
                     44: 
                     45: #define ref_count_init(refcount, refs)                 \
                     46:        MACRO_BEGIN                                     \
                     47:                simple_lock_init(&(refcount)->lock);    \
                     48:                ((refcount)->count = (refs));           \
                     49:        MACRO_END
                     50: 
                     51: #define ref_count_take(refcount)                       \
                     52:        MACRO_BEGIN                                     \
                     53:                simple_lock(&(refcount)->lock);         \
                     54:                (refcount)->count++;                    \
                     55:                simple_unlock(&(refcount)->lock);       \
                     56:        MACRO_END
                     57: 
                     58: #define ref_count_drop(refcount, func)                 \
                     59:        MACRO_BEGIN                                     \
                     60:                int new_value;                          \
                     61:                simple_lock(&(refcount)->lock);         \
                     62:                new_value = --(refcount)->count;        \
                     63:                simple_unlock(&(refcount)->lock);       \
                     64:                if (new_value == 0) { func; }           \
                     65:        MACRO_END
                     66: 
                     67: 
                     68: #endif _KERN_REF_COUNT_H_

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