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Annotation of OSKit-Mach/kern/refcount.h, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1993,1994 The University of Utah and
                      3:  * the Computer Systems Laboratory (CSL).  All rights reserved.
                      4:  *
                      5:  * Permission to use, copy, modify and distribute this software and its
                      6:  * documentation is hereby granted, provided that both the copyright
                      7:  * notice and this permission notice appear in all copies of the
                      8:  * software, derivative works or modified versions, and any portions
                      9:  * thereof, and that both notices appear in supporting documentation.
                     10:  *
                     11:  * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
                     12:  * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
                     13:  * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
                     14:  *
                     15:  * CSL requests users of this software to return to [email protected] any
                     16:  * improvements that they make and grant CSL redistribution rights.
                     17:  *
                     18:  *      Author: Bryan Ford, University of Utah CSL
                     19:  */
                     20: /*
                     21:  *     File:   refcount.h
                     22:  *
                     23:  *     This defines the system-independent part of the atomic reference count data type.
                     24:  *
                     25:  */
                     26: 
                     27: #ifndef        _KERN_REFCOUNT_H_
                     28: #define _KERN_REFCOUNT_H_
                     29: 
                     30: #include <kern/macro_help.h>
                     31: 
                     32: #include "refcount.h" /*XXX*/
                     33: 
                     34: /* Unless the above include file specified otherwise,
                     35:    use the system-independent (unoptimized) atomic reference counter.  */
                     36: #ifndef MACHINE_REFCOUNT
                     37: 
                     38: #include <kern/lock.h>
                     39: 
                     40: struct RefCount {
                     41:        decl_simple_lock_data(,lock)    /* lock for reference count */
                     42:        int             ref_count;      /* number of references */
                     43: };
                     44: typedef struct RefCount RefCount;
                     45: 
                     46: #define refcount_init(refcount, refs)                  \
                     47:        MACRO_BEGIN                                     \
                     48:                simple_lock_init(&(refcount)->lock);    \
                     49:                ((refcount)->ref_count = (refs));       \
                     50:        MACRO_END
                     51: 
                     52: #define refcount_take(refcount)                                \
                     53:        MACRO_BEGIN                                     \
                     54:                simple_lock(&(refcount)->lock);         \
                     55:                (refcount)->ref_count++;                \
                     56:                simple_unlock(&(refcount)->lock);       \
                     57:        MACRO_END
                     58: 
                     59: #define refcount_drop(refcount, func)                  \
                     60:        MACRO_BEGIN                                     \
                     61:                int new_value;                          \
                     62:                simple_lock(&(refcount)->lock);         \
                     63:                new_value = --(refcount)->ref_count;    \
                     64:                simple_unlock(&(refcount)->lock);       \
                     65:                if (new_value == 0) { func; }           \
                     66:        MACRO_END
                     67: 
                     68: #endif
                     69: 
                     70: #endif _KERN_REFCOUNT_H_

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