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