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