contrib/bind-9.2.4rc7/lib/isc/include/isc/refcount.h

   1 /*
   2  * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (C) 2001, 2003  Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  10  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  11  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  13  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  14  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  15  * PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 /* $Id: refcount.h,v 1.3.2.5 2004/04/14 05:20:19 marka Exp $ */
  19
  20 #ifndef ISC_REFCOUNT_H
  21 #define ISC_REFCOUNT_H 1
  22
  23 #include <isc/lang.h>
  24 #include <isc/mutex.h>
  25 #include <isc/platform.h>
  26 #include <isc/types.h>
  27 #include <isc/util.h>
  28
  29 /*
  30  * Implements a locked reference counter.  These functions may actually be
  31  * implemented using macros, and implementations of these macros are below.
  32  * The isc_refcount_t type should not be accessed directly, as its contents
  33  * depend on the implementation.
  34  */
  35
  36 ISC_LANG_BEGINDECLS
  37
  38 /*
  39  * Function prototypes
  40  */
  41
  42 /*
  43  * void
  44  * isc_refcount_init(isc_refcount_t *ref, unsigned int n);
  45  *
  46  * Initialize the reference counter.  There will be 'n' initial references.
  47  *
  48  * Requires:
  49  *      ref != NULL
  50  */
  51
  52 /*
  53  * void
  54  * isc_refcount_destroy(isc_refcount_t *ref);
  55  *
  56  * Destroys a reference counter.
  57  *
  58  * Requires:
  59  *      ref != NULL
  60  *      The number of references is 0.
  61  */
  62
  63 /*
  64  * void
  65  * isc_refcount_increment(isc_refcount_t *ref, unsigned int *targetp);
  66  *
  67  * Increments the reference count, returning the new value in targetp if it's
  68  * not NULL.
  69  *
  70  * Requires:
  71  *      ref != NULL.
  72  */
  73
  74 /*
  75  * void
  76  * isc_refcount_decrement(isc_refcount_t *ref, unsigned int *targetp);
  77  *
  78  * Decrements the reference count,  returning the new value in targetp if it's
  79  * not NULL.
  80  *
  81  * Requires:
  82  *      ref != NULL.
  83  */
  84
  85
  86 /*
  87  * Sample implementations
  88  */
  89 #ifdef ISC_PLATFORM_USETHREADS
  90
  91 typedef struct isc_refcount {
  92         int refs;
  93         isc_mutex_t lock;
  94 } isc_refcount_t;
  95
  96 #define isc_refcount_init(rp, n)                        \
  97         do {                                            \
  98                 isc_result_t _r;                        \
  99                 (rp)->refs = (n);                       \
 100                 _r = isc_mutex_init(&(rp)->lock);       \
 101                 RUNTIME_CHECK(_r == ISC_R_SUCCESS);     \
 102         } while (0)
 103
 104 #define isc_refcount_destroy(rp)                        \
 105         do {                                            \
 106                 REQUIRE((rp)->refs == 0);               \
 107                 DESTROYLOCK(&(rp)->lock);               \
 108         } while (0)
 109
 110 #define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
 111
 112 #define isc_refcount_increment(rp, tp)                          \
 113         do {                                                    \
 114                 unsigned int *_tmp = (unsigned int *)(tp);      \
 115                 LOCK(&(rp)->lock);                              \
 116                 REQUIRE((rp)->refs > 0);                        \
 117                 ++((rp)->refs);                                 \
 118                 if (_tmp != NULL)                               \
 119                         *_tmp = ((rp)->refs);                   \
 120                 UNLOCK(&(rp)->lock);                            \
 121         } while (0)
 122
 123 #define isc_refcount_decrement(rp, tp)                          \
 124         do {                                                    \
 125                 unsigned int *_tmp = (unsigned int *)(tp);      \
 126                 LOCK(&(rp)->lock);                              \
 127                 REQUIRE((rp)->refs > 0);                        \
 128                 --((rp)->refs);                                 \
 129                 if (_tmp != NULL)                               \
 130                         *_tmp = ((rp)->refs);                   \
 131                 UNLOCK(&(rp)->lock);                            \
 132         } while (0)
 133
 134 #else
 135
 136 typedef struct isc_refcount {
 137         int refs;
 138 } isc_refcount_t;
 139
 140 #define isc_refcount_init(rp, n) ((rp)->refs = (n))
 141 #define isc_refcount_destroy(rp) (REQUIRE((rp)->refs == 0))
 142 #define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
 143
 144 #define isc_refcount_increment(rp, tp)                                  \
 145         do {                                                            \
 146                 unsigned int *_tmp = (unsigned int *)(tp);              \
 147                 int _n = ++(rp)->refs;                                  \
 148                 if (_tmp != NULL)                                       \
 149                         *_tmp = _n;                                     \
 150         } while (0)
 151
 152 #define isc_refcount_decrement(rp, tp)                                  \
 153         do {                                                            \
 154                 unsigned int *_tmp = (unsigned int *)(tp);              \
 155                 int _n = --(rp)->refs;                                  \
 156                 if (_tmp != NULL)                                       \
 157                         *_tmp = _n;                                     \
 158         } while (0)
 159
 160 #endif
 161
 162 ISC_LANG_ENDDECLS
 163
 164 #endif /* ISC_REFCOUNT_H */