1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
/** BEGIN COPYRIGHT BLOCK
* This Program is free software; you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation; version 2 of the License.
*
* This Program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with
* this Program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place, Suite 330, Boston, MA 02111-1307 USA.
*
* In addition, as a special exception, Red Hat, Inc. gives You the additional
* right to link the code of this Program with code not covered under the GNU
* General Public License ("Non-GPL Code") and to distribute linked combinations
* including the two, subject to the limitations in this paragraph. Non-GPL Code
* permitted under this exception must only link to the code of this Program
* through those well defined interfaces identified in the file named EXCEPTION
* found in the source code files (the "Approved Interfaces"). The files of
* Non-GPL Code may instantiate templates or use macros or inline functions from
* the Approved Interfaces without causing the resulting work to be covered by
* the GNU General Public License. Only Red Hat, Inc. may make changes or
* additions to the list of Approved Interfaces. You must obey the GNU General
* Public License in all respects for all of the Program code and other code used
* in conjunction with the Program except the Non-GPL Code covered by this
* exception. If you modify this file, you may extend this exception to your
* version of the file, but you are not obligated to do so. If you do not wish to
* provide this exception without modification, you must delete this exception
* statement from your version and license this file solely under the GPL without
* exception.
*
*
* Copyright (C) 2001 Sun Microsystems, Inc. Used by permission.
* Copyright (C) 2005 Red Hat, Inc.
* All rights reserved.
* END COPYRIGHT BLOCK **/
/* Implementation note:
PR_AtomicIncrement and PR_AtomicDecrement both return a value whose
sign is the same sign (or zero) as the variable *after* it was updated.
They do not return the previous value.
*/
#include "slapi-plugin.h"
#include "slapi-private.h"
typedef struct object
{
PRInt32 refcnt; /* reference count for the object */
FNFree destructor; /* Destructor for the object */
void *data; /* pointer to actual node data */
} object;
/*
* Create a new object.
* The object is created with refcnt set to 1. The caller implicitly gets
* a reference to the object, to prevent a race condition where the object
* is destroyed immediately after contruction.
* The provided destructor function will be called when all references to
* the object have been released.
*
* Returns a pointer to the new object.
*/
Object *
object_new(void *user_data, FNFree destructor)
{
Object *o;
o = (object *)slapi_ch_malloc(sizeof(object));
o->refcnt = 1;
o->destructor = destructor;
o->data = user_data;
return o;
}
/*
* Acquire a reference object. The caller must hold a reference
* to the object, or know for certain that a reference is held
* and will continue to be held while this call is in progress.
*/
void
object_acquire(Object *o)
{
PR_ASSERT(NULL != o);
PR_AtomicIncrement(&o->refcnt);
}
/*
* Release a reference to an object. The pointer to the object
* should not be referenced after this call is made, since the
* object may be destroyed if this is the last reference to it.
*/
void
object_release(Object *o)
{
PRInt32 refcnt_after_release;
PR_ASSERT(NULL != o);
refcnt_after_release = PR_AtomicDecrement(&o->refcnt);
PR_ASSERT(refcnt_after_release >= 0);
if (refcnt_after_release == 0)
{
/* Object can be destroyed */
if (o->destructor)
o->destructor(&o->data);
/* Make it harder to reuse a dangling pointer */
o->data = NULL;
o->destructor = NULL;
o->refcnt = -9999;
slapi_ch_free((void **)&o);
}
}
/*
* Get the data pointer from an object.
* Results are undefined if the caller does not hold a reference
* to the object.
*/
void *
object_get_data(Object *o)
{
PR_ASSERT(NULL != o);
return o->data;
}
|
