include/babeltrace/object-internal.h

   1 #ifndef BABELTRACE_OBJECT_INTERNAL_H
   2 #define BABELTRACE_OBJECT_INTERNAL_H
   3
   4 /*
   5  * Babeltrace - Base object
   6  *
   7  * Copyright 2015 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   8  *
   9  * Author: Jérémie Galarneau <jeremie.galarneau@efficios.com>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  27  * SOFTWARE.
  28  */
  29
  30 #include <babeltrace/ref-internal.h>
  31 #include <babeltrace/ref.h>
  32 #include <babeltrace/assert-internal.h>
  33
  34 /**
  35  * All objects publicly exposed by Babeltrace APIs must contain this structure
  36  * as their first member. This allows the unification of all ref counting
  37  * mechanisms and may be used to provide more base functionality to all
  38  * objects.
  39  */
  40 struct bt_object {
  41         struct bt_ref ref_count;
  42         /* Class-specific, optional release function. */
  43         bt_object_release_func release;
  44         /* Class-specific, optional "parent is owner" notification listener. */
  45         bt_object_release_func parent_is_owner_listener;
  46         /* @see doc/ref-counting.md */
  47         struct bt_object *parent;
  48 };
  49
  50 static inline
  51 long bt_object_get_ref_count(const void *ptr)
  52 {
  53         const struct bt_object *obj = ptr;
  54
  55         return obj->ref_count.count;
  56 }
  57
  58 static inline
  59 void bt_object_release(void *ptr)
  60 {
  61         struct bt_object *obj = ptr;
  62
  63 #ifdef BT_LOGV
  64         BT_LOGV("Releasing object: addr=%p, ref-count=%lu", ptr,
  65                 obj->ref_count.count);
  66 #endif
  67
  68         if (obj && obj->release && bt_object_get_ref_count(obj) == 0) {
  69                 obj->release(obj);
  70         }
  71 }
  72
  73 static inline
  74 void generic_release(struct bt_object *obj)
  75 {
  76         if (obj->parent) {
  77                 struct bt_object *parent = obj->parent;
  78
  79 #ifdef BT_LOGV
  80                 BT_LOGV("Releasing parented object: addr=%p, ref-count=%lu, "
  81                         "parent-addr=%p, parent-ref-count=%lu",
  82                         obj, obj->ref_count.count,
  83                         parent, parent->ref_count.count);
  84 #endif
  85
  86                 if (obj->parent_is_owner_listener) {
  87                         /*
  88                          * Object has a chance to destroy itself here
  89                          * under certain conditions and notify its
  90                          * parent. At this point the parent is
  91                          * guaranteed to exist because it's not put yet.
  92                          */
  93                         obj->parent_is_owner_listener(obj);
  94                 }
  95
  96                 /* The release function will be invoked by the parent. */
  97                 bt_put(parent);
  98         } else {
  99                 bt_object_release(obj);
 100         }
 101 }
 102
 103 static inline
 104 struct bt_object *bt_object_borrow_parent(void *ptr)
 105 {
 106         struct bt_object *obj = ptr;
 107
 108         return obj ? obj->parent : NULL;
 109 }
 110
 111 static inline
 112 struct bt_object *bt_object_get_parent(void *ptr)
 113 {
 114         return bt_get(bt_object_borrow_parent(ptr));
 115 }
 116
 117 static inline
 118 void bt_object_set_parent(void *child_ptr, void *parent)
 119 {
 120         struct bt_object *child = child_ptr;
 121
 122         if (!child) {
 123                 return;
 124         }
 125
 126 #ifdef BT_LOGV
 127         BT_LOGV("Setting object's parent: addr=%p, parent-addr=%p",
 128                 child_ptr, parent);
 129 #endif
 130
 131         /*
 132          * It is assumed that a "child" being "parented" is publicly reachable.
 133          * Therefore, a reference to its parent must be taken. The reference
 134          * to the parent will be released once the object's reference count
 135          * falls to zero.
 136          */
 137         BT_PUT(child->parent);
 138         child->parent = bt_get(parent);
 139 }
 140
 141 static inline
 142 void bt_object_init(void *ptr, bt_object_release_func release)
 143 {
 144         struct bt_object *obj = ptr;
 145
 146         obj->release = release;
 147         obj->parent = NULL;
 148         bt_ref_init(&obj->ref_count, generic_release);
 149 }
 150
 151 static inline
 152 void bt_object_set_parent_is_owner_listener(void *obj,
 153                 bt_object_release_func cb)
 154 {
 155         BT_ASSERT(obj);
 156         ((struct bt_object *) obj)->parent_is_owner_listener = cb;
 157 }
 158
 159 #endif /* BABELTRACE_OBJECT_INTERNAL_H */