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
  33 /**
  34  * All objects publicly exposed by Babeltrace APIs must contain this structure
  35  * as their first member. This allows the unification of all ref counting
  36  * mechanisms and may be used to provide more base functionality to all
  37  * objects.
  38  */
  39 struct bt_object {
  40         struct bt_ref ref_count;
  41         /* Class-specific, optional release function. */
  42         bt_object_release_func release;
  43         /* Class-specific, optional "parent is owner" notification listener. */
  44         bt_object_release_func parent_is_owner_listener;
  45         /* @see doc/ref-counting.md */
  46         struct bt_object *parent;
  47 };
  48
  49 static inline
  50 long bt_object_get_ref_count(const void *ptr)
  51 {
  52         const struct bt_object *obj = ptr;
  53
  54         return obj->ref_count.count;
  55 }
  56
  57 static inline
  58 void bt_object_release(void *ptr)
  59 {
  60         struct bt_object *obj = ptr;
  61
  62         if (obj && obj->release && !bt_object_get_ref_count(obj)) {
  63                 obj->release(obj);
  64         }
  65 }
  66
  67 static inline
  68 void generic_release(struct bt_object *obj)
  69 {
  70         if (obj->parent) {
  71                 void *parent = obj->parent;
  72
  73                 if (obj->parent_is_owner_listener) {
  74                         /*
  75                          * Object has a chance to destroy itself here
  76                          * under certain conditions and notify its
  77                          * parent. At this point the parent is
  78                          * guaranteed to exist because it's not put yet.
  79                          */
  80                         obj->parent_is_owner_listener(obj);
  81                 }
  82
  83                 /* The release function will be invoked by the parent. */
  84                 bt_put(parent);
  85         } else {
  86                 bt_object_release(obj);
  87         }
  88 }
  89
  90 static inline
  91 struct bt_object *bt_object_borrow_parent(void *ptr)
  92 {
  93         struct bt_object *obj = ptr;
  94
  95         return obj ? obj->parent : NULL;
  96 }
  97
  98 static inline
  99 struct bt_object *bt_object_get_parent(void *ptr)
 100 {
 101         return bt_get(bt_object_borrow_parent(ptr));
 102 }
 103
 104 static inline
 105 void bt_object_set_parent(void *child_ptr, void *parent)
 106 {
 107         struct bt_object *child = child_ptr;
 108
 109         if (!child) {
 110                 return;
 111         }
 112
 113         /*
 114          * It is assumed that a "child" being "parented" is publicly reachable.
 115          * Therefore, a reference to its parent must be taken. The reference
 116          * to the parent will be released once the object's reference count
 117          * falls to zero.
 118          */
 119         BT_PUT(child->parent);
 120         child->parent = bt_get(parent);
 121 }
 122
 123 static inline
 124 void bt_object_init(void *ptr, bt_object_release_func release)
 125 {
 126         struct bt_object *obj = ptr;
 127
 128         obj->release = release;
 129         obj->parent = NULL;
 130         bt_ref_init(&obj->ref_count, generic_release);
 131 }
 132
 133 static inline
 134 void bt_object_set_parent_is_owner_listener(void *obj,
 135                 bt_object_release_func cb)
 136 {
 137         assert(obj);
 138         ((struct bt_object *) obj)->parent_is_owner_listener = cb;
 139 }
 140
 141 #endif /* BABELTRACE_OBJECT_INTERNAL_H */