Panda3D

globalPointerRegistry.h
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1 /**
2 * PANDA 3D SOFTWARE
3 * Copyright (c) Carnegie Mellon University. All rights reserved.
4 *
5 * All use of this software is subject to the terms of the revised BSD
6 * license. You should have received a copy of this license along
7 * with this source code in a file named "LICENSE."
8 *
9 * @file globalPointerRegistry.h
10 * @author drose
11 * @date 2000-02-03
12 */
13
14 #ifndef GLOBALPOINTERREGISTRY_H
15 #define GLOBALPOINTERREGISTRY_H
16
17 #include "pandabase.h"
18
19 #include "typedObject.h"
20
21 #include "pmap.h"
22
23 /**
24 * This class maintains a one-to-one mapping from TypeHandle to a void *
25 * pointer. Its purpose is to store a pointer to some class data for a given
26 * class.
27 *
28 * Normally, one would simply use a static data member to store class data.
29 * However, when the static data is associated with a template class, the
30 * dynamic loader may have difficulty in properly resolving the statics.
31 *
32 * Consider: class foo<int> defines a static member, _a. There should be only
33 * one instance of _a shared between all instances of foo<int>, and there will
34 * be a different instance of _a shared between all instances of foo<float>.
35 *
36 * Now suppose that two different shared libraries instantiate foo<int>. In
37 * each .so, there exists a different foo<int>::_a. It is the loader's job to
38 * recognize this and collapse them together when both libraries are loaded.
39 * This usually works, but sometimes it doesn't, and you end up with two
40 * different instances of foo<int>::_a; some functions see one instance, while
41 * others see the other. We have particularly seen this problem occur under
42 * Linux with gcc.
43 *
44 * This class attempts to circumvent the problem by managing pointers to data
45 * based on TypeHandle. Since the TypeHandle will already be unique based on
46 * the string name supplied to the init_type() function, it can be used to
47 * differentiate foo<int> from foo<float>, while allowing different instances
48 * of foo<int> to guarantee that they share the same static data.
49 */
50 class EXPCL_PANDA_PUTIL GlobalPointerRegistry {
51 public:
52 INLINE static void *get_pointer(TypeHandle type);
53 INLINE static void store_pointer(TypeHandle type, void *ptr);
54 INLINE static void clear_pointer(TypeHandle type);
55
56 private:
57 // Nonstatic implementations of the above functions.
58 void *ns_get_pointer(TypeHandle type) const;
59 void ns_store_pointer(TypeHandle type, void *ptr);
60 void ns_clear_pointer(TypeHandle type);
61
62 INLINE static GlobalPointerRegistry *get_global_ptr();
63 static GlobalPointerRegistry *_global_ptr;
64
65 private:
66 typedef phash_map<TypeHandle, void *> Pointers;
67 Pointers _pointers;
68 };
69
70 #include "globalPointerRegistry.I"
71
72 #endif
GlobalPointerRegistry
This class maintains a one-to-one mapping from TypeHandle to a void * pointer.
Definition: globalPointerRegistry.h:50
TypeHandle
TypeHandle is the identifier used to differentiate C++ class types.
Definition: typeHandle.h:81
globalPointerRegistry.I
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
pandabase.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
pmap.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
typedObject.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.