Panda3D
copyOnWriteObject.h
Go to the documentation of this file.
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 copyOnWriteObject.h
10  * @author drose
11  * @date 2007-04-09
12  */
13 
14 #ifndef COPYONWRITEOBJECT_H
15 #define COPYONWRITEOBJECT_H
16 
17 #include "pandabase.h"
18 
20 #include "pmutex.h"
21 #include "conditionVar.h"
22 #include "mutexHolder.h"
23 
24 // Should we implement full thread protection for CopyOnWritePointer? If we
25 // can be assured that no other thread will interrupt while a write pointer is
26 // held, we don't need thread protection.
27 
28 // Nowadays, this is the same thing as asking if HAVE_THREADS is defined.
29 // Maybe we'll just replace COW_THREADED with HAVE_THREADS in the future.
30 #ifdef HAVE_THREADS
31  #define COW_THREADED 1
32 #else
33  #undef COW_THREADED
34 #endif
35 
36 /**
37  * This base class provides basic reference counting, but also can be used
38  * with a CopyOnWritePointer to provide get_read_pointer() and
39  * get_write_pointer().
40  */
41 class EXPCL_PANDA_PUTIL CopyOnWriteObject : public CachedTypedWritableReferenceCount {
42 public:
43  INLINE CopyOnWriteObject();
44  INLINE CopyOnWriteObject(const CopyOnWriteObject &copy);
45  INLINE void operator = (const CopyOnWriteObject &copy);
46 
47 PUBLISHED:
48 #ifdef COW_THREADED
49  virtual bool unref() const;
50  INLINE void cache_ref() const;
51  INLINE bool cache_unref() const;
52 
53 public:
54  void cache_ref_only() const;
55 #endif // COW_THREADED
56 
57 protected:
58  virtual PT(CopyOnWriteObject) make_cow_copy()=0;
59 
60 private:
61 #ifdef COW_THREADED
62  enum LockStatus {
63  LS_unlocked,
64  LS_locked_read,
65  LS_locked_write,
66  };
67  Mutex _lock_mutex;
68  ConditionVar _lock_cvar;
69  LockStatus _lock_status;
70  Thread *_locking_thread;
71 #endif // COW_THREADED
72 
73 public:
74  virtual TypeHandle get_type() const {
75  return get_class_type();
76  }
77  virtual TypeHandle force_init_type() {init_type(); return get_class_type();}
78 
79 PUBLISHED:
80  static TypeHandle get_class_type() {
81  return _type_handle;
82  }
83 
84 public:
85  static void init_type() {
86  CachedTypedWritableReferenceCount::init_type();
87  register_type(_type_handle, "CopyOnWriteObject",
88  CachedTypedWritableReferenceCount::get_class_type());
89  }
90 
91 private:
92  static TypeHandle _type_handle;
93 
94  friend class CopyOnWritePointer;
95 };
96 
97 /**
98  * This is similar to RefCountObj, but it implements a CopyOnWriteObject
99  * inheritance instead of a ReferenceCount inheritance.
100  */
101 template<class Base>
102 class CopyOnWriteObj : public CopyOnWriteObject, public Base {
103 public:
104  INLINE CopyOnWriteObj();
105  INLINE CopyOnWriteObj(const Base &copy);
106  INLINE CopyOnWriteObj(const CopyOnWriteObj<Base> &copy);
107  ALLOC_DELETED_CHAIN(CopyOnWriteObj<Base>);
108 
109 protected:
110  virtual PT(CopyOnWriteObject) make_cow_copy();
111 
112 public:
113  virtual TypeHandle get_type() const {
114  return get_class_type();
115  }
116  virtual TypeHandle force_init_type() {init_type(); return get_class_type();}
117 
118 PUBLISHED:
119  static TypeHandle get_class_type() {
120  return _type_handle;
121  }
122 
123 public:
124  static void init_type();
125 
126 private:
127  static TypeHandle _type_handle;
128 };
129 
130 /**
131  * For objects (e.g. pvectors) whose constructor takes a single parameter.
132  */
133 template<class Base, class Param1>
134 class CopyOnWriteObj1 : public CopyOnWriteObject, public Base {
135 public:
136  INLINE CopyOnWriteObj1(Param1 p1);
137  INLINE CopyOnWriteObj1(const Base &copy);
139 
141  ALLOC_DELETED_CHAIN(ThisClass)
142 
143 protected:
144  virtual PT(CopyOnWriteObject) make_cow_copy();
145 
146 public:
147  virtual TypeHandle get_type() const {
148  return get_class_type();
149  }
150  virtual TypeHandle force_init_type() {init_type(); return get_class_type();}
151 
152 PUBLISHED:
153  static TypeHandle get_class_type() {
154  return _type_handle;
155  }
156 
157 public:
158  static void init_type();
159 
160 private:
161  static TypeHandle _type_handle;
162 };
163 
164 // We can safely redefine this as a no-op.
165 template<>
166 INLINE void PointerToBase<CopyOnWriteObject>::update_type(To *ptr) {}
167 
168 #include "copyOnWriteObject.I"
169 
170 #endif
CachedTypedWritableReferenceCount
This is a special extension to ReferenceCount that includes dual reference counts: the standard refer...
Definition: cachedTypedWritableReferenceCount.h:34
CopyOnWritePointer
This safely stores the primary, owned pointer to a CopyOnWriteObject.
Definition: copyOnWritePointer.h:31
pandabase.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
register_type
void register_type(TypeHandle &type_handle, const std::string &name)
This inline function is just a convenient way to call TypeRegistry::register_type(),...
Definition: register_type.I:22
CopyOnWriteObj1
For objects (e.g.
Definition: copyOnWriteObject.h:134
TypeHandle
TypeHandle is the identifier used to differentiate C++ class types.
Definition: typeHandle.h:81
CopyOnWriteObj
This is similar to RefCountObj, but it implements a CopyOnWriteObject inheritance instead of a Refere...
Definition: copyOnWriteObject.h:102
PointerToBase
This is the base class for PointerTo and ConstPointerTo.
Definition: pointerToBase.h:29
copyOnWriteObject.I
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
CopyOnWriteObject
This base class provides basic reference counting, but also can be used with a CopyOnWritePointer to ...
Definition: copyOnWriteObject.h:41
CachedTypedWritableReferenceCount::cache_ref
void cache_ref() const
Explicitly increments the cache reference count and the normal reference count simultaneously.
Definition: cachedTypedWritableReferenceCount.I:119
Mutex
A standard mutex, or mutual exclusion lock.
Definition: pmutex.h:40
cachedTypedWritableReferenceCount.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
pmutex.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
conditionVar.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
CachedTypedWritableReferenceCount::cache_unref
bool cache_unref() const
Explicitly decrements the cache reference count and the normal reference count simultaneously.
Definition: cachedTypedWritableReferenceCount.I:136
ConditionVar
A condition variable, usually used to communicate information about changing state to a thread that i...
Definition: conditionVar.h:43
mutexHolder.h
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
ReferenceCount::unref
virtual bool unref() const
Explicitly decrements the reference count.
Definition: referenceCount.I:179
CachedTypedWritableReferenceCount::cache_ref_only
void cache_ref_only() const
Decrements the cache reference count without affecting the normal reference count.
Definition: cachedTypedWritableReferenceCount.I:168
Thread
A thread; that is, a lightweight process.
Definition: thread.h:46