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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
/**
* @file llhandle.h
* @brief "Handle" to an object (usually a floater) whose lifetime you don't
* control.
*
* $LicenseInfo:firstyear=2001&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#ifndef LLHANDLE_H
#define LLHANDLE_H
#include "llpointer.h"
#include <boost/type_traits/is_convertible.hpp>
#include <boost/utility/enable_if.hpp>
class LLTombStone : public LLRefCount
{
public:
LLTombStone(void* target = NULL) : mTarget(target) {}
void setTarget(void* target) { mTarget = target; }
void* getTarget() const { return mTarget; }
private:
mutable void* mTarget;
};
// LLHandles are used to refer to objects whose lifetime you do not control or influence.
// Calling get() on a handle will return a pointer to the referenced object or NULL,
// if the object no longer exists. Note that during the lifetime of the returned pointer,
// you are assuming that the object will not be deleted by any action you perform,
// or any other thread, as normal when using pointers, so avoid using that pointer outside of
// the local code block.
//
// https://wiki.lindenlab.com/mediawiki/index.php?title=LLHandle&oldid=79669
template <typename T>
class LLHandle
{
template <typename U> friend class LLHandle;
template <typename U> friend class LLHandleProvider;
public:
LLHandle() : mTombStone(getDefaultTombStone()) {}
template<typename U>
LLHandle(const LLHandle<U>& other, typename boost::enable_if< typename boost::is_convertible<U*, T*> >::type* dummy = 0)
: mTombStone(other.mTombStone)
{}
bool isDead() const
{
return mTombStone->getTarget() == NULL;
}
void markDead()
{
mTombStone = getDefaultTombStone();
}
T* get() const
{
return reinterpret_cast<T*>(mTombStone->getTarget());
}
friend bool operator== (const LLHandle<T>& lhs, const LLHandle<T>& rhs)
{
return lhs.mTombStone == rhs.mTombStone;
}
friend bool operator!= (const LLHandle<T>& lhs, const LLHandle<T>& rhs)
{
return !(lhs == rhs);
}
friend bool operator< (const LLHandle<T>& lhs, const LLHandle<T>& rhs)
{
return lhs.mTombStone < rhs.mTombStone;
}
friend bool operator> (const LLHandle<T>& lhs, const LLHandle<T>& rhs)
{
return lhs.mTombStone > rhs.mTombStone;
}
protected:
LLPointer<LLTombStone> mTombStone;
private:
typedef T* pointer_t;
static LLPointer<LLTombStone>& getDefaultTombStone()
{
static LLPointer<LLTombStone> sDefaultTombStone = new LLTombStone;
return sDefaultTombStone;
}
};
template <typename T>
class LLRootHandle : public LLHandle<T>
{
public:
typedef LLRootHandle<T> self_t;
typedef LLHandle<T> base_t;
LLRootHandle(T* object) { bind(object); }
LLRootHandle() {};
~LLRootHandle() { unbind(); }
// this is redundant, since an LLRootHandle *is* an LLHandle
//LLHandle<T> getHandle() { return LLHandle<T>(*this); }
void bind(T* object)
{
// unbind existing tombstone
if (LLHandle<T>::mTombStone.notNull())
{
if (LLHandle<T>::mTombStone->getTarget() == (void*)object) return;
LLHandle<T>::mTombStone->setTarget(NULL);
}
// tombstone reference counted, so no paired delete
LLHandle<T>::mTombStone = new LLTombStone((void*)object);
}
void unbind()
{
LLHandle<T>::mTombStone->setTarget(NULL);
}
//don't allow copying of root handles, since there should only be one
private:
LLRootHandle(const LLRootHandle& other) {};
};
// Use this as a mixin for simple classes that need handles and when you don't
// want handles at multiple points of the inheritance hierarchy
template <typename T>
class LLHandleProvider
{
public:
LLHandle<T> getHandle() const
{
// perform lazy binding to avoid small tombstone allocations for handle
// providers whose handles are never referenced
mHandle.bind(static_cast<T*>(const_cast<LLHandleProvider<T>* >(this)));
return mHandle;
}
protected:
typedef LLHandle<T> handle_type_t;
LLHandleProvider()
{
// provided here to enforce T deriving from LLHandleProvider<T>
}
template <typename U>
LLHandle<U> getDerivedHandle(typename boost::enable_if< typename boost::is_convertible<U*, T*> >::type* dummy = 0) const
{
LLHandle<U> downcast_handle;
downcast_handle.mTombStone = getHandle().mTombStone;
return downcast_handle;
}
private:
mutable LLRootHandle<T> mHandle;
};
#endif
|
