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
|
/**
* @file lllazyvalue.h
* @brief generic functor/value abstraction for lazy evaluation of a value
* parsing construction parameters from xml and LLSD
*
* $LicenseInfo:firstyear=2008&license=viewerlgpl$
* 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 LL_LAZY_VALUE_H
#define LL_LAZY_VALUE_H
#include <boost/function.hpp>
// Holds on to a value of type T *or* calls a functor to generate a value of type T
template<typename T>
class LLLazyValue
{
public:
typedef typename boost::add_reference<typename boost::add_const<T>::type>::type T_const_ref;
typedef typename boost::function<T_const_ref (void)> function_type;
public:
LLLazyValue(const function_type& value)
: mValueGetter(value)
{}
LLLazyValue(T_const_ref value)
: mValue(value)
{}
LLLazyValue()
: mValue()
{}
void set(const LLLazyValue& val)
{
mValueGetter = val.mValueGetter;
}
void set(T_const_ref val)
{
mValue = val;
mValueGetter = NULL;
}
T_const_ref get() const
{
if (!mValueGetter.empty())
{
return mValueGetter();
}
return mValue;
}
bool isUsingFunction() const
{
return mValueGetter != NULL;
}
private:
function_type mValueGetter;
T mValue;
};
#endif // LL_LAZY_VALUE_H
|
