MuldeR's Utilities for Qt MUtilities

Lazy.h
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1 // MuldeR's Utilities for Qt
3 // Copyright (C) 2004-2018 LoRd_MuldeR <MuldeR2@GMX.de>
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 //
19 // http://www.gnu.org/licenses/lgpl-2.1.txt
21
27 #pragma once
28
29 //MUtils
30 #include <MUtils/Global.h>
31 #include <MUtils/Exception.h>
32
33 //Qt
34 #include <QAtomicPointer>
35
36 //CRT
37 #include <functional>
38
39 namespace MUtils
40 {
48 template<typename T> class Lazy
49 {
50 public:
51 Lazy(std::function<T*(void)> &&initializer) : m_initializer(initializer) { }
52
53 T& operator*(void)
54 {
55 while (!m_value)
56 {
57 if (T *const value = m_initializer())
58 {
59 if (!m_value.testAndSetOrdered(NULL, value))
60 {
61 delete value; /*too late*/
62 }
63 }
64 else
65 {
66 MUTILS_THROW("Initializer returned NULL!");
67 }
68 }
69 return *m_value;
70 }
71
72 private:
73 QAtomicPointer<T> m_value;
74 const std::function<T*(void)> m_initializer;
75 };
76 }
Global.h
This file contains miscellaneous functions that are generally useful for Qt-based applications...
MUtils::Lazy
Lazy initialization template class.
Definition: Lazy.h:48
MUtils
Global MUtils namespace.
Definition: CPUFeatures.h:37