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1 /* | |
2 * Copyright (C) 2011 Google Inc. All rights reserved. | |
3 * | |
4 * Redistribution and use in source and binary forms, with or without | |
5 * modification, are permitted provided that the following conditions | |
6 * are met: | |
7 * | |
8 * 1. Redistributions of source code must retain the above copyright | |
9 * notice, this list of conditions and the following disclaimer. | |
10 * 2. Redistributions in binary form must reproduce the above copyright | |
11 * notice, this list of conditions and the following disclaimer in the | |
12 * documentation and/or other materials provided with the distribution. | |
13 * | |
14 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY | |
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED | |
16 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | |
17 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY | |
18 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | |
19 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
20 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND | |
21 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
24 */ | |
25 | |
26 #ifndef TemporaryChange_h | |
27 #define TemporaryChange_h | |
28 | |
29 #include <wtf/Noncopyable.h> | |
30 | |
31 namespace WTF { | |
32 | |
33 // TemporaryChange<> is useful for setting a variable to a new value only within
a | |
34 // particular scope. An TemporaryChange<> object changes a variable to its origi
nal | |
35 // value upon destruction, making it an alternative to writing "var = false;" | |
36 // or "var = oldVal;" at all of a block's exit points. | |
37 // | |
38 // This should be obvious, but note that an TemporaryChange<> instance should ha
ve a | |
39 // shorter lifetime than its scopedVariable, to prevent invalid memory writes | |
40 // when the TemporaryChange<> object is destroyed. | |
41 | |
42 template<typename T> | |
43 class TemporaryChange { | |
44 WTF_MAKE_NONCOPYABLE(TemporaryChange); | |
45 public: | |
46 TemporaryChange(T& scopedVariable, T newValue) | |
47 : m_scopedVariable(scopedVariable) | |
48 , m_originalValue(scopedVariable) | |
49 { | |
50 m_scopedVariable = newValue; | |
51 } | |
52 | |
53 ~TemporaryChange() | |
54 { | |
55 m_scopedVariable = m_originalValue; | |
56 } | |
57 | |
58 | |
59 private: | |
60 T& m_scopedVariable; | |
61 T m_originalValue; | |
62 }; | |
63 | |
64 } | |
65 | |
66 using WTF::TemporaryChange; | |
67 | |
68 #endif | |
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