Rietveld Code Review Tool
Help | Bug tracker | Discussion group | Source code

Side by Side Diff: src/plugin/Placeholder.h

Issue 29323611: Issue #1234, #2058 - Rewrite log facility, improving thread implementation
Patch Set: address comments Created Feb. 4, 2016, 8:59 p.m.
Left:
Right:
Use n/p to move between diff chunks; N/P to move between comments.
Jump to:
View unified diff | Download patch
« no previous file with comments | « src/plugin/Config.h ('k') | src/plugin/PluginClass.h » ('j') | no next file with comments »
Toggle Intra-line Diffs ('i') | Expand Comments ('e') | Collapse Comments ('c') | Show Comments Hide Comments ('s')
OLDNEW
(Empty)
1 /*
2 * This file is part of Adblock Plus <https://adblockplus.org/>,
3 * Copyright (C) 2006-2015 Eyeo GmbH
4 *
5 * Adblock Plus is free software: you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 3 as
7 * published by the Free Software Foundation.
8 *
9 * Adblock Plus is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with Adblock Plus. If not, see <http://www.gnu.org/licenses/>.
16 */
17
18 /**
19 * Allows construction of an object in one block and usage in another.
20 *
21 * Splitting construction and usage is not necessary in all cases,
22 * but there are many when it is.
23 * In any relevant case it's necessary to define something in a context that con tains both blocks.
24 * One is when the class is not default-constructible.
25 * You might be able to construct an initial value if you know the class,
26 * but that's not the case in general for templates.
27 * Another is when there's no copy assignment available,
28 * such as std::unique_ptr.
29 *
30 * A 'Placeholder' can be initialized with either a copy or move constructor.
31 * We can't use assignment to initialize, because (in general) assignment assume s
32 * that the lvalue target is already initialized.
33 */
34 template<class T>
35 class Placeholder
36 {
37 /**
38 * We 'allocate' memory for the object in the instance itself;
39 * there's no use of the heap.
40 *
41 * Note that it's a normative standard that sizeof(char)==1
42 */
43 char storage[sizeof(T)];
44
45 public:
46 /**
47 * Initialize by copying a glvalue into our private storage.
48 */
49 void Construct(const T& x)
50 {
51 /*
52 * We use placement-new syntax to use our private storage.
53 * The constructor expression invokes the copy constructor.
54 */
55 new (&storage[0]) T(x);
56 }
57
58 /**
59 * Initialize by moving an rvalue into our private storage.
60 */
61 void Construct(T&& x)
62 {
63 /*
64 * We use placement-new syntax to use our private storage.
65 * We explicitly cast to an rvalue to ensure use of the move constructor.
66 */
67 new (&storage[0]) T(std::move(x));
68 }
69
70 /**
71 * Access the object in storage.
72 */
73 T& Object()
74 {
75 return *reinterpret_cast<T *>(&storage[0]);
76 }
77 };
78
OLDNEW
« no previous file with comments | « src/plugin/Config.h ('k') | src/plugin/PluginClass.h » ('j') | no next file with comments »

Powered by Google App Engine
This is Rietveld