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
|
// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_FUNCTIONAL_CONCURRENT_CLOSURES_H_
#define BASE_FUNCTIONAL_CONCURRENT_CLOSURES_H_
#include "base/base_export.h"
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/memory/raw_ptr.h"
#include "base/sequence_checker.h"
#include "base/task/bind_post_task.h"
namespace base {
// OVERVIEW:
//
// ConcurrentClosures is a OnceClosure version of ConcurrentCallbacks<T> and an
// alternative to BarrierClosure, it dispenses OnceClosures via CreateClosure()
// and invokes the closure passed to Done() after all prior closures have been
// run.
//
// ConcurrentClosures is intended to be used over BarrierClosure in
// cases where the count is unknown prior to requiring a closure to start a
// task, and for cases where the count is manually derived from the code and
// subject to human error.
//
// IMPORTANT NOTES:
//
// - ConcurrentClosures is NOT thread safe.
// - The done closure will NOT be run synchronously, it will be PostTask() to
// the sequence that Done() was invoked on.
// - ConcurrentClosures cannot be used after Done() is called, a CHECK verifies
// this.
//
// TYPICAL USAGE:
//
// void DoABC(OnceClosure closure) {
// base::ConcurrentClosures concurrent;
//
// DoA(concurrent.CreateClosure());
// DoB(concurrent.CreateClosure());
// DoC(concurrent.CreateClosure());
//
// std::move(concurrent).Done(closure);
// }
class BASE_EXPORT ConcurrentClosures {
public:
ConcurrentClosures();
~ConcurrentClosures();
// Create a closure for the done closure to wait for.
[[nodiscard]] OnceClosure CreateClosure();
// Finish creating concurrent closures and provide done closure to run once
// all prior closures have executed.
// `this` is no longer usable after calling Done(), must be called with
// std::move().
void Done(OnceClosure done_closure, const Location& location = FROM_HERE) &&;
private:
class Info {
public:
Info();
~Info();
void Run();
size_t pending_ GUARDED_BY_CONTEXT(sequence_checker_) = 0u;
OnceClosure done_closure_ GUARDED_BY_CONTEXT(sequence_checker_);
SEQUENCE_CHECKER(sequence_checker_);
};
RepeatingClosure info_run_closure_;
// info_ is owned by info_run_closure_.
raw_ptr<Info> info_;
};
} // namespace base
#endif // BASE_FUNCTIONAL_CONCURRENT_CLOSURES_H_
|
