1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_CRITICAL_CLOSURE_H_
6#define BASE_CRITICAL_CLOSURE_H_
7
8#include "base/callback.h"
9
10#if defined(OS_IOS)
11#include "base/bind.h"
12#include "base/ios/scoped_critical_action.h"
13#endif
14
15namespace base {
16
17namespace internal {
18
19#if defined(OS_IOS)
20// Returns true if multi-tasking is supported on this iOS device.
21bool IsMultiTaskingSupported();
22
23// This class wraps a closure so it can continue to run for a period of time
24// when the application goes to the background by using
25// |ios::ScopedCriticalAction|.
26template <typename R>
27class CriticalClosure {
28 public:
29  explicit CriticalClosure(const Callback<R(void)>& closure)
30      : closure_(closure) {}
31
32  ~CriticalClosure() {}
33
34  R Run() {
35    return closure_.Run();
36  }
37
38 private:
39  ios::ScopedCriticalAction critical_action_;
40  Callback<R(void)> closure_;
41
42  DISALLOW_COPY_AND_ASSIGN(CriticalClosure);
43};
44#endif  // defined(OS_IOS)
45
46}  // namespace internal
47
48// Returns a closure (which may return a result, but must not require any extra
49// arguments) that will continue to run for a period of time when the
50// application goes to the background if possible on platforms where
51// applications don't execute while backgrounded, otherwise the original task is
52// returned.
53//
54// Example:
55//   file_message_loop_proxy_->PostTask(
56//       FROM_HERE,
57//       MakeCriticalClosure(base::Bind(&WriteToDiskTask, path_, data)));
58//
59// Note new closures might be posted in this closure. If the new closures need
60// background running time, |MakeCriticalClosure| should be applied on them
61// before posting.
62#if defined(OS_IOS)
63template <typename R>
64Callback<R(void)> MakeCriticalClosure(const Callback<R(void)>& closure) {
65  DCHECK(internal::IsMultiTaskingSupported());
66  return base::Bind(&internal::CriticalClosure<R>::Run,
67                    Owned(new internal::CriticalClosure<R>(closure)));
68}
69#else  // defined(OS_IOS)
70template <typename R>
71inline Callback<R(void)> MakeCriticalClosure(const Callback<R(void)>& closure) {
72  // No-op for platforms where the application does not need to acquire
73  // background time for closures to finish when it goes into the background.
74  return closure;
75}
76#endif  // defined(OS_IOS)
77
78}  // namespace base
79
80#endif  // BASE_CRITICAL_CLOSURE_H_
81