base/critical_closure.h

   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
  15 namespace base {
  16
  17 namespace internal {
  18
  19 #if defined(OS_IOS)
  20 // Returns true if multi-tasking is supported on this iOS device.
  21 bool 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|.
  26 template <typename R>
  27 class 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_task_runner_->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)
  63 template <typename R>
  64 Callback<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)
  70 template <typename R>
  71 inline 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_