Home | History | Annotate | Download | only in base 
      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 #include "base/macros.h"
     10 #include "build/build_config.h"
     11 
     12 #if defined(OS_IOS)
     13 #include "base/bind.h"
     14 #include "base/ios/scoped_critical_action.h"
     15 #endif
     16 
     17 namespace base {
     18 
     19 namespace internal {
     20 
     21 #if defined(OS_IOS)
     22 // Returns true if multi-tasking is supported on this iOS device.
     23 bool IsMultiTaskingSupported();
     24 
     25 // This class wraps a closure so it can continue to run for a period of time
     26 // when the application goes to the background by using
     27 // |ios::ScopedCriticalAction|.
     28 template <typename R>
     29 class CriticalClosure {
     30  public:
     31   explicit CriticalClosure(const Callback<R(void)>& closure)
     32       : closure_(closure) {}
     33 
     34   ~CriticalClosure() {}
     35 
     36   R Run() {
     37     return closure_.Run();
     38   }
     39 
     40  private:
     41   ios::ScopedCriticalAction critical_action_;
     42   Callback<R(void)> closure_;
     43 
     44   DISALLOW_COPY_AND_ASSIGN(CriticalClosure);
     45 };
     46 #endif  // defined(OS_IOS)
     47 
     48 }  // namespace internal
     49 
     50 // Returns a closure (which may return a result, but must not require any extra
     51 // arguments) that will continue to run for a period of time when the
     52 // application goes to the background if possible on platforms where
     53 // applications don't execute while backgrounded, otherwise the original task is
     54 // returned.
     55 //
     56 // Example:
     57 //   file_task_runner_->PostTask(
     58 //       FROM_HERE,
     59 //       MakeCriticalClosure(base::Bind(&WriteToDiskTask, path_, data)));
     60 //
     61 // Note new closures might be posted in this closure. If the new closures need
     62 // background running time, |MakeCriticalClosure| should be applied on them
     63 // before posting.
     64 #if defined(OS_IOS)
     65 template <typename R>
     66 Callback<R(void)> MakeCriticalClosure(const Callback<R(void)>& closure) {
     67   DCHECK(internal::IsMultiTaskingSupported());
     68   return base::Bind(&internal::CriticalClosure<R>::Run,
     69                     Owned(new internal::CriticalClosure<R>(closure)));
     70 }
     71 #else  // defined(OS_IOS)
     72 template <typename R>
     73 inline Callback<R(void)> MakeCriticalClosure(const Callback<R(void)>& closure) {
     74   // No-op for platforms where the application does not need to acquire
     75   // background time for closures to finish when it goes into the background.
     76   return closure;
     77 }
     78 #endif  // defined(OS_IOS)
     79 
     80 }  // namespace base
     81 
     82 #endif  // BASE_CRITICAL_CLOSURE_H_
     83