text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef BASE_CRITICAL_CLOSURE_H_
  #define BASE_CRITICAL_CLOSURE_H_
  
  #include <utility>
  
  #include "base/callback.h"
  #include "base/location.h"
  #include "base/strings/string_piece.h"
  #include "build/build_config.h"
  
  #if defined(OS_IOS)
  #include "base/bind.h"
  #include "base/ios/scoped_critical_action.h"
  #endif
  
  namespace base {
  
  namespace internal {
  
  #if defined(OS_IOS)
  // Returns true if multi-tasking is supported on this iOS device.
  bool IsMultiTaskingSupported();
  
  // This class wraps a closure so it can continue to run for a period of time
  // when the application goes to the background by using
  // |ios::ScopedCriticalAction|.
  class CriticalClosure {
   public:
    explicit CriticalClosure(StringPiece task_name, OnceClosure closure);
    CriticalClosure(const CriticalClosure&) = delete;
    CriticalClosure& operator=(const CriticalClosure&) = delete;
    ~CriticalClosure();
    void Run();
  
   private:
    ios::ScopedCriticalAction critical_action_;
    OnceClosure closure_;
  };
  #endif  // defined(OS_IOS)
  
  }  // namespace internal
  
  // Returns a closure that will continue to run for a period of time when the
  // application goes to the background if possible on platforms where
  // applications don't execute while backgrounded, otherwise the original task is
  // returned.
  //
  // Example:
  //   file_task_runner_->PostTask(
  //       FROM_HERE,
  //       MakeCriticalClosure(task_name,
  //                           base::BindOnce(&WriteToDiskTask, path_, data)));
  //
  // Note new closures might be posted in this closure. If the new closures need
  // background running time, |MakeCriticalClosure| should be applied on them
  // before posting. |task_name| is used by the platform to identify any tasks
  // that do not complete in time for suspension.
  #if defined(OS_IOS)
  inline OnceClosure MakeCriticalClosure(StringPiece task_name,
                                         OnceClosure closure) {
    DCHECK(internal::IsMultiTaskingSupported());
    return base::BindOnce(
        &internal::CriticalClosure::Run,
        Owned(new internal::CriticalClosure(task_name, std::move(closure))));
  }
  
  inline OnceClosure MakeCriticalClosure(const Location& posted_from,
                                         OnceClosure closure) {
    return MakeCriticalClosure(posted_from.ToString(), std::move(closure));
  }
  
  #else  // defined(OS_IOS)
  inline OnceClosure MakeCriticalClosure(StringPiece task_name,
                                         OnceClosure closure) {
    // No-op for platforms where the application does not need to acquire
    // background time for closures to finish when it goes into the background.
    return closure;
  }
  
  inline OnceClosure MakeCriticalClosure(const Location& posted_from,
                                         OnceClosure closure) {
    return closure;
  }
  
  #endif  // defined(OS_IOS)
  
  }  // namespace base
  
  #endif  // BASE_CRITICAL_CLOSURE_H_
  