base/critical_closure.h

   1 // Copyright 2012 The Chromium Authors
   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 <utility>
   9
  10 #include "base/functional/callback.h"
  11 #include "base/location.h"
  12 #include "base/strings/string_piece.h"
  13 #include "build/build_config.h"
  14
  15 #if BUILDFLAG(IS_IOS)
  16 #include "base/functional/bind.h"
  17 #include "base/ios/scoped_critical_action.h"
  18 #include "third_party/abseil-cpp/absl/types/optional.h"
  19 #endif
  20
  21 namespace base {
  22
  23 namespace internal {
  24
  25 #if BUILDFLAG(IS_IOS)
  26 // This class wraps a closure so it can continue to run for a period of time
  27 // when the application goes to the background by using
  28 // |ios::ScopedCriticalAction|.
  29 class ImmediateCriticalClosure {
  30  public:
  31   explicit ImmediateCriticalClosure(StringPiece task_name, OnceClosure closure);
  32   ImmediateCriticalClosure(const ImmediateCriticalClosure&) = delete;
  33   ImmediateCriticalClosure& operator=(const ImmediateCriticalClosure&) = delete;
  34   ~ImmediateCriticalClosure();
  35   void Run();
  36
  37  private:
  38   ios::ScopedCriticalAction critical_action_;
  39   OnceClosure closure_;
  40 };
  41
  42 // This class is identical to ImmediateCriticalClosure, but the critical action
  43 // is started when the action runs, not when the CriticalAction is created.
  44 class PendingCriticalClosure {
  45  public:
  46   explicit PendingCriticalClosure(StringPiece task_name, OnceClosure closure);
  47   PendingCriticalClosure(const PendingCriticalClosure&) = delete;
  48   PendingCriticalClosure& operator=(const PendingCriticalClosure&) = delete;
  49   ~PendingCriticalClosure();
  50   void Run();
  51
  52  private:
  53   absl::optional<ios::ScopedCriticalAction> critical_action_;
  54   std::string task_name_;
  55   OnceClosure closure_;
  56 };
  57 #endif  // BUILDFLAG(IS_IOS)
  58
  59 }  // namespace internal
  60
  61 // Returns a closure that will continue to run for a period of time when the
  62 // application goes to the background if possible on platforms where
  63 // applications don't execute while backgrounded, otherwise the original task is
  64 // returned. If |is_immediate| is true, the closure will immediately prevent
  65 // background suspension. Otherwise, the closure will wait to request background
  66 // permission until it is run.
  67 //
  68 // Example:
  69 //   file_task_runner_->PostTask(
  70 //       FROM_HERE,
  71 //       MakeCriticalClosure(task_name,
  72 //                           base::BindOnce(&WriteToDiskTask, path_, data)));
  73 //
  74 // Note new closures might be posted in this closure. If the new closures need
  75 // background running time, |MakeCriticalClosure| should be applied on them
  76 // before posting. |task_name| is used by the platform to identify any tasks
  77 // that do not complete in time for suspension.
  78 //
  79 // This function is used automatically for tasks posted to a sequence runner
  80 // using TaskShutdownBehavior::BLOCK_SHUTDOWN.
  81 #if BUILDFLAG(IS_IOS)
  82 inline OnceClosure MakeCriticalClosure(StringPiece task_name,
  83                                        OnceClosure closure,
  84                                        bool is_immediate) {
  85   // Wrapping a null closure in a critical closure has unclear semantics and
  86   // most likely indicates a bug. CHECK-ing early allows detecting and
  87   // investigating these cases more easily.
  88   CHECK(!closure.is_null());
  89   if (is_immediate) {
  90     return base::BindOnce(&internal::ImmediateCriticalClosure::Run,
  91                           Owned(new internal::ImmediateCriticalClosure(
  92                               task_name, std::move(closure))));
  93   } else {
  94     return base::BindOnce(&internal::PendingCriticalClosure::Run,
  95                           Owned(new internal::PendingCriticalClosure(
  96                               task_name, std::move(closure))));
  97   }
  98 }
  99
 100 inline OnceClosure MakeCriticalClosure(const Location& posted_from,
 101                                        OnceClosure closure,
 102                                        bool is_immediate) {
 103   return MakeCriticalClosure(posted_from.ToString(), std::move(closure),
 104                              is_immediate);
 105 }
 106
 107 #else  // BUILDFLAG(IS_IOS)
 108
 109 inline OnceClosure MakeCriticalClosure(StringPiece task_name,
 110                                        OnceClosure closure,
 111                                        bool is_immediate) {
 112   // No-op for platforms where the application does not need to acquire
 113   // background time for closures to finish when it goes into the background.
 114   return closure;
 115 }
 116
 117 inline OnceClosure MakeCriticalClosure(const Location& posted_from,
 118                                        OnceClosure closure,
 119                                        bool is_immediate) {
 120   return closure;
 121 }
 122
 123 #endif  // BUILDFLAG(IS_IOS)
 124
 125 }  // namespace base
 126
 127 #endif  // BASE_CRITICAL_CLOSURE_H_