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| 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 NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_ | |
| 6 #define NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_ | |
| 7 | |
| 8 #include <set> | |
| 9 | |
| 10 #include "base/memory/ref_counted.h" | |
| 11 #include "base/synchronization/lock.h" | |
| 12 #include "base/synchronization/waitable_event.h" | |
| 13 | |
| 14 namespace base { | |
| 15 class TaskRunner; | |
| 16 } // namespace base | |
| 17 | |
| 18 namespace disk_cache { | |
| 19 | |
| 20 class InFlightIO; | |
| 21 | |
| 22 // This class represents a single asynchronous IO operation while it is being | |
| 23 // bounced between threads. | |
| 24 class BackgroundIO : public base::RefCountedThreadSafe<BackgroundIO> { | |
| 25 public: | |
| 26 // Other than the actual parameters for the IO operation (including the | |
| 27 // |callback| that must be notified at the end), we need the controller that | |
| 28 // is keeping track of all operations. When done, we notify the controller | |
| 29 // (we do NOT invoke the callback), in the worker thead that completed the | |
| 30 // operation. | |
| 31 explicit BackgroundIO(InFlightIO* controller); | |
| 32 | |
| 33 // This method signals the controller that this operation is finished, in the | |
| 34 // original thread. In practice, this is a RunableMethod that allows | |
| 35 // cancellation. | |
| 36 void OnIOSignalled(); | |
| 37 | |
| 38 // Allows the cancellation of the task to notify the controller (step number 8 | |
| 39 // in the diagram below). In practice, if the controller waits for the | |
| 40 // operation to finish it doesn't have to wait for the final task to be | |
| 41 // processed by the message loop so calling this method prevents its delivery. | |
| 42 // Note that this method is not intended to cancel the actual IO operation or | |
| 43 // to prevent the first notification to take place (OnIOComplete). | |
| 44 void Cancel(); | |
| 45 | |
| 46 int result() { return result_; } | |
| 47 | |
| 48 base::WaitableEvent* io_completed() { | |
| 49 return &io_completed_; | |
| 50 } | |
| 51 | |
| 52 protected: | |
| 53 virtual ~BackgroundIO(); | |
| 54 | |
| 55 // Notifies the controller about the end of the operation, from the background | |
| 56 // thread. | |
| 57 void NotifyController(); | |
| 58 | |
| 59 int result_; // Final operation result. | |
| 60 | |
| 61 private: | |
| 62 friend class base::RefCountedThreadSafe<BackgroundIO>; | |
| 63 | |
| 64 // An event to signal when the operation completes. | |
| 65 base::WaitableEvent io_completed_; | |
| 66 InFlightIO* controller_; // The controller that tracks all operations. | |
| 67 base::Lock controller_lock_; // A lock protecting clearing of controller_. | |
| 68 | |
| 69 DISALLOW_COPY_AND_ASSIGN(BackgroundIO); | |
| 70 }; | |
| 71 | |
| 72 // This class keeps track of asynchronous IO operations. A single instance | |
| 73 // of this class is meant to be used to start an asynchronous operation (using | |
| 74 // PostXX, exposed by a derived class). This class will post the operation to a | |
| 75 // worker thread, hanlde the notification when the operation finishes and | |
| 76 // perform the callback on the same thread that was used to start the operation. | |
| 77 // | |
| 78 // The regular sequence of calls is: | |
| 79 // Thread_1 Worker_thread | |
| 80 // 1. DerivedInFlightIO::PostXX() | |
| 81 // 2. -> PostTask -> | |
| 82 // 3. InFlightIO::OnOperationPosted() | |
| 83 // 4. DerivedBackgroundIO::XX() | |
| 84 // 5. IO operation completes | |
| 85 // 6. InFlightIO::OnIOComplete() | |
| 86 // 7. <- PostTask <- | |
| 87 // 8. BackgroundIO::OnIOSignalled() | |
| 88 // 9. InFlightIO::InvokeCallback() | |
| 89 // 10. DerivedInFlightIO::OnOperationComplete() | |
| 90 // 11. invoke callback | |
| 91 // | |
| 92 // Shutdown is a special case that is handled though WaitForPendingIO() instead | |
| 93 // of just waiting for step 7. | |
| 94 class InFlightIO { | |
| 95 public: | |
| 96 InFlightIO(); | |
| 97 virtual ~InFlightIO(); | |
| 98 | |
| 99 // Blocks the current thread until all IO operations tracked by this object | |
| 100 // complete. | |
| 101 void WaitForPendingIO(); | |
| 102 | |
| 103 // Drops current pending operations without waiting for them to complete. | |
| 104 void DropPendingIO(); | |
| 105 | |
| 106 // Called on a background thread when |operation| completes. | |
| 107 void OnIOComplete(BackgroundIO* operation); | |
| 108 | |
| 109 // Invokes the users' completion callback at the end of the IO operation. | |
| 110 // |cancel_task| is true if the actual task posted to the thread is still | |
| 111 // queued (because we are inside WaitForPendingIO), and false if said task is | |
| 112 // the one performing the call. | |
| 113 void InvokeCallback(BackgroundIO* operation, bool cancel_task); | |
| 114 | |
| 115 protected: | |
| 116 // This method is called to signal the completion of the |operation|. |cancel| | |
| 117 // is true if the operation is being cancelled. This method is called on the | |
| 118 // thread that created this object. | |
| 119 virtual void OnOperationComplete(BackgroundIO* operation, bool cancel) = 0; | |
| 120 | |
| 121 // Signals this object that the derived class just posted the |operation| to | |
| 122 // be executed on a background thread. This method must be called on the same | |
| 123 // thread used to create this object. | |
| 124 void OnOperationPosted(BackgroundIO* operation); | |
| 125 | |
| 126 private: | |
| 127 typedef std::set<scoped_refptr<BackgroundIO> > IOList; | |
| 128 | |
| 129 IOList io_list_; // List of pending, in-flight io operations. | |
| 130 scoped_refptr<base::TaskRunner> callback_task_runner_; | |
| 131 | |
| 132 bool running_; // True after the first posted operation completes. | |
| 133 bool single_thread_; // True if we only have one thread. | |
| 134 | |
| 135 DISALLOW_COPY_AND_ASSIGN(InFlightIO); | |
| 136 }; | |
| 137 | |
| 138 } // namespace disk_cache | |
| 139 | |
| 140 #endif // NET_DISK_CACHE_BLOCKFILE_IN_FLIGHT_IO_H_ | |
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