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