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Side by Side Diff: net/disk_cache/blockfile/in_flight_io.h

Issue 992733002: Remove //net (except for Android test stuff) and sdch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 9 months ago
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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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