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| 1 // Copyright 2016 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 BASE_FILES_FILE_DESCRIPTOR_WATCHER_POSIX_H_ |
| 6 #define BASE_FILES_FILE_DESCRIPTOR_WATCHER_POSIX_H_ |
| 7 |
| 8 #include <memory> |
| 9 |
| 10 #include "base/base_export.h" |
| 11 #include "base/callback.h" |
| 12 #include "base/macros.h" |
| 13 #include "base/memory/ref_counted.h" |
| 14 #include "base/memory/weak_ptr.h" |
| 15 #include "base/message_loop/message_loop.h" |
| 16 #include "base/sequence_checker.h" |
| 17 |
| 18 namespace base { |
| 19 |
| 20 class SingleThreadTaskRunner; |
| 21 |
| 22 // The FileDescriptorWatcher API allows callbacks to be invoked when file |
| 23 // descriptors are readable or writable without blocking. |
| 24 class BASE_EXPORT FileDescriptorWatcher { |
| 25 public: |
| 26 // Instantiated and returned by WatchReadable() or WatchWritable(). The |
| 27 // constructor registers a callback to be invoked when a file descriptor is |
| 28 // readable or writable without blocking and the destructor unregisters it. |
| 29 class Controller { |
| 30 public: |
| 31 // Unregisters the callback registered by the constructor. |
| 32 ~Controller(); |
| 33 |
| 34 private: |
| 35 friend class FileDescriptorWatcher; |
| 36 class Watcher; |
| 37 |
| 38 // Registers |callback| to be invoked when |fd| is readable or writable |
| 39 // without blocking (depending on |mode|). |
| 40 Controller(MessageLoopForIO::Mode mode, int fd, const Closure& callback); |
| 41 |
| 42 // Starts watching the file descriptor. |
| 43 void StartWatching(); |
| 44 |
| 45 // Runs |callback_|. |
| 46 void RunCallback(); |
| 47 |
| 48 // The callback to run when the watched file descriptor is readable or |
| 49 // writable without blocking. |
| 50 Closure callback_; |
| 51 |
| 52 // TaskRunner associated with the MessageLoopForIO that watches the file |
| 53 // descriptor. |
| 54 const scoped_refptr<SingleThreadTaskRunner> |
| 55 message_loop_for_io_task_runner_; |
| 56 |
| 57 // Notified by the MessageLoopForIO associated with |
| 58 // |message_loop_for_io_task_runner_| when the watched file descriptor is |
| 59 // readable or writable without blocking. Posts a task to run RunCallback() |
| 60 // on the sequence on which the Controller was instantiated. When the |
| 61 // Controller is deleted, ownership of |watcher_| is transfered to a delete |
| 62 // task posted to the MessageLoopForIO. This ensures that |watcher_| isn't |
| 63 // deleted while it is being used by the MessageLoopForIO. |
| 64 std::unique_ptr<Watcher> watcher_; |
| 65 |
| 66 // Validates that the Controller is used on the sequence on which it was |
| 67 // instantiated. |
| 68 SequenceChecker sequence_checker_; |
| 69 |
| 70 WeakPtrFactory<Controller> weak_factory_; |
| 71 |
| 72 DISALLOW_COPY_AND_ASSIGN(Controller); |
| 73 }; |
| 74 |
| 75 // Registers |message_loop_for_io| to watch file descriptors for which |
| 76 // callbacks are registered from the current thread via WatchReadable() or |
| 77 // WatchWritable(). |message_loop_for_io| may run on another thread. The |
| 78 // constructed FileDescriptorWatcher must not outlive |message_loop_for_io|. |
| 79 FileDescriptorWatcher(MessageLoopForIO* message_loop_for_io); |
| 80 ~FileDescriptorWatcher(); |
| 81 |
| 82 // Registers |callback| to be invoked on the current sequence when |fd| is |
| 83 // readable or writable without blocking. |callback| is unregistered when the |
| 84 // returned Controller is deleted (deletion must happen on the current |
| 85 // sequence). To call these methods, a FileDescriptorWatcher must have been |
| 86 // instantiated on the current thread and SequencedTaskRunnerHandle::IsSet() |
| 87 // must return true. |
| 88 static std::unique_ptr<Controller> WatchReadable(int fd, |
| 89 const Closure& callback); |
| 90 static std::unique_ptr<Controller> WatchWritable(int fd, |
| 91 const Closure& callback); |
| 92 |
| 93 private: |
| 94 DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher); |
| 95 }; |
| 96 |
| 97 } // namespace base |
| 98 |
| 99 #endif // BASE_FILES_FILE_DESCRIPTOR_WATCHER_POSIX_H_ |
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