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Diffstat (limited to 'include/utils/PollLoop.h')
-rw-r--r-- | include/utils/PollLoop.h | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/include/utils/PollLoop.h b/include/utils/PollLoop.h new file mode 100644 index 0000000..2ec39fe --- /dev/null +++ b/include/utils/PollLoop.h @@ -0,0 +1,137 @@ +/* + * Copyright (C) 2010 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifndef UTILS_POLL_LOOP_H +#define UTILS_POLL_LOOP_H + +#include <utils/Vector.h> +#include <utils/threads.h> + +#include <poll.h> + +namespace android { + +/** + * A basic file descriptor polling loop based on poll() with callbacks. + */ +class PollLoop : public RefBase { +protected: + virtual ~PollLoop(); + +public: + PollLoop(); + + /** + * A callback that it to be invoked when an event occurs on a file descriptor. + * Specifies the events that were triggered and the user data provided when the + * callback was set. + * + * Returns true if the callback should be kept, false if it should be removed automatically + * after the callback returns. + */ + typedef bool (*Callback)(int fd, int events, void* data); + + /** + * Performs a single call to poll() with optional timeout in milliseconds. + * Invokes callbacks for all file descriptors on which an event occurred. + * + * If the timeout is zero, returns immediately without blocking. + * If the timeout is negative, waits indefinitely until awoken. + * + * Returns true if a callback was invoked or if the loop was awoken by wake(). + * Returns false if a timeout or error occurred. + * + * This method must only be called on the main thread. + * This method blocks until either a file descriptor is signalled, a timeout occurs, + * or wake() is called. + * This method does not return until it has finished invoking the appropriate callbacks + * for all file descriptors that were signalled. + */ + bool pollOnce(int timeoutMillis); + + /** + * Wakes the loop asynchronously. + * + * This method can be called on any thread. + * This method returns immediately. + */ + void wake(); + + /** + * Sets the callback for a file descriptor, replacing the existing one, if any. + * It is an error to call this method with events == 0 or callback == NULL. + * + * Note that a callback can be invoked with the POLLERR, POLLHUP or POLLNVAL events + * even if it is not explicitly requested when registered. + * + * This method can be called on any thread. + * This method may block briefly if it needs to wake the poll loop. + */ + void setCallback(int fd, int events, Callback callback, void* data = NULL); + + /** + * Removes the callback for a file descriptor, if one exists. + * + * When this method returns, it is safe to close the file descriptor since the poll loop + * will no longer have a reference to it. However, it is possible for the callback to + * already be running or for it to run one last time if the file descriptor was already + * signalled. Calling code is responsible for ensuring that this case is safely handled. + * For example, if the callback takes care of removing itself during its own execution either + * by returning false or calling this method, then it can be guaranteed to not be invoked + * again at any later time unless registered anew. + * + * This method can be called on any thread. + * This method may block briefly if it needs to wake the poll loop. + * + * Returns true if a callback was actually removed, false if none was registered. + */ + bool removeCallback(int fd); + +private: + struct RequestedCallback { + Callback callback; + void* data; + }; + + struct PendingCallback { + int fd; + int events; + Callback callback; + void* data; + }; + + Mutex mLock; + Condition mAwake; + bool mPolling; + + int mWakeReadPipeFd; + int mWakeWritePipeFd; + + Vector<struct pollfd> mRequestedFds; + Vector<RequestedCallback> mRequestedCallbacks; + + Vector<PendingCallback> mPendingCallbacks; // used privately by pollOnce + + void openWakePipe(); + void closeWakePipe(); + + ssize_t getRequestIndexLocked(int fd); + void wakeAndLock(); +}; + +} // namespace android + +#endif // UTILS_POLL_LOOP_H |