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