271 lines
9.6 KiB
C
271 lines
9.6 KiB
C
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/*
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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_LOOPER_H
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#define UTILS_LOOPER_H
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#include <utils/threads.h>
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#include <utils/RefBase.h>
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#include <utils/KeyedVector.h>
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#include <utils/Timers.h>
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#include <android/looper.h>
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// When defined, uses epoll_wait() for polling, otherwise uses poll().
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#define LOOPER_USES_EPOLL
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// When defined, logs performance statistics for tuning and debugging purposes.
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//#define LOOPER_STATISTICS
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#ifdef LOOPER_USES_EPOLL
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#include <sys/epoll.h>
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#else
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#include <sys/poll.h>
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#endif
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/*
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* Declare a concrete type for the NDK's looper forward declaration.
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*/
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struct ALooper {
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};
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namespace android {
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/**
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* A polling loop that supports monitoring file descriptor events, optionally
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* using callbacks. The implementation uses epoll() internally.
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*
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* A looper can be associated with a thread although there is no requirement that it must be.
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*/
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class Looper : public ALooper, public RefBase {
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protected:
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virtual ~Looper();
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public:
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/**
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* Creates a looper.
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*
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* If allowNonCallbaks is true, the looper will allow file descriptors to be
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* registered without associated callbacks. This assumes that the caller of
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* pollOnce() is prepared to handle callback-less events itself.
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*/
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Looper(bool allowNonCallbacks);
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/**
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* Returns whether this looper instance allows the registration of file descriptors
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* using identifiers instead of callbacks.
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*/
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bool getAllowNonCallbacks() const;
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/**
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* Waits for events to be available, 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 an event appears.
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*
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* Returns ALOOPER_POLL_WAKE if the poll was awoken using wake() before
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* the timeout expired and no callbacks were invoked and no other file
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* descriptors were ready.
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*
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* Returns ALOOPER_POLL_CALLBACK if one or more callbacks were invoked.
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*
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* Returns ALOOPER_POLL_TIMEOUT if there was no data before the given
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* timeout expired.
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*
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* Returns ALOOPER_POLL_ERROR if an error occurred.
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*
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* Returns a value >= 0 containing an identifier if its file descriptor has data
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* and it has no callback function (requiring the caller here to handle it).
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* In this (and only this) case outFd, outEvents and outData will contain the poll
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* events and data associated with the fd, otherwise they will be set to NULL.
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*
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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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int pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData);
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inline int pollOnce(int timeoutMillis) {
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return pollOnce(timeoutMillis, NULL, NULL, NULL);
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}
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/**
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* Like pollOnce(), but performs all pending callbacks until all
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* data has been consumed or a file descriptor is available with no callback.
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* This function will never return ALOOPER_POLL_CALLBACK.
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*/
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int pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData);
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inline int pollAll(int timeoutMillis) {
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return pollAll(timeoutMillis, NULL, NULL, NULL);
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}
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/**
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* Wakes the poll 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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* Adds a new file descriptor to be polled by the looper.
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* If the same file descriptor was previously added, it is replaced.
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*
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* "fd" is the file descriptor to be added.
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* "ident" is an identifier for this event, which is returned from ALooper_pollOnce().
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* The identifier must be >= 0, or ALOOPER_POLL_CALLBACK if providing a non-NULL callback.
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* "events" are the poll events to wake up on. Typically this is ALOOPER_EVENT_INPUT.
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* "callback" is the function to call when there is an event on the file descriptor.
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* "data" is a private data pointer to supply to the callback.
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*
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* There are two main uses of this function:
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*
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* (1) If "callback" is non-NULL, then this function will be called when there is
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* data on the file descriptor. It should execute any events it has pending,
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* appropriately reading from the file descriptor. The 'ident' is ignored in this case.
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*
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* (2) If "callback" is NULL, the 'ident' will be returned by ALooper_pollOnce
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* when its file descriptor has data available, requiring the caller to take
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* care of processing it.
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*
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* Returns 1 if the file descriptor was added, 0 if the arguments were invalid.
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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.
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*/
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int addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data);
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/**
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* Removes a previously added file descriptor from the looper.
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*
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* When this method returns, it is safe to close the file descriptor since the looper
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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 0 or by 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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* Returns 1 if the file descriptor was removed, 0 if none was previously 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.
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*/
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int removeFd(int fd);
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/**
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* Prepares a looper associated with the calling thread, and returns it.
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* If the thread already has a looper, it is returned. Otherwise, a new
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* one is created, associated with the thread, and returned.
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*
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* The opts may be ALOOPER_PREPARE_ALLOW_NON_CALLBACKS or 0.
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*/
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static sp<Looper> prepare(int opts);
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/**
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* Sets the given looper to be associated with the calling thread.
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* If another looper is already associated with the thread, it is replaced.
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*
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* If "looper" is NULL, removes the currently associated looper.
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*/
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static void setForThread(const sp<Looper>& looper);
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/**
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* Returns the looper associated with the calling thread, or NULL if
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* there is not one.
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*/
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static sp<Looper> getForThread();
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private:
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struct Request {
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int fd;
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int ident;
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ALooper_callbackFunc callback;
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void* data;
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};
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struct Response {
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int events;
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Request request;
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};
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const bool mAllowNonCallbacks; // immutable
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int mWakeReadPipeFd; // immutable
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int mWakeWritePipeFd; // immutable
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Mutex mLock;
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#ifdef LOOPER_USES_EPOLL
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int mEpollFd; // immutable
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// Locked list of file descriptor monitoring requests.
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KeyedVector<int, Request> mRequests; // guarded by mLock
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#else
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// The lock guards state used to track whether there is a poll() in progress and whether
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// there are any other threads waiting in wakeAndLock(). The condition variables
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// are used to transfer control among these threads such that all waiters are
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// serviced before a new poll can begin.
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// The wakeAndLock() method increments mWaiters, wakes the poll, blocks on mAwake
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// until mPolling becomes false, then decrements mWaiters again.
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// The poll() method blocks on mResume until mWaiters becomes 0, then sets
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// mPolling to true, blocks until the poll completes, then resets mPolling to false
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// and signals mResume if there are waiters.
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bool mPolling; // guarded by mLock
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uint32_t mWaiters; // guarded by mLock
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Condition mAwake; // guarded by mLock
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Condition mResume; // guarded by mLock
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Vector<struct pollfd> mRequestedFds; // must hold mLock and mPolling must be false to modify
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Vector<Request> mRequests; // must hold mLock and mPolling must be false to modify
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ssize_t getRequestIndexLocked(int fd);
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void wakeAndLock();
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#endif
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#ifdef LOOPER_STATISTICS
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static const int SAMPLED_WAKE_CYCLES_TO_AGGREGATE = 100;
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static const int SAMPLED_POLLS_TO_AGGREGATE = 1000;
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nsecs_t mPendingWakeTime;
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int mPendingWakeCount;
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int mSampledWakeCycles;
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int mSampledWakeCountSum;
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nsecs_t mSampledWakeLatencySum;
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int mSampledPolls;
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int mSampledZeroPollCount;
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int mSampledZeroPollLatencySum;
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int mSampledTimeoutPollCount;
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int mSampledTimeoutPollLatencySum;
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#endif
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// This state is only used privately by pollOnce and does not require a lock since
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// it runs on a single thread.
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Vector<Response> mResponses;
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size_t mResponseIndex;
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int pollInner(int timeoutMillis);
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void awoken();
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void pushResponse(int events, const Request& request);
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static void initTLSKey();
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static void threadDestructor(void *st);
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};
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} // namespace android
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#endif // UTILS_LOOPER_H
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