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Diffstat (limited to 'libshims/include/utils/Looper.h')
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diff --git a/libshims/include/utils/Looper.h b/libshims/include/utils/Looper.h new file mode 100644 index 0000000..88e13cf --- /dev/null +++ b/libshims/include/utils/Looper.h @@ -0,0 +1,478 @@ +/* + * 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_LOOPER_H +#define UTILS_LOOPER_H + +#include <utils/threads.h> +#include <utils/RefBase.h> +#include <utils/KeyedVector.h> +#include <utils/Timers.h> + +#include <sys/epoll.h> + +namespace android { + +/* + * NOTE: Since Looper is used to implement the NDK ALooper, the Looper + * enums and the signature of Looper_callbackFunc need to align with + * that implementation. + */ + +/** + * For callback-based event loops, this is the prototype of the function + * that is called when a file descriptor event occurs. + * It is given the file descriptor it is associated with, + * a bitmask of the poll events that were triggered (typically EVENT_INPUT), + * and the data pointer that was originally supplied. + * + * Implementations should return 1 to continue receiving callbacks, or 0 + * to have this file descriptor and callback unregistered from the looper. + */ +typedef int (*Looper_callbackFunc)(int fd, int events, void* data); + +/** + * A message that can be posted to a Looper. + */ +struct Message { + Message() : what(0) { } + Message(int what) : what(what) { } + + /* The message type. (interpretation is left up to the handler) */ + int what; +}; + + +/** + * Interface for a Looper message handler. + * + * The Looper holds a strong reference to the message handler whenever it has + * a message to deliver to it. Make sure to call Looper::removeMessages + * to remove any pending messages destined for the handler so that the handler + * can be destroyed. + */ +class MessageHandler : public virtual RefBase { +protected: + virtual ~MessageHandler() { } + +public: + /** + * Handles a message. + */ + virtual void handleMessage(const Message& message) = 0; +}; + + +/** + * A simple proxy that holds a weak reference to a message handler. + */ +class WeakMessageHandler : public MessageHandler { +protected: + virtual ~WeakMessageHandler(); + +public: + WeakMessageHandler(const wp<MessageHandler>& handler); + virtual void handleMessage(const Message& message); + +private: + wp<MessageHandler> mHandler; +}; + + +/** + * A looper callback. + */ +class LooperCallback : public virtual RefBase { +protected: + virtual ~LooperCallback() { } + +public: + /** + * Handles a poll event for the given file descriptor. + * It is given the file descriptor it is associated with, + * a bitmask of the poll events that were triggered (typically EVENT_INPUT), + * and the data pointer that was originally supplied. + * + * Implementations should return 1 to continue receiving callbacks, or 0 + * to have this file descriptor and callback unregistered from the looper. + */ + virtual int handleEvent(int fd, int events, void* data) = 0; +}; + +/** + * Wraps a Looper_callbackFunc function pointer. + */ +class SimpleLooperCallback : public LooperCallback { +protected: + virtual ~SimpleLooperCallback(); + +public: + SimpleLooperCallback(Looper_callbackFunc callback); + virtual int handleEvent(int fd, int events, void* data); + +private: + Looper_callbackFunc mCallback; +}; + +/** + * A polling loop that supports monitoring file descriptor events, optionally + * using callbacks. The implementation uses epoll() internally. + * + * A looper can be associated with a thread although there is no requirement that it must be. + */ +class Looper : public RefBase { +protected: + virtual ~Looper(); + +public: + enum { + /** + * Result from Looper_pollOnce() and Looper_pollAll(): + * The poll was awoken using wake() before the timeout expired + * and no callbacks were executed and no other file descriptors were ready. + */ + POLL_WAKE = -1, + + /** + * Result from Looper_pollOnce() and Looper_pollAll(): + * One or more callbacks were executed. + */ + POLL_CALLBACK = -2, + + /** + * Result from Looper_pollOnce() and Looper_pollAll(): + * The timeout expired. + */ + POLL_TIMEOUT = -3, + + /** + * Result from Looper_pollOnce() and Looper_pollAll(): + * An error occurred. + */ + POLL_ERROR = -4, + }; + + /** + * Flags for file descriptor events that a looper can monitor. + * + * These flag bits can be combined to monitor multiple events at once. + */ + enum { + /** + * The file descriptor is available for read operations. + */ + EVENT_INPUT = 1 << 0, + + /** + * The file descriptor is available for write operations. + */ + EVENT_OUTPUT = 1 << 1, + + /** + * The file descriptor has encountered an error condition. + * + * The looper always sends notifications about errors; it is not necessary + * to specify this event flag in the requested event set. + */ + EVENT_ERROR = 1 << 2, + + /** + * The file descriptor was hung up. + * For example, indicates that the remote end of a pipe or socket was closed. + * + * The looper always sends notifications about hangups; it is not necessary + * to specify this event flag in the requested event set. + */ + EVENT_HANGUP = 1 << 3, + + /** + * The file descriptor is invalid. + * For example, the file descriptor was closed prematurely. + * + * The looper always sends notifications about invalid file descriptors; it is not necessary + * to specify this event flag in the requested event set. + */ + EVENT_INVALID = 1 << 4, + }; + + enum { + /** + * Option for Looper_prepare: this looper will accept calls to + * Looper_addFd() that do not have a callback (that is provide NULL + * for the callback). In this case the caller of Looper_pollOnce() + * or Looper_pollAll() MUST check the return from these functions to + * discover when data is available on such fds and process it. + */ + PREPARE_ALLOW_NON_CALLBACKS = 1<<0 + }; + + /** + * Creates a looper. + * + * If allowNonCallbaks is true, the looper will allow file descriptors to be + * registered without associated callbacks. This assumes that the caller of + * pollOnce() is prepared to handle callback-less events itself. + */ + Looper(bool allowNonCallbacks); + + /** + * Returns whether this looper instance allows the registration of file descriptors + * using identifiers instead of callbacks. + */ + bool getAllowNonCallbacks() const; + + /** + * Waits for events to be available, 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 an event appears. + * + * Returns POLL_WAKE if the poll was awoken using wake() before + * the timeout expired and no callbacks were invoked and no other file + * descriptors were ready. + * + * Returns POLL_CALLBACK if one or more callbacks were invoked. + * + * Returns POLL_TIMEOUT if there was no data before the given + * timeout expired. + * + * Returns POLL_ERROR if an error occurred. + * + * Returns a value >= 0 containing an identifier if its file descriptor has data + * and it has no callback function (requiring the caller here to handle it). + * In this (and only this) case outFd, outEvents and outData will contain the poll + * events and data associated with the fd, otherwise they will be set to NULL. + * + * This method does not return until it has finished invoking the appropriate callbacks + * for all file descriptors that were signalled. + */ + int pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData); + inline int pollOnce(int timeoutMillis) { + return pollOnce(timeoutMillis, NULL, NULL, NULL); + } + + /** + * Like pollOnce(), but performs all pending callbacks until all + * data has been consumed or a file descriptor is available with no callback. + * This function will never return POLL_CALLBACK. + */ + int pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData); + inline int pollAll(int timeoutMillis) { + return pollAll(timeoutMillis, NULL, NULL, NULL); + } + + /** + * Wakes the poll asynchronously. + * + * This method can be called on any thread. + * This method returns immediately. + */ + void wake(); + + /** + * Adds a new file descriptor to be polled by the looper. + * If the same file descriptor was previously added, it is replaced. + * + * "fd" is the file descriptor to be added. + * "ident" is an identifier for this event, which is returned from pollOnce(). + * The identifier must be >= 0, or POLL_CALLBACK if providing a non-NULL callback. + * "events" are the poll events to wake up on. Typically this is EVENT_INPUT. + * "callback" is the function to call when there is an event on the file descriptor. + * "data" is a private data pointer to supply to the callback. + * + * There are two main uses of this function: + * + * (1) If "callback" is non-NULL, then this function will be called when there is + * data on the file descriptor. It should execute any events it has pending, + * appropriately reading from the file descriptor. The 'ident' is ignored in this case. + * + * (2) If "callback" is NULL, the 'ident' will be returned by Looper_pollOnce + * when its file descriptor has data available, requiring the caller to take + * care of processing it. + * + * Returns 1 if the file descriptor was added, 0 if the arguments were invalid. + * + * This method can be called on any thread. + * This method may block briefly if it needs to wake the poll. + * + * The callback may either be specified as a bare function pointer or as a smart + * pointer callback object. The smart pointer should be preferred because it is + * easier to avoid races when the callback is removed from a different thread. + * See removeFd() for details. + */ + int addFd(int fd, int ident, int events, Looper_callbackFunc callback, void* data); + int addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data); + + /** + * Removes a previously added file descriptor from the looper. + * + * When this method returns, it is safe to close the file descriptor since the looper + * 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 0 or by calling this method, then it can be guaranteed to not be invoked + * again at any later time unless registered anew. + * + * A simple way to avoid this problem is to use the version of addFd() that takes + * a sp<LooperCallback> instead of a bare function pointer. The LooperCallback will + * be released at the appropriate time by the Looper. + * + * Returns 1 if the file descriptor was removed, 0 if none was previously registered. + * + * This method can be called on any thread. + * This method may block briefly if it needs to wake the poll. + */ + int removeFd(int fd); + + /** + * Enqueues a message to be processed by the specified handler. + * + * The handler must not be null. + * This method can be called on any thread. + */ + void sendMessage(const sp<MessageHandler>& handler, const Message& message); + + /** + * Enqueues a message to be processed by the specified handler after all pending messages + * after the specified delay. + * + * The time delay is specified in uptime nanoseconds. + * The handler must not be null. + * This method can be called on any thread. + */ + void sendMessageDelayed(nsecs_t uptimeDelay, const sp<MessageHandler>& handler, + const Message& message); + + /** + * Enqueues a message to be processed by the specified handler after all pending messages + * at the specified time. + * + * The time is specified in uptime nanoseconds. + * The handler must not be null. + * This method can be called on any thread. + */ + void sendMessageAtTime(nsecs_t uptime, const sp<MessageHandler>& handler, + const Message& message); + + /** + * Removes all messages for the specified handler from the queue. + * + * The handler must not be null. + * This method can be called on any thread. + */ + void removeMessages(const sp<MessageHandler>& handler); + + /** + * Removes all messages of a particular type for the specified handler from the queue. + * + * The handler must not be null. + * This method can be called on any thread. + */ + void removeMessages(const sp<MessageHandler>& handler, int what); + + /** + * Returns whether this looper's thread is currently polling for more work to do. + * This is a good signal that the loop is still alive rather than being stuck + * handling a callback. Note that this method is intrinsically racy, since the + * state of the loop can change before you get the result back. + */ + bool isPolling() const; + + /** + * Prepares a looper associated with the calling thread, and returns it. + * If the thread already has a looper, it is returned. Otherwise, a new + * one is created, associated with the thread, and returned. + * + * The opts may be PREPARE_ALLOW_NON_CALLBACKS or 0. + */ + static sp<Looper> prepare(int opts); + + /** + * Sets the given looper to be associated with the calling thread. + * If another looper is already associated with the thread, it is replaced. + * + * If "looper" is NULL, removes the currently associated looper. + */ + static void setForThread(const sp<Looper>& looper); + + /** + * Returns the looper associated with the calling thread, or NULL if + * there is not one. + */ + static sp<Looper> getForThread(); + +private: + struct Request { + int fd; + int ident; + sp<LooperCallback> callback; + void* data; + }; + + struct Response { + int events; + Request request; + }; + + struct MessageEnvelope { + MessageEnvelope() : uptime(0) { } + + MessageEnvelope(nsecs_t uptime, const sp<MessageHandler> handler, + const Message& message) : uptime(uptime), handler(handler), message(message) { + } + + nsecs_t uptime; + sp<MessageHandler> handler; + Message message; + }; + + const bool mAllowNonCallbacks; // immutable + + int mWakeReadPipeFd; // immutable + int mWakeWritePipeFd; // immutable + Mutex mLock; + + Vector<MessageEnvelope> mMessageEnvelopes; // guarded by mLock + bool mSendingMessage; // guarded by mLock + + // Whether we are currently waiting for work. Not protected by a lock, + // any use of it is racy anyway. + volatile bool mPolling; + + int mEpollFd; // immutable + + // Locked list of file descriptor monitoring requests. + KeyedVector<int, Request> mRequests; // guarded by mLock + + // This state is only used privately by pollOnce and does not require a lock since + // it runs on a single thread. + Vector<Response> mResponses; + size_t mResponseIndex; + nsecs_t mNextMessageUptime; // set to LLONG_MAX when none + + int pollInner(int timeoutMillis); + void awoken(); + void pushResponse(int events, const Request& request); + + static void initTLSKey(); + static void threadDestructor(void *st); +}; + +} // namespace android + +#endif // UTILS_LOOPER_H
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