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Support looper callbacks based on smart pointers. 

Bug: 6559630
Change-Id: I5a667f219f431838638acefbc9fa6afa610971bd
This commit is contained in:
Jeff Brown 2012-05-31 16:15:35 -07:00
parent 588d5c8280
commit af567f73ac
2 changed files with 88 additions and 14 deletions
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54
include/utils/Looper.h
View File

@ -70,6 +70,9 @@ public:
* 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);
@ -79,6 +82,43 @@ private:
};
/**
* 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 ALOOPER_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 ALooper_callbackFunc function pointer.
*/
class SimpleLooperCallback : public LooperCallback {
protected:
virtual ~SimpleLooperCallback();
public:
SimpleLooperCallback(ALooper_callbackFunc callback);
virtual int handleEvent(int fd, int events, void* data);
private:
ALooper_callbackFunc mCallback;
};
/**
* A polling loop that supports monitoring file descriptor events, optionally
* using callbacks. The implementation uses epoll() internally.
@ -159,7 +199,7 @@ public:
* 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 ALooper_pollOnce().
* "ident" is an identifier for this event, which is returned from pollOnce().
* The identifier must be >= 0, or ALOOPER_POLL_CALLBACK if providing a non-NULL callback.
* "events" are the poll events to wake up on. Typically this is ALOOPER_EVENT_INPUT.
* "callback" is the function to call when there is an event on the file descriptor.
@ -179,8 +219,14 @@ public:
*
* 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, ALooper_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.
@ -193,6 +239,10 @@ public:
* 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.
@ -273,7 +323,7 @@ private:
struct Request {
int fd;
int ident;
ALooper_callbackFunc callback;
sp<LooperCallback> callback;
void* data;
};

48
libs/utils/Looper.cpp
View File

@ -30,6 +30,9 @@ WeakMessageHandler::WeakMessageHandler(const wp<MessageHandler>& handler) :
mHandler(handler) {
}
WeakMessageHandler::~WeakMessageHandler() {
}
void WeakMessageHandler::handleMessage(const Message& message) {
sp<MessageHandler> handler = mHandler.promote();
if (handler != NULL) {
@ -38,6 +41,20 @@ void WeakMessageHandler::handleMessage(const Message& message) {
}
// --- SimpleLooperCallback ---
SimpleLooperCallback::SimpleLooperCallback(ALooper_callbackFunc callback) :
mCallback(callback) {
}
SimpleLooperCallback::~SimpleLooperCallback() {
}
int SimpleLooperCallback::handleEvent(int fd, int events, void* data) {
return mCallback(fd, events, data);
}
// --- Looper ---
// Hint for number of file descriptors to be associated with the epoll instance.
@ -142,9 +159,8 @@ int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outDa
for (;;) {
while (mResponseIndex < mResponses.size()) {
const Response& response = mResponses.itemAt(mResponseIndex++);
ALooper_callbackFunc callback = response.request.callback;
if (!callback) {
int ident = response.request.ident;
int ident = response.request.ident;
if (ident >= 0) {
int fd = response.request.fd;
int events = response.events;
void* data = response.request.data;
@ -165,7 +181,7 @@ int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outDa
ALOGD("%p ~ pollOnce - returning result %d", this, result);
#endif
if (outFd != NULL) *outFd = 0;
if (outEvents != NULL) *outEvents = NULL;
if (outEvents != NULL) *outEvents = 0;
if (outData != NULL) *outData = NULL;
return result;
}
@ -293,20 +309,22 @@ Done: ;
// Invoke all response callbacks.
for (size_t i = 0; i < mResponses.size(); i++) {
const Response& response = mResponses.itemAt(i);
ALooper_callbackFunc callback = response.request.callback;
if (callback) {
Response& response = mResponses.editItemAt(i);
if (response.request.ident == ALOOPER_POLL_CALLBACK) {
int fd = response.request.fd;
int events = response.events;
void* data = response.request.data;
#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
ALOGD("%p ~ pollOnce - invoking fd event callback %p: fd=%d, events=0x%x, data=%p",
this, callback, fd, events, data);
this, response.request.callback.get(), fd, events, data);
#endif
int callbackResult = callback(fd, events, data);
int callbackResult = response.request.callback->handleEvent(fd, events, data);
if (callbackResult == 0) {
removeFd(fd);
}
// Clear the callback reference in the response structure promptly because we
// will not clear the response vector itself until the next poll.
response.request.callback.clear();
result = ALOOPER_POLL_CALLBACK;
}
}
@ -376,21 +394,27 @@ void Looper::pushResponse(int events, const Request& request) {
}
int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data) {
return addFd(fd, ident, events, callback ? new SimpleLooperCallback(callback) : NULL, data);
}
int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data) {
#if DEBUG_CALLBACKS
ALOGD("%p ~ addFd - fd=%d, ident=%d, events=0x%x, callback=%p, data=%p", this, fd, ident,
events, callback, data);
events, callback.get(), data);
#endif
if (! callback) {
if (!callback.get()) {
if (! mAllowNonCallbacks) {
ALOGE("Invalid attempt to set NULL callback but not allowed for this looper.");
return -1;
}
if (ident < 0) {
ALOGE("Invalid attempt to set NULL callback with ident <= 0.");
ALOGE("Invalid attempt to set NULL callback with ident < 0.");
return -1;
}
} else {
ident = ALOOPER_POLL_CALLBACK;
}
int epollEvents = 0;