Support looper callbacks based on smart pointers.
Bug: 6559630
Change-Id: I5a667f219f431838638acefbc9fa6afa610971bd
diff --git a/include/utils/Looper.h b/include/utils/Looper.h
index 84e3864..d4a0067 100644
--- a/include/utils/Looper.h
+++ b/include/utils/Looper.h
@@ -70,6 +70,9 @@
* 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);
@@ -80,6 +83,43 @@
/**
+ * 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 @@
* 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 @@
*
* 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 @@
* 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 @@
struct Request {
int fd;
int ident;
- ALooper_callbackFunc callback;
+ sp<LooperCallback> callback;
void* data;
};
diff --git a/libs/utils/Looper.cpp b/libs/utils/Looper.cpp
index 9894993..a5e6645 100644
--- a/libs/utils/Looper.cpp
+++ b/libs/utils/Looper.cpp
@@ -30,6 +30,9 @@
mHandler(handler) {
}
+WeakMessageHandler::~WeakMessageHandler() {
+}
+
void WeakMessageHandler::handleMessage(const Message& message) {
sp<MessageHandler> handler = mHandler.promote();
if (handler != NULL) {
@@ -38,6 +41,20 @@
}
+// --- 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 @@
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 @@
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 @@
// 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 @@
}
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;