#ifndef ANDROID_LOOPER_H
#define ANDROID_LOOPER_H
-#include <poll.h>
-
#ifdef __cplusplus
extern "C" {
#endif
typedef struct ALooper ALooper;
/**
- * For callback-based event loops, this is the prototype of the function
- * that is called. It is given the file descriptor it is associated with,
- * a bitmask of the poll events that were triggered (typically POLLIN), 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 ALooper_callbackFunc(int fd, int events, void* data);
-
-/**
- * Return the ALooper associated with the calling thread, or NULL if
+ * Returns the looper associated with the calling thread, or NULL if
* there is not one.
*/
ALooper* ALooper_forThread();
enum {
/**
- * Option for ALooper_prepare: this ALooper will accept calls to
+ * Option for ALooper_prepare: this looper will accept calls to
* ALooper_addFd() that do not have a callback (that is provide NULL
* for the callback). In this case the caller of ALooper_pollOnce()
* or ALooper_pollAll() MUST check the return from these functions to
};
/**
- * Prepare an ALooper associated with the calling thread, and return it.
- * If the thread already has an ALooper, it is returned. Otherwise, a new
+ * 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 ALOOPER_PREPARE_ALLOW_NON_CALLBACKS or 0.
*/
-ALooper* ALooper_prepare(int32_t opts);
+ALooper* ALooper_prepare(int opts);
enum {
/**
- * Result from ALooper_pollOnce() and ALooper_pollAll(): one or
- * more callbacks were executed.
+ * Result from ALooper_pollOnce() and ALooper_pollAll():
+ * The poll was awoken using wake() before the timeout expired
+ * and no callbacks were executed and no other file descriptors were ready.
*/
- ALOOPER_POLL_CALLBACK = -1,
-
+ ALOOPER_POLL_WAKE = -1,
+
+ /**
+ * Result from ALooper_pollOnce() and ALooper_pollAll():
+ * One or more callbacks were executed.
+ */
+ ALOOPER_POLL_CALLBACK = -2,
+
/**
- * Result from ALooper_pollOnce() and ALooper_pollAll(): the
- * timeout expired.
+ * Result from ALooper_pollOnce() and ALooper_pollAll():
+ * The timeout expired.
*/
- ALOOPER_POLL_TIMEOUT = -2,
-
+ ALOOPER_POLL_TIMEOUT = -3,
+
/**
- * Result from ALooper_pollOnce() and ALooper_pollAll(): an error
- * occurred.
+ * Result from ALooper_pollOnce() and ALooper_pollAll():
+ * An error occurred.
*/
- ALOOPER_POLL_ERROR = -3,
+ ALOOPER_POLL_ERROR = -4,
};
/**
- * Wait for events to be available, with optional timeout in milliseconds.
+ * Acquire a reference on the given ALooper object. This prevents the object
+ * from being deleted until the reference is removed. This is only needed
+ * to safely hand an ALooper from one thread to another.
+ */
+void ALooper_acquire(ALooper* looper);
+
+/**
+ * Remove a reference that was previously acquired with ALooper_acquire().
+ */
+void ALooper_release(ALooper* looper);
+
+/**
+ * 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.
+ */
+ ALOOPER_EVENT_INPUT = 1 << 0,
+
+ /**
+ * The file descriptor is available for write operations.
+ */
+ ALOOPER_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.
+ */
+ ALOOPER_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.
+ */
+ ALOOPER_EVENT_HANGUP = 1 << 3,
+};
+
+/**
+ * For callback-based event loops, this is the prototype of the function
+ * that is called. 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.
+ */
+typedef int (*ALooper_callbackFunc)(int fd, int events, void* data);
+
+/**
+ * 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 ALOOPER_POLL_CALLBACK if a callback was invoked.
+ * Returns ALOOPER_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 ALOOPER_POLL_CALLBACK if one or more callbacks were invoked.
*
* Returns ALOOPER_POLL_TIMEOUT if there was no data before the given
* timeout expired.
*
- * Returns ALOPER_POLL_ERROR if an error occurred.
+ * Returns ALOOPER_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 outEvents and outData will contain the poll
- * events and data associated with the fd.
+ * 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.
*/
-int32_t ALooper_pollOnce(int timeoutMillis, int* outEvents, void** outData);
+int ALooper_pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData);
/**
* Like ALooper_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 ALOOPER_POLL_CALLBACK.
*/
-int32_t ALooper_pollAll(int timeoutMillis, int* outEvents, void** outData);
-
-/**
- * Acquire a reference on the given ALooper object. This prevents the object
- * from being deleted until the reference is removed. This is only needed
- * to safely hand an ALooper from one thread to another.
- */
-void ALooper_acquire(ALooper* looper);
+int ALooper_pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData);
/**
- * Remove a reference that was previously acquired with ALooper_acquire().
+ * Wakes the poll asynchronously.
+ *
+ * This method can be called on any thread.
+ * This method returns immediately.
*/
-void ALooper_release(ALooper* looper);
+void ALooper_wake(ALooper* looper);
/**
- * Add a new file descriptor to be polled by the looper. If the same file
- * descriptor was previously added, it is replaced.
+ * 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
- * ALooper_pollOnce(). 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 POLLIN.
- * "callback" is the function to call when there is an event on the file
- * descriptor.
+ * "ident" is an identifier for this event, which is returned from ALooper_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.
* "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.
+ * (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 ALooper_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 or -1 if an error occurred.
+ *
+ * This method can be called on any thread.
+ * This method may block briefly if it needs to wake the poll.
*/
void ALooper_addFd(ALooper* looper, int fd, int ident, int events,
- ALooper_callbackFunc* callback, void* data);
+ ALooper_callbackFunc callback, void* data);
/**
- * Remove a previously added file descriptor from the looper.
+ * 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.
+ *
+ * Returns 1 if the file descriptor was removed, 0 if none was previously registered
+ * or -1 if an error occurred.
+ *
+ * This method can be called on any thread.
+ * This method may block briefly if it needs to wake the poll.
*/
-int32_t ALooper_removeFd(ALooper* looper, int fd);
+int ALooper_removeFd(ALooper* looper, int fd);
#ifdef __cplusplus
};