libs/utils/Looper.cpp - platform/frameworks/base - Gitiles

 //
 // Copyright 2010 The Android Open Source Project
 //
 // A looper implementation based on epoll().
 //
 #define LOG_TAG "Looper"

 //#define LOG_NDEBUG 0

 // Debugs poll and wake interactions.
 #define DEBUG_POLL_AND_WAKE 0

 // Debugs callback registration and invocation.
 #define DEBUG_CALLBACKS 0

 #include <cutils/log.h>
 #include <utils/Looper.h>
 #include <utils/Timers.h>

 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/epoll.h>


 namespace android {

 // Hint for number of file descriptors to be associated with the epoll instance.
 static const int EPOLL_SIZE_HINT = 8;

 // Maximum number of file descriptors for which to retrieve poll events each iteration.
 static const int EPOLL_MAX_EVENTS = 16;

 static pthread_once_t gTLSOnce = PTHREAD_ONCE_INIT;
 static pthread_key_t gTLSKey = 0;

 Looper::Looper(bool allowNonCallbacks) :
         mAllowNonCallbacks(allowNonCallbacks),
         mResponseIndex(0) {
     mEpollFd = epoll_create(EPOLL_SIZE_HINT);
     LOG_ALWAYS_FATAL_IF(mEpollFd < 0, "Could not create epoll instance.  errno=%d", errno);

     int wakeFds[2];
     int result = pipe(wakeFds);
     LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe.  errno=%d", errno);

     mWakeReadPipeFd = wakeFds[0];
     mWakeWritePipeFd = wakeFds[1];

     result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);
     LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking.  errno=%d",
             errno);

     result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
     LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking.  errno=%d",
             errno);

     struct epoll_event eventItem;
     memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
     eventItem.events = EPOLLIN;
     eventItem.data.fd = mWakeReadPipeFd;
     result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, & eventItem);
     LOG_ALWAYS_FATAL_IF(result != 0, "Could not add wake read pipe to epoll instance.  errno=%d",
             errno);
 }

 Looper::~Looper() {
     close(mWakeReadPipeFd);
     close(mWakeWritePipeFd);
     close(mEpollFd);
 }

 void Looper::initTLSKey() {
     int result = pthread_key_create(& gTLSKey, threadDestructor);
     LOG_ALWAYS_FATAL_IF(result != 0, "Could not allocate TLS key.");
 }

 void Looper::threadDestructor(void *st) {
     Looper* const self = static_cast<Looper*>(st);
     if (self != NULL) {
         self->decStrong((void*)threadDestructor);
     }
 }

 void Looper::setForThread(const sp<Looper>& looper) {
     sp<Looper> old = getForThread(); // also has side-effect of initializing TLS

     if (looper != NULL) {
         looper->incStrong((void*)threadDestructor);
     }

     pthread_setspecific(gTLSKey, looper.get());

     if (old != NULL) {
         old->decStrong((void*)threadDestructor);
     }
 }

 sp<Looper> Looper::getForThread() {
     int result = pthread_once(& gTLSOnce, initTLSKey);
     LOG_ALWAYS_FATAL_IF(result != 0, "pthread_once failed");

     return (Looper*)pthread_getspecific(gTLSKey);
 }

 sp<Looper> Looper::prepare(int opts) {
     bool allowNonCallbacks = opts & ALOOPER_PREPARE_ALLOW_NON_CALLBACKS;
     sp<Looper> looper = Looper::getForThread();
     if (looper == NULL) {
         looper = new Looper(allowNonCallbacks);
         Looper::setForThread(looper);
     }
     if (looper->getAllowNonCallbacks() != allowNonCallbacks) {
         LOGW("Looper already prepared for this thread with a different value for the "
                 "ALOOPER_PREPARE_ALLOW_NON_CALLBACKS option.");
     }
     return looper;
 }

 bool Looper::getAllowNonCallbacks() const {
     return mAllowNonCallbacks;
 }

 int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
     int result = 0;
     for (;;) {
         while (mResponseIndex < mResponses.size()) {
             const Response& response = mResponses.itemAt(mResponseIndex++);
             if (! response.request.callback) {
 #if DEBUG_POLL_AND_WAKE
                 LOGD("%p ~ pollOnce - returning signalled identifier %d: "
                         "fd=%d, events=0x%x, data=%p", this,
                         response.request.ident, response.request.fd,
                         response.events, response.request.data);
 #endif
                 if (outFd != NULL) *outFd = response.request.fd;
                 if (outEvents != NULL) *outEvents = response.events;
                 if (outData != NULL) *outData = response.request.data;
                 return response.request.ident;
             }
         }

         if (result != 0) {
 #if DEBUG_POLL_AND_WAKE
             LOGD("%p ~ pollOnce - returning result %d", this, result);
 #endif
             if (outFd != NULL) *outFd = 0;
             if (outEvents != NULL) *outEvents = NULL;
             if (outData != NULL) *outData = NULL;
             return result;
         }

         result = pollInner(timeoutMillis);
     }
 }

 int Looper::pollInner(int timeoutMillis) {
 #if DEBUG_POLL_AND_WAKE
     LOGD("%p ~ pollOnce - waiting: timeoutMillis=%d", this, timeoutMillis);
 #endif
     struct epoll_event eventItems[EPOLL_MAX_EVENTS];
     int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
     if (eventCount < 0) {
         if (errno == EINTR) {
             return ALOOPER_POLL_WAKE;
         }

         LOGW("Poll failed with an unexpected error, errno=%d", errno);
         return ALOOPER_POLL_ERROR;
     }

     if (eventCount == 0) {
 #if DEBUG_POLL_AND_WAKE
         LOGD("%p ~ pollOnce - timeout", this);
 #endif
         return ALOOPER_POLL_TIMEOUT;
     }

     int result = ALOOPER_POLL_WAKE;
     mResponses.clear();
     mResponseIndex = 0;

 #if DEBUG_POLL_AND_WAKE
     LOGD("%p ~ pollOnce - handling events from %d fds", this, eventCount);
 #endif
     bool acquiredLock = false;
     for (int i = 0; i < eventCount; i++) {
         int fd = eventItems[i].data.fd;
         uint32_t epollEvents = eventItems[i].events;
         if (fd == mWakeReadPipeFd) {
             if (epollEvents & EPOLLIN) {
 #if DEBUG_POLL_AND_WAKE
                 LOGD("%p ~ pollOnce - awoken", this);
 #endif
                 char buffer[16];
                 ssize_t nRead;
                 do {
                     nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));
                 } while ((nRead == -1 && errno == EINTR) || nRead == sizeof(buffer));
             } else {
                 LOGW("Ignoring unexpected epoll events 0x%x on wake read pipe.", epollEvents);
             }
         } else {
             if (! acquiredLock) {
                 mLock.lock();
                 acquiredLock = true;
             }

             ssize_t requestIndex = mRequests.indexOfKey(fd);
             if (requestIndex >= 0) {
                 int events = 0;
                 if (epollEvents & EPOLLIN) events |= ALOOPER_EVENT_INPUT;
                 if (epollEvents & EPOLLOUT) events |= ALOOPER_EVENT_OUTPUT;
                 if (epollEvents & EPOLLERR) events |= ALOOPER_EVENT_ERROR;
                 if (epollEvents & EPOLLHUP) events |= ALOOPER_EVENT_HANGUP;

                 Response response;
                 response.events = events;
                 response.request = mRequests.valueAt(requestIndex);
                 mResponses.push(response);
             } else {
                 LOGW("Ignoring unexpected epoll events 0x%x on fd %d that is "
                         "no longer registered.", epollEvents, fd);
             }
         }
     }
     if (acquiredLock) {
         mLock.unlock();
     }

     for (size_t i = 0; i < mResponses.size(); i++) {
         const Response& response = mResponses.itemAt(i);
         if (response.request.callback) {
 #if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
             LOGD("%p ~ pollOnce - invoking callback: fd=%d, events=0x%x, data=%p", this,
                     response.request.fd, response.events, response.request.data);
 #endif
             int callbackResult = response.request.callback(
                     response.request.fd, response.events, response.request.data);
             if (callbackResult == 0) {
                 removeFd(response.request.fd);
             }

             result = ALOOPER_POLL_CALLBACK;
         }
     }
     return result;
 }

 int Looper::pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
     if (timeoutMillis <= 0) {
         int result;
         do {
             result = pollOnce(timeoutMillis, outFd, outEvents, outData);
         } while (result == ALOOPER_POLL_CALLBACK);
         return result;
     } else {
         nsecs_t endTime = systemTime(SYSTEM_TIME_MONOTONIC)
                 + milliseconds_to_nanoseconds(timeoutMillis);

         for (;;) {
             int result = pollOnce(timeoutMillis, outFd, outEvents, outData);
             if (result != ALOOPER_POLL_CALLBACK) {
                 return result;
             }

             nsecs_t timeoutNanos = endTime - systemTime(SYSTEM_TIME_MONOTONIC);
             if (timeoutNanos <= 0) {
                 return ALOOPER_POLL_TIMEOUT;
             }

             timeoutMillis = int(nanoseconds_to_milliseconds(timeoutNanos + 999999LL));
         }
     }
 }

 void Looper::wake() {
 #if DEBUG_POLL_AND_WAKE
     LOGD("%p ~ wake", this);
 #endif

     ssize_t nWrite;
     do {
         nWrite = write(mWakeWritePipeFd, "W", 1);
     } while (nWrite == -1 && errno == EINTR);

     if (nWrite != 1) {
         if (errno != EAGAIN) {
             LOGW("Could not write wake signal, errno=%d", errno);
         }
     }
 }

 int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data) {
 #if DEBUG_CALLBACKS
     LOGD("%p ~ addFd - fd=%d, ident=%d, events=0x%x, callback=%p, data=%p", this, fd, ident,
             events, callback, data);
 #endif

     int epollEvents = 0;
     if (events & ALOOPER_EVENT_INPUT) epollEvents |= EPOLLIN;
     if (events & ALOOPER_EVENT_OUTPUT) epollEvents |= EPOLLOUT;
     if (events & ALOOPER_EVENT_ERROR) epollEvents |= EPOLLERR;
     if (events & ALOOPER_EVENT_HANGUP) epollEvents |= EPOLLHUP;

     if (epollEvents == 0) {
         LOGE("Invalid attempt to set a callback with no selected poll events.");
         return -1;
     }

     if (! callback) {
         if (! mAllowNonCallbacks) {
             LOGE("Invalid attempt to set NULL callback but not allowed for this looper.");
             return -1;
         }

         if (ident < 0) {
             LOGE("Invalid attempt to set NULL callback with ident <= 0.");
             return -1;
         }
     }

     { // acquire lock
         AutoMutex _l(mLock);

         Request request;
         request.fd = fd;
         request.ident = ident;
         request.callback = callback;
         request.data = data;

         struct epoll_event eventItem;
         memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
         eventItem.events = epollEvents;
         eventItem.data.fd = fd;

         ssize_t requestIndex = mRequests.indexOfKey(fd);
         if (requestIndex < 0) {
             int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
             if (epollResult < 0) {
                 LOGE("Error adding epoll events for fd %d, errno=%d", fd, errno);
                 return -1;
             }
             mRequests.add(fd, request);
         } else {
             int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);
             if (epollResult < 0) {
                 LOGE("Error modifying epoll events for fd %d, errno=%d", fd, errno);
                 return -1;
             }
             mRequests.replaceValueAt(requestIndex, request);
         }
     } // release lock
     return 1;
 }

 int Looper::removeFd(int fd) {
 #if DEBUG_CALLBACKS
     LOGD("%p ~ removeFd - fd=%d", this, fd);
 #endif

     { // acquire lock
         AutoMutex _l(mLock);
         ssize_t requestIndex = mRequests.indexOfKey(fd);
         if (requestIndex < 0) {
             return 0;
         }

         int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_DEL, fd, NULL);
         if (epollResult < 0) {
             LOGE("Error removing epoll events for fd %d, errno=%d", fd, errno);
             return -1;
         }

         mRequests.removeItemsAt(requestIndex);
     } // request lock
     return 1;
 }

 } // namespace android
	//
	// Copyright 2010 The Android Open Source Project
	//
	// A looper implementation based on epoll().
	//
	#define LOG_TAG "Looper"

	//#define LOG_NDEBUG 0

	// Debugs poll and wake interactions.
	#define DEBUG_POLL_AND_WAKE 0

	// Debugs callback registration and invocation.
	#define DEBUG_CALLBACKS 0

	#include <cutils/log.h>
	#include <utils/Looper.h>
	#include <utils/Timers.h>

	#include <unistd.h>
	#include <fcntl.h>
	#include <sys/epoll.h>


	namespace android {

	// Hint for number of file descriptors to be associated with the epoll instance.
	static const int EPOLL_SIZE_HINT = 8;

	// Maximum number of file descriptors for which to retrieve poll events each iteration.
	static const int EPOLL_MAX_EVENTS = 16;

	static pthread_once_t gTLSOnce = PTHREAD_ONCE_INIT;
	static pthread_key_t gTLSKey = 0;

	Looper::Looper(bool allowNonCallbacks) :
	mAllowNonCallbacks(allowNonCallbacks),
	mResponseIndex(0) {
	mEpollFd = epoll_create(EPOLL_SIZE_HINT);
	LOG_ALWAYS_FATAL_IF(mEpollFd < 0, "Could not create epoll instance. errno=%d", errno);

	int wakeFds[2];
	int result = pipe(wakeFds);
	LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe. errno=%d", errno);

	mWakeReadPipeFd = wakeFds[0];
	mWakeWritePipeFd = wakeFds[1];

	result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);
	LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking. errno=%d",
	errno);

	result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
	LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking. errno=%d",
	errno);

	struct epoll_event eventItem;
	memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
	eventItem.events = EPOLLIN;
	eventItem.data.fd = mWakeReadPipeFd;
	result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, & eventItem);
	LOG_ALWAYS_FATAL_IF(result != 0, "Could not add wake read pipe to epoll instance. errno=%d",
	errno);
	}

	Looper::~Looper() {
	close(mWakeReadPipeFd);
	close(mWakeWritePipeFd);
	close(mEpollFd);
	}

	void Looper::initTLSKey() {
	int result = pthread_key_create(& gTLSKey, threadDestructor);
	LOG_ALWAYS_FATAL_IF(result != 0, "Could not allocate TLS key.");
	}

	void Looper::threadDestructor(void *st) {
	Looper* const self = static_cast<Looper*>(st);
	if (self != NULL) {
	self->decStrong((void*)threadDestructor);
	}
	}

	void Looper::setForThread(const sp<Looper>& looper) {
	sp<Looper> old = getForThread(); // also has side-effect of initializing TLS

	if (looper != NULL) {
	looper->incStrong((void*)threadDestructor);
	}

	pthread_setspecific(gTLSKey, looper.get());

	if (old != NULL) {
	old->decStrong((void*)threadDestructor);
	}
	}

	sp<Looper> Looper::getForThread() {
	int result = pthread_once(& gTLSOnce, initTLSKey);
	LOG_ALWAYS_FATAL_IF(result != 0, "pthread_once failed");

	return (Looper*)pthread_getspecific(gTLSKey);
	}

	sp<Looper> Looper::prepare(int opts) {
	bool allowNonCallbacks = opts & ALOOPER_PREPARE_ALLOW_NON_CALLBACKS;
	sp<Looper> looper = Looper::getForThread();
	if (looper == NULL) {
	looper = new Looper(allowNonCallbacks);
	Looper::setForThread(looper);
	}
	if (looper->getAllowNonCallbacks() != allowNonCallbacks) {
	LOGW("Looper already prepared for this thread with a different value for the "
	"ALOOPER_PREPARE_ALLOW_NON_CALLBACKS option.");
	}
	return looper;
	}

	bool Looper::getAllowNonCallbacks() const {
	return mAllowNonCallbacks;
	}

	int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
	int result = 0;
	for (;;) {
	while (mResponseIndex < mResponses.size()) {
	const Response& response = mResponses.itemAt(mResponseIndex++);
	if (! response.request.callback) {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - returning signalled identifier %d: "
	"fd=%d, events=0x%x, data=%p", this,
	response.request.ident, response.request.fd,
	response.events, response.request.data);
	#endif
	if (outFd != NULL) *outFd = response.request.fd;
	if (outEvents != NULL) *outEvents = response.events;
	if (outData != NULL) *outData = response.request.data;
	return response.request.ident;
	}
	}

	if (result != 0) {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - returning result %d", this, result);
	#endif
	if (outFd != NULL) *outFd = 0;
	if (outEvents != NULL) *outEvents = NULL;
	if (outData != NULL) *outData = NULL;
	return result;
	}

	result = pollInner(timeoutMillis);
	}
	}

	int Looper::pollInner(int timeoutMillis) {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - waiting: timeoutMillis=%d", this, timeoutMillis);
	#endif
	struct epoll_event eventItems[EPOLL_MAX_EVENTS];
	int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
	if (eventCount < 0) {
	if (errno == EINTR) {
	return ALOOPER_POLL_WAKE;
	}

	LOGW("Poll failed with an unexpected error, errno=%d", errno);
	return ALOOPER_POLL_ERROR;
	}

	if (eventCount == 0) {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - timeout", this);
	#endif
	return ALOOPER_POLL_TIMEOUT;
	}

	int result = ALOOPER_POLL_WAKE;
	mResponses.clear();
	mResponseIndex = 0;

	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - handling events from %d fds", this, eventCount);
	#endif
	bool acquiredLock = false;
	for (int i = 0; i < eventCount; i++) {
	int fd = eventItems[i].data.fd;
	uint32_t epollEvents = eventItems[i].events;
	if (fd == mWakeReadPipeFd) {
	if (epollEvents & EPOLLIN) {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ pollOnce - awoken", this);
	#endif
	char buffer[16];
	ssize_t nRead;
	do {
	nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));
	} while ((nRead == -1 && errno == EINTR) \|\| nRead == sizeof(buffer));
	} else {
	LOGW("Ignoring unexpected epoll events 0x%x on wake read pipe.", epollEvents);
	}
	} else {
	if (! acquiredLock) {
	mLock.lock();
	acquiredLock = true;
	}

	ssize_t requestIndex = mRequests.indexOfKey(fd);
	if (requestIndex >= 0) {
	int events = 0;
	if (epollEvents & EPOLLIN) events \|= ALOOPER_EVENT_INPUT;
	if (epollEvents & EPOLLOUT) events \|= ALOOPER_EVENT_OUTPUT;
	if (epollEvents & EPOLLERR) events \|= ALOOPER_EVENT_ERROR;
	if (epollEvents & EPOLLHUP) events \|= ALOOPER_EVENT_HANGUP;

	Response response;
	response.events = events;
	response.request = mRequests.valueAt(requestIndex);
	mResponses.push(response);
	} else {
	LOGW("Ignoring unexpected epoll events 0x%x on fd %d that is "
	"no longer registered.", epollEvents, fd);
	}
	}
	}
	if (acquiredLock) {
	mLock.unlock();
	}

	for (size_t i = 0; i < mResponses.size(); i++) {
	const Response& response = mResponses.itemAt(i);
	if (response.request.callback) {
	#if DEBUG_POLL_AND_WAKE \|\| DEBUG_CALLBACKS
	LOGD("%p ~ pollOnce - invoking callback: fd=%d, events=0x%x, data=%p", this,
	response.request.fd, response.events, response.request.data);
	#endif
	int callbackResult = response.request.callback(
	response.request.fd, response.events, response.request.data);
	if (callbackResult == 0) {
	removeFd(response.request.fd);
	}

	result = ALOOPER_POLL_CALLBACK;
	}
	}
	return result;
	}

	int Looper::pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
	if (timeoutMillis <= 0) {
	int result;
	do {
	result = pollOnce(timeoutMillis, outFd, outEvents, outData);
	} while (result == ALOOPER_POLL_CALLBACK);
	return result;
	} else {
	nsecs_t endTime = systemTime(SYSTEM_TIME_MONOTONIC)
	+ milliseconds_to_nanoseconds(timeoutMillis);

	for (;;) {
	int result = pollOnce(timeoutMillis, outFd, outEvents, outData);
	if (result != ALOOPER_POLL_CALLBACK) {
	return result;
	}

	nsecs_t timeoutNanos = endTime - systemTime(SYSTEM_TIME_MONOTONIC);
	if (timeoutNanos <= 0) {
	return ALOOPER_POLL_TIMEOUT;
	}

	timeoutMillis = int(nanoseconds_to_milliseconds(timeoutNanos + 999999LL));
	}
	}
	}

	void Looper::wake() {
	#if DEBUG_POLL_AND_WAKE
	LOGD("%p ~ wake", this);
	#endif

	ssize_t nWrite;
	do {
	nWrite = write(mWakeWritePipeFd, "W", 1);
	} while (nWrite == -1 && errno == EINTR);

	if (nWrite != 1) {
	if (errno != EAGAIN) {
	LOGW("Could not write wake signal, errno=%d", errno);
	}
	}
	}

	int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data) {
	#if DEBUG_CALLBACKS
	LOGD("%p ~ addFd - fd=%d, ident=%d, events=0x%x, callback=%p, data=%p", this, fd, ident,
	events, callback, data);
	#endif

	int epollEvents = 0;
	if (events & ALOOPER_EVENT_INPUT) epollEvents \|= EPOLLIN;
	if (events & ALOOPER_EVENT_OUTPUT) epollEvents \|= EPOLLOUT;
	if (events & ALOOPER_EVENT_ERROR) epollEvents \|= EPOLLERR;
	if (events & ALOOPER_EVENT_HANGUP) epollEvents \|= EPOLLHUP;

	if (epollEvents == 0) {
	LOGE("Invalid attempt to set a callback with no selected poll events.");
	return -1;
	}

	if (! callback) {
	if (! mAllowNonCallbacks) {
	LOGE("Invalid attempt to set NULL callback but not allowed for this looper.");
	return -1;
	}

	if (ident < 0) {
	LOGE("Invalid attempt to set NULL callback with ident <= 0.");
	return -1;
	}
	}

	{ // acquire lock
	AutoMutex _l(mLock);

	Request request;
	request.fd = fd;
	request.ident = ident;
	request.callback = callback;
	request.data = data;

	struct epoll_event eventItem;
	memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
	eventItem.events = epollEvents;
	eventItem.data.fd = fd;

	ssize_t requestIndex = mRequests.indexOfKey(fd);
	if (requestIndex < 0) {
	int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
	if (epollResult < 0) {
	LOGE("Error adding epoll events for fd %d, errno=%d", fd, errno);
	return -1;
	}
	mRequests.add(fd, request);
	} else {
	int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);
	if (epollResult < 0) {
	LOGE("Error modifying epoll events for fd %d, errno=%d", fd, errno);
	return -1;
	}
	mRequests.replaceValueAt(requestIndex, request);
	}
	} // release lock
	return 1;
	}

	int Looper::removeFd(int fd) {
	#if DEBUG_CALLBACKS
	LOGD("%p ~ removeFd - fd=%d", this, fd);
	#endif

	{ // acquire lock
	AutoMutex _l(mLock);
	ssize_t requestIndex = mRequests.indexOfKey(fd);
	if (requestIndex < 0) {
	return 0;
	}

	int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_DEL, fd, NULL);
	if (epollResult < 0) {
	LOGE("Error removing epoll events for fd %d, errno=%d", fd, errno);
	return -1;
	}

	mRequests.removeItemsAt(requestIndex);
	} // request lock
	return 1;
	}

	} // namespace android