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/*
* Copyright (C) 2007 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.
*/
#define LOG_TAG "selector"
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <cutils/array.h>
#include <cutils/selector.h>
#include "loghack.h"
struct Selector {
Array* selectableFds;
bool looping;
fd_set readFds;
fd_set writeFds;
fd_set exceptFds;
int maxFd;
int wakeupPipe[2];
SelectableFd* wakeupFd;
bool inSelect;
pthread_mutex_t inSelectLock;
};
/** Reads and ignores wake up data. */
static void eatWakeupData(SelectableFd* wakeupFd) {
static char garbage[64];
if (read(wakeupFd->fd, garbage, sizeof(garbage)) < 0) {
if (errno == EINTR) {
ALOGI("read() interrupted.");
} else {
LOG_ALWAYS_FATAL("This should never happen: %s", strerror(errno));
}
}
}
static void setInSelect(Selector* selector, bool inSelect) {
pthread_mutex_lock(&selector->inSelectLock);
selector->inSelect = inSelect;
pthread_mutex_unlock(&selector->inSelectLock);
}
static bool isInSelect(Selector* selector) {
pthread_mutex_lock(&selector->inSelectLock);
bool inSelect = selector->inSelect;
pthread_mutex_unlock(&selector->inSelectLock);
return inSelect;
}
void selectorWakeUp(Selector* selector) {
if (!isInSelect(selector)) {
// We only need to write wake-up data if we're blocked in select().
return;
}
static char garbage[1];
if (write(selector->wakeupPipe[1], garbage, sizeof(garbage)) < 0) {
if (errno == EINTR) {
ALOGI("read() interrupted.");
} else {
LOG_ALWAYS_FATAL("This should never happen: %s", strerror(errno));
}
}
}
Selector* selectorCreate(void) {
Selector* selector = calloc(1, sizeof(Selector));
if (selector == NULL) {
LOG_ALWAYS_FATAL("malloc() error.");
}
selector->selectableFds = arrayCreate();
// Set up wake-up pipe.
if (pipe(selector->wakeupPipe) < 0) {
LOG_ALWAYS_FATAL("pipe() error: %s", strerror(errno));
}
ALOGD("Wakeup fd: %d", selector->wakeupPipe[0]);
SelectableFd* wakeupFd = selectorAdd(selector, selector->wakeupPipe[0]);
if (wakeupFd == NULL) {
LOG_ALWAYS_FATAL("malloc() error.");
}
wakeupFd->onReadable = &eatWakeupData;
pthread_mutex_init(&selector->inSelectLock, NULL);
return selector;
}
SelectableFd* selectorAdd(Selector* selector, int fd) {
assert(selector != NULL);
SelectableFd* selectableFd = calloc(1, sizeof(SelectableFd));
if (selectableFd != NULL) {
selectableFd->selector = selector;
selectableFd->fd = fd;
arrayAdd(selector->selectableFds, selectableFd);
}
return selectableFd;
}
/**
* Adds an fd to the given set if the callback is non-null. Returns true
* if the fd was added.
*/
static inline bool maybeAdd(SelectableFd* selectableFd,
void (*callback)(SelectableFd*), fd_set* fdSet) {
if (callback != NULL) {
FD_SET(selectableFd->fd, fdSet);
return true;
}
return false;
}
/**
* Removes stale file descriptors and initializes file descriptor sets.
*/
static void prepareForSelect(Selector* selector) {
fd_set* exceptFds = &selector->exceptFds;
fd_set* readFds = &selector->readFds;
fd_set* writeFds = &selector->writeFds;
FD_ZERO(exceptFds);
FD_ZERO(readFds);
FD_ZERO(writeFds);
Array* selectableFds = selector->selectableFds;
int i = 0;
selector->maxFd = 0;
int size = arraySize(selectableFds);
while (i < size) {
SelectableFd* selectableFd = arrayGet(selectableFds, i);
if (selectableFd->remove) {
// This descriptor should be removed.
arrayRemove(selectableFds, i);
size--;
if (selectableFd->onRemove != NULL) {
selectableFd->onRemove(selectableFd);
}
free(selectableFd);
} else {
if (selectableFd->beforeSelect != NULL) {
selectableFd->beforeSelect(selectableFd);
}
bool inSet = false;
if (maybeAdd(selectableFd, selectableFd->onExcept, exceptFds)) {
ALOGD("Selecting fd %d for writing...", selectableFd->fd);
inSet = true;
}
if (maybeAdd(selectableFd, selectableFd->onReadable, readFds)) {
ALOGD("Selecting fd %d for reading...", selectableFd->fd);
inSet = true;
}
if (maybeAdd(selectableFd, selectableFd->onWritable, writeFds)) {
inSet = true;
}
if (inSet) {
// If the fd is in a set, check it against max.
int fd = selectableFd->fd;
if (fd > selector->maxFd) {
selector->maxFd = fd;
}
}
// Move to next descriptor.
i++;
}
}
}
/**
* Invokes a callback if the callback is non-null and the fd is in the given
* set.
*/
static inline void maybeInvoke(SelectableFd* selectableFd,
void (*callback)(SelectableFd*), fd_set* fdSet) {
if (callback != NULL && !selectableFd->remove &&
FD_ISSET(selectableFd->fd, fdSet)) {
ALOGD("Selected fd %d.", selectableFd->fd);
callback(selectableFd);
}
}
/**
* Notifies user if file descriptors are readable or writable, or if
* out-of-band data is present.
*/
static void fireEvents(Selector* selector) {
Array* selectableFds = selector->selectableFds;
int size = arraySize(selectableFds);
int i;
for (i = 0; i < size; i++) {
SelectableFd* selectableFd = arrayGet(selectableFds, i);
maybeInvoke(selectableFd, selectableFd->onExcept,
&selector->exceptFds);
maybeInvoke(selectableFd, selectableFd->onReadable,
&selector->readFds);
maybeInvoke(selectableFd, selectableFd->onWritable,
&selector->writeFds);
}
}
void selectorLoop(Selector* selector) {
// Make sure we're not already looping.
if (selector->looping) {
LOG_ALWAYS_FATAL("Already looping.");
}
selector->looping = true;
while (true) {
setInSelect(selector, true);
prepareForSelect(selector);
ALOGD("Entering select().");
// Select file descriptors.
int result = select(selector->maxFd + 1, &selector->readFds,
&selector->writeFds, &selector->exceptFds, NULL);
ALOGD("Exiting select().");
setInSelect(selector, false);
if (result == -1) {
// Abort on everything except EINTR.
if (errno == EINTR) {
ALOGI("select() interrupted.");
} else {
LOG_ALWAYS_FATAL("select() error: %s",
strerror(errno));
}
} else if (result > 0) {
fireEvents(selector);
}
}
}
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