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//
// Copyright 2016 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.
//
#include "async_fd_watcher.h"
#include <algorithm>
#include <atomic>
#include <condition_variable>
#include <map>
#include <mutex>
#include <thread>
#include <vector>
#include "fcntl.h"
#include "sys/select.h"
#include "unistd.h"
static const int INVALID_FD = -1;
namespace android {
namespace hardware {
namespace bluetooth {
namespace async {
int AsyncFdWatcher::WatchFdForNonBlockingReads(
int file_descriptor, const ReadCallback& on_read_fd_ready_callback) {
// Add file descriptor and callback
{
std::unique_lock<std::mutex> guard(internal_mutex_);
watched_fds_[file_descriptor] = on_read_fd_ready_callback;
}
// Start the thread if not started yet
return tryStartThread();
}
int AsyncFdWatcher::ConfigureTimeout(
const std::chrono::milliseconds timeout,
const TimeoutCallback& on_timeout_callback) {
// Add timeout and callback
{
std::unique_lock<std::mutex> guard(timeout_mutex_);
timeout_cb_ = on_timeout_callback;
timeout_ms_ = timeout;
}
notifyThread();
return 0;
}
void AsyncFdWatcher::StopWatchingFileDescriptors() { stopThread(); }
AsyncFdWatcher::~AsyncFdWatcher() {}
// Make sure to call this with at least one file descriptor ready to be
// watched upon or the thread routine will return immediately
int AsyncFdWatcher::tryStartThread() {
if (std::atomic_exchange(&running_, true)) return 0;
// Set up the communication channel
int pipe_fds[2];
if (pipe2(pipe_fds, O_NONBLOCK)) return -1;
notification_listen_fd_ = pipe_fds[0];
notification_write_fd_ = pipe_fds[1];
thread_ = std::thread([this]() { ThreadRoutine(); });
if (!thread_.joinable()) return -1;
return 0;
}
int AsyncFdWatcher::stopThread() {
if (!std::atomic_exchange(&running_, false)) return 0;
notifyThread();
if (std::this_thread::get_id() != thread_.get_id()) {
thread_.join();
}
{
std::unique_lock<std::mutex> guard(internal_mutex_);
watched_fds_.clear();
}
{
std::unique_lock<std::mutex> guard(timeout_mutex_);
timeout_cb_ = nullptr;
}
return 0;
}
int AsyncFdWatcher::notifyThread() {
uint8_t buffer[] = {0};
if (TEMP_FAILURE_RETRY(write(notification_write_fd_, &buffer, 1)) < 0) {
return -1;
}
return 0;
}
void AsyncFdWatcher::ThreadRoutine() {
while (running_) {
fd_set read_fds;
FD_ZERO(&read_fds);
FD_SET(notification_listen_fd_, &read_fds);
int max_read_fd = INVALID_FD;
for (auto& it : watched_fds_) {
FD_SET(it.first, &read_fds);
max_read_fd = std::max(max_read_fd, it.first);
}
struct timeval timeout;
struct timeval* timeout_ptr = NULL;
if (timeout_ms_ > std::chrono::milliseconds(0)) {
timeout.tv_sec = timeout_ms_.count() / 1000;
timeout.tv_usec = (timeout_ms_.count() % 1000) * 1000;
timeout_ptr = &timeout;
}
// Wait until there is data available to read on some FD.
int nfds = std::max(notification_listen_fd_, max_read_fd);
int retval = select(nfds + 1, &read_fds, NULL, NULL, timeout_ptr);
// There was some error.
if (retval < 0) continue;
// Timeout.
if (retval == 0) {
// Allow the timeout callback to modify the timeout.
TimeoutCallback saved_cb;
{
std::unique_lock<std::mutex> guard(timeout_mutex_);
if (timeout_ms_ > std::chrono::milliseconds(0)) saved_cb = timeout_cb_;
}
if (saved_cb != nullptr) saved_cb();
continue;
}
// Read data from the notification FD.
if (FD_ISSET(notification_listen_fd_, &read_fds)) {
char buffer[] = {0};
TEMP_FAILURE_RETRY(read(notification_listen_fd_, buffer, 1));
continue;
}
// Invoke the data ready callbacks if appropriate.
std::vector<decltype(watched_fds_)::value_type> saved_callbacks;
{
std::unique_lock<std::mutex> guard(internal_mutex_);
for (auto& it : watched_fds_) {
if (FD_ISSET(it.first, &read_fds)) {
saved_callbacks.push_back(it);
}
}
}
for (auto& it : saved_callbacks) {
if (it.second) {
it.second(it.first);
}
}
}
}
} // namespace async
} // namespace bluetooth
} // namespace hardware
} // namespace android
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