Add default Bluetooth HAL implementation

Also added initial target-side functional test.

Test: bluetooth_hidl_hal_test
Bug: 31972505
Change-Id: I1f574a5b2b53d7fbf65dbb4e1aaa5f8b6c5a9448
diff --git a/bluetooth/1.0/default/async_fd_watcher.cc b/bluetooth/1.0/default/async_fd_watcher.cc
new file mode 100644
index 0000000..636b4b6
--- /dev/null
+++ b/bluetooth/1.0/default/async_fd_watcher.cc
@@ -0,0 +1,133 @@
+//
+// 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 <mutex>
+#include <thread>
+#include <vector>
+#include "fcntl.h"
+#include "sys/select.h"
+#include "unistd.h"
+
+namespace android {
+namespace hardware {
+namespace bluetooth {
+namespace V1_0 {
+namespace implementation {
+
+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_);
+    read_fd_ = file_descriptor;
+    cb_ = on_read_fd_ready_callback;
+  }
+
+  // Start the thread if not started yet
+  int started = tryStartThread();
+  if (started != 0) {
+    return started;
+  }
+
+  return 0;
+}
+
+void AsyncFdWatcher::StopWatchingFileDescriptor() { 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_);
+    cb_ = nullptr;
+    read_fd_ = -1;
+  }
+
+  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);
+    FD_SET(read_fd_, &read_fds);
+
+    // Wait until there is data available to read on some FD
+    int nfds = std::max(notification_listen_fd_, read_fd_);
+    int retval = select(nfds + 1, &read_fds, NULL, NULL, NULL);
+    if (retval <= 0) continue;  // there was some error or a timeout
+
+    // 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));
+    }
+
+    // Make sure we're still running
+    if (!running_) break;
+
+    // Invoke the data ready callback if appropriate
+    if (FD_ISSET(read_fd_, &read_fds)) {
+      std::unique_lock<std::mutex> guard(internal_mutex_);
+      if (cb_) cb_(read_fd_);
+    }
+  }
+}
+
+} // namespace implementation
+} // namespace V1_0
+} // namespace bluetooth
+} // namespace hardware
+} // namespace android