Add async callback support

src/internal/async_callback.h

@@ -0,0 +1,59 @@
+// Copyright 2018 Slightech Co., Ltd. All rights reserved.
+//
+// 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.
+#ifndef MYNTEYE_INTERNAL_ASYNC_CALLBACK_H_  // NOLINT
+#define MYNTEYE_INTERNAL_ASYNC_CALLBACK_H_
+#pragma once
+
+#include <condition_variable>
+#include <functional>
+#include <mutex>
+#include <string>
+#include <thread>
+
+#include "mynteye/mynteye.h"
+
+MYNTEYE_BEGIN_NAMESPACE
+
+template <class Data>
+class AsyncCallback {
+ public:
+  using callback_t = std::function<void(Data data)>;
+
+  AsyncCallback(std::string name, callback_t callback);
+  ~AsyncCallback();
+
+  void PushData(Data data);
+
+ private:
+  void Run();
+
+  std::string name_;
+
+  callback_t callback_;
+
+  std::mutex mtx_;
+  std::condition_variable cv_;
+
+  bool running_;
+  std::thread thread_;
+
+  Data data_;
+  std::uint32_t count_;
+};
+
+MYNTEYE_END_NAMESPACE
+
+#include "internal/async_callback_impl.h"
+
+#endif  // MYNTEYE_INTERNAL_ASYNC_CALLBACK_H_ NOLINT

src/internal/async_callback_impl.h

@@ -0,0 +1,78 @@
+// Copyright 2018 Slightech Co., Ltd. All rights reserved.
+//
+// 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.
+#ifndef MYNTEYE_INTERNAL_ASYNC_CALLBACK_IMPL_H_  // NOLINT
+#define MYNTEYE_INTERNAL_ASYNC_CALLBACK_IMPL_H_
+#pragma once
+
+#include <glog/logging.h>
+
+#include <string>
+#include <utility>
+
+MYNTEYE_BEGIN_NAMESPACE
+
+template <class Data>
+AsyncCallback<Data>::AsyncCallback(std::string name, callback_t callback)
+    : name_(std::move(name)), callback_(std::move(callback)), count_(0) {
+  VLOG(2) << __func__;
+  running_ = true;
+  thread_ = std::thread(&AsyncCallback<Data>::Run, this);
+}
+
+template <class Data>
+AsyncCallback<Data>::~AsyncCallback() {
+  VLOG(2) << __func__;
+  {
+    std::lock_guard<std::mutex> _(mtx_);
+    running_ = false;
+    ++count_;
+  }
+  cv_.notify_one();
+  if (thread_.joinable()) {
+    thread_.join();
+  }
+}
+
+template <class Data>
+void AsyncCallback<Data>::PushData(Data data) {
+  std::lock_guard<std::mutex> _(mtx_);
+  data_ = data;
+  ++count_;
+  cv_.notify_one();
+}
+
+template <class Data>
+void AsyncCallback<Data>::Run() {
+  VLOG(2) << "AsyncCallback(" << name_ << ") thread start";
+  while (true) {
+    std::unique_lock<std::mutex> lock(mtx_);
+    cv_.wait(lock, [this] { return count_ > 0; });
+
+    if (!running_)
+      break;
+
+    if (callback_)
+      callback_(data_);
+
+    if (VLOG_IS_ON(2) && count_ > 1) {
+      VLOG(2) << "AsyncCallback(" << name_ << ") dropped " << (count_ - 1);
+    }
+    count_ = 0;
+  }
+  VLOG(2) << "AsyncCallback(" << name_ << ") thread end";
+}
+
+MYNTEYE_END_NAMESPACE
+
+#endif  // MYNTEYE_INTERNAL_ASYNC_CALLBACK_IMPL_H_ NOLINT