added missing indexed_queue (#332)

modules/planning/common/indexed_queue.h

+/******************************************************************************
+ * Copyright 2017 The Apollo Authors. 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.
+ *****************************************************************************/
+
+/**
+ * @file:
+ **/
+
+#ifndef MODULES_PLANNING_COMMON_INDEXED_QUEUE_H_
+#define MODULES_PLANNING_COMMON_INDEXED_QUEUE_H_
+
+#include <memory>
+#include <queue>
+#include <unordered_map>
+
+namespace apollo {
+namespace planning {
+
+template <typename I, typename T>
+class IndexedQueue {
+ public:
+  IndexedQueue(std::size_t max_queue_size) : max_queue_size_(max_queue_size){};
+  T *Find(const I id) const {
+    auto iter = map_.find(id);
+    if (iter == map_.end()) {
+      return nullptr;
+    } else {
+      return iter->second.get();
+    }
+  }
+
+  const T *Latest() const {
+    if (queue_.empty()) {
+      return nullptr;
+    }
+    return Find(queue_.back().first);
+  }
+
+  bool Add(const I id, std::unique_ptr<T> ptr) {
+    if (Find(id)) {
+      return false;
+    }
+    if (!queue_.empty() && queue_.size() == max_queue_size_) {
+      const auto &front = queue_.top();
+      map_.erase(front.first);
+      queue_.pop_front();
+    }
+    queue_.push_back(std::make_pair<I, ptr>(id, ptr.get()));
+    map_[id] = std::move(ptr);
+    return true;
+  }
+
+ public:
+  std::size_t max_queue_size_ = 0;
+  std::queue<std::pair<I, const T *>> queue_;
+  std::unordered_map<I, std::unique_ptr<T>> map_;
+};
+
+}  // namespace planning
+}  // namespace apollo
+
+#endif  // MODULES_PLANNING_COMMON_DATA_CENTER_H_