Prefetch cache pt1 - MRU

chrome/browser/autocomplete/answers_cache.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_AUTOCOMPLETE_ANSWERS_CACHE_H_
+#define CHROME_BROWSER_AUTOCOMPLETE_ANSWERS_CACHE_H_
+
+#include <list>
+
+#include "base/basictypes.h"
+#include "base/strings/string16.h"
+
+struct AnswersQueryData {
+  AnswersQueryData();
+  AnswersQueryData(const base::string16& full_query_text,
+                   const base::string16& query_type);
+  base::string16 full_query_text;
+  base::string16 query_type;
+};
+
+// Cache for the most-recently seen answer for Answers in Suggest.
+class AnswersCache {
+ public:
+  explicit AnswersCache(size_t max_entries);
+  ~AnswersCache();
+
+  // Gets the top answer query completion for the query term. The query data
+  // will contain empty query text and type if no matching data was found.
+  AnswersQueryData GetTopAnswerEntry(const base::string16& query);
+
+  // Registers a query that received an answer suggestion.
+  void UpdateRecentAnswers(const base::string16& full_query_text,
+                           const base::string16& query_type);
+
+  // Signals if cache is empty.
+  bool empty() const { return cache_.empty(); }
+
+ private:
+  size_t max_entries_;
+  typedef std::list<AnswersQueryData> Cache;
+  Cache cache_;
+
+  DISALLOW_COPY_AND_ASSIGN(AnswersCache);
+};
+
+#endif  // CHROME_BROWSER_AUTOCOMPLETE_ANSWERS_CACHE_H_