Prefetch cache pt1 - MRU

chrome/browser/autocomplete/answers_cache.cc

+// 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.
+
+#include "chrome/browser/autocomplete/answers_cache.h"
+
+#include "base/strings/string_util.h"
+
+AnswersQueryData::AnswersQueryData() {
+}
+AnswersQueryData::AnswersQueryData(const base::string16& text,
+                                   const base::string16& type)
+    : full_query_text(text), query_type(type) {
+}
+
+AnswersCache::AnswersCache(size_t max_entries) : max_entries_(max_entries) {
+}
+
+AnswersCache::~AnswersCache() {
+}
+
+AnswersQueryData AnswersCache::GetTopAnswerEntry(const base::string16& query) {
+  base::string16 collapsed_query = base::CollapseWhitespace(query, false);
+  for (Cache::iterator it = cache_.begin(); it != cache_.end(); ++it) {
+    // If the query text starts with trimmed input, this is valid prefetch data.
+    if (StartsWith(it->full_query_text, collapsed_query, false)) {
+      // Move the touched item to the front of the list.
+      cache_.splice(cache_.begin(), cache_, it);
+      return cache_.front();
+    }
+  }
+  return AnswersQueryData();
+}
+
+void AnswersCache::UpdateRecentAnswers(const base::string16& full_query_text,
+                                       const base::string16& query_type) {
+  // If this entry is already part of the cache, just update recency.
+  for (Cache::iterator it = cache_.begin(); it != cache_.end(); ++it) {
+    if (full_query_text == it->full_query_text &&
+        query_type == it->query_type) {
+      cache_.splice(cache_.begin(), cache_, it);
+      return;
+    }
+  }
+
+  // Evict if cache size is exceeded.
+  if (cache_.size() >= max_entries_)
+    cache_.pop_back();
+
+  cache_.emplace_front(full_query_text, query_type);
+}