Instant: Allow empty sets to be added to the cache.

BUG=223671
R=shishir@chromium.org,brettw@chromium.org
TEST=See bug.

Review URL: https://codereview.chromium.org/12742014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@190516 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/instant_restricted_id_cache.h

@@ -68,6 +68,7 @@ class InstantRestrictedIDCache {
   FRIEND_TEST_ALL_PREFIXES(InstantRestrictedIDCacheTest, CrazyIDGeneration);
   FRIEND_TEST_ALL_PREFIXES(InstantRestrictedIDCacheTest, ManualIDGeneration);
   FRIEND_TEST_ALL_PREFIXES(InstantRestrictedIDCacheTest, MixIDGeneration);
+  FRIEND_TEST_ALL_PREFIXES(InstantRestrictedIDCacheTest, AddEmptySet);
 
   typedef base::MRUCache<InstantRestrictedID, T> CacheImpl;
 
@@ -92,8 +93,12 @@ InstantRestrictedIDCache<T>::~InstantRestrictedIDCache() {
 
 template <typename T>
 void InstantRestrictedIDCache<T>::AddItems(const ItemVector& items) {
-  if (items.size() == 0 || items.size() > cache_.max_size())
+  DCHECK_LE(items.size(), cache_.max_size());
+
+  if (items.empty()) {
+    last_add_start_ = cache_.rend();
     return;
+  }
 
   for (size_t i = 0; i < items.size(); ++i) {
     InstantRestrictedID id = ++last_restricted_id_;
@@ -106,8 +111,12 @@ void InstantRestrictedIDCache<T>::AddItems(const ItemVector& items) {
 template <typename T>
 void InstantRestrictedIDCache<T>::AddItemsWithRestrictedID(
     const ItemIDVector& items) {
-  if (items.size() == 0 || items.size() > cache_.max_size())
+  DCHECK_LE(items.size(), cache_.max_size());
+
+  if (items.empty()) {
+    last_add_start_ = cache_.rend();
     return;
+  }
 
   std::set<InstantRestrictedID> ids_added;
   for (size_t i = 0; i < items.size(); ++i) {

chrome/common/instant_restricted_id_cache_unittest.cc

@@ -346,3 +346,49 @@ TEST_F(InstantRestrictedIDCacheTest, MixIDGeneration) {
   EXPECT_TRUE(cache.GetItemWithRestrictedID(7, &t));
   EXPECT_EQ(input3[2].second, t);
 }
+
+TEST_F(InstantRestrictedIDCacheTest, AddEmptySet) {
+  InstantRestrictedIDCache<TestData> cache(9);
+  EXPECT_EQ(0u, cache.cache_.size());
+  EXPECT_EQ(0, cache.last_restricted_id_);
+
+  // Add a non-empty set of items.
+  std::vector<TestData> input1;
+  input1.push_back(TestData("A"));
+  input1.push_back(TestData("B"));
+  input1.push_back(TestData("C"));
+  cache.AddItems(input1);
+  EXPECT_EQ(3u, cache.cache_.size());
+  EXPECT_EQ(3, cache.last_restricted_id_);
+
+  std::vector<ItemIDPair> output;
+  cache.GetCurrentItems(&output);
+  EXPECT_EQ(3u, output.size());
+
+  // Add an empty set.
+  cache.AddItems(std::vector<TestData>());
+  EXPECT_EQ(3u, cache.cache_.size());
+  EXPECT_EQ(3, cache.last_restricted_id_);
+
+  cache.GetCurrentItems(&output);
+  EXPECT_TRUE(output.empty());
+
+  // Manual IDs.
+  std::vector<ItemIDPair> input2;
+  input2.push_back(std::make_pair(10, TestData("A")));
+  input2.push_back(std::make_pair(11, TestData("B")));
+  input2.push_back(std::make_pair(12, TestData("C")));
+  cache.AddItemsWithRestrictedID(input2);
+  EXPECT_EQ(6u, cache.cache_.size());
+  EXPECT_EQ(12, cache.last_restricted_id_);
+
+  cache.GetCurrentItems(&output);
+  EXPECT_EQ(3u, output.size());
+
+  cache.AddItemsWithRestrictedID(std::vector<ItemIDPair>());
+  EXPECT_EQ(6u, cache.cache_.size());
+  EXPECT_EQ(12, cache.last_restricted_id_);
+
+  cache.GetCurrentItems(&output);
+  EXPECT_TRUE(output.empty());
+}