PVer4: Drop hash prefixes based on the removals field in the response

components/safe_browsing_db/v4_store.h

 // Copyright 2016 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 COMPONENTS_SAFE_BROWSING_DB_V4_STORE_H_
 #define COMPONENTS_SAFE_BROWSING_DB_V4_STORE_H_
 
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 110 matching lines @@
   // The number of bytes in additions isn't a multiple of prefix size.
   ADDITIONS_SIZE_UNEXPECTED_FAILURE = 4,
 
   // The update received from the server contains a prefix that's already
   // present in the map.
   ADDITIONS_HAS_EXISTING_PREFIX_FAILURE = 5,
 
   // The server sent a response_type that the client did not expect.
   UNEXPECTED_RESPONSE_TYPE_FAILURE = 6,
 
+  // One of more index(es) in removals field of the response is greater than
+  // the number of hash prefixes currently in the (old) store.
+  REMOVALS_INDEX_TOO_LARGE = 7,
+
   // Memory space for histograms is determined by the max.  ALWAYS
   // ADD NEW VALUES BEFORE THIS ONE.
   APPLY_UPDATE_RESULT_MAX
 };
 
 // Factory for creating V4Store. Tests implement this factory to create fake
 // stores for testing.
 class V4StoreFactory {
  public:
   virtual ~V4StoreFactory() {}
@@ skipping 49 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestGetNextSmallestUnmergedPrefix);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesWithSameSizesInEachMap);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
                            TestMergeUpdatesWithDifferentSizesInEachMap);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesOldMapRunsOutFirst);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
                            TestMergeUpdatesAdditionsMapRunsOutFirst);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
                            TestMergeUpdatesFailsForRepeatedHashPrefix);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
+                           TestMergeUpdatesFailsWhenRemovalsIndexTooLarge);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesRemovesOnlyElement);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesRemovesFirstElement);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesRemovesMiddleElement);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest, TestMergeUpdatesRemovesLastElement);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
+                           TestMergeUpdatesRemovesWhenOldHasDifferentSizes);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
+                           TestMergeUpdatesRemovesMultipleAcrossDifferentSizes);
+  FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
                            TestReadFullResponseWithValidHashPrefixMap);
   FRIEND_TEST_ALL_PREFIXES(V4StoreTest,
                            TestReadFullResponseWithInvalidHashPrefixMap);
 
   // If |prefix_size| is within expected range, and |raw_hashes| is not invalid,
   // then it sets |raw_hashes| as the value at key |prefix_size| in
   // |additions_map|
   static ApplyUpdateResult AddUnlumpedHashes(PrefixSize prefix_size,
                                              const std::string& raw_hashes,
                                              HashPrefixMap* additions_map);
@@ skipping 21 matching lines @@
                                       HashPrefixMap* prefix_map_to_update);
 
   // Updates the |additions_map| with the additions received in the partial
   // update from the server.
   static ApplyUpdateResult UpdateHashPrefixMapFromAdditions(
       const ::google::protobuf::RepeatedPtrField<ThreatEntrySet>& additions,
       HashPrefixMap* additions_map);
 
   // Merges the prefix map from the old store (|old_hash_prefix_map|) and the
   // update (additions_map) to populate the prefix map for the current store.
-  // TODO(vakh): Process removals also.
+  // The indices in the |raw_removals| list, which may be NULL, are not merged.
   ApplyUpdateResult MergeUpdate(const HashPrefixMap& old_hash_prefix_map,
-                                const HashPrefixMap& additions_map);
+                                const HashPrefixMap& additions_map,
+                                const ::google::protobuf::RepeatedField<
+                                    ::google::protobuf::int32>* raw_removals);
 
   // Reads the state of the store from the file on disk and returns the reason
   // for the failure or reports success.
   StoreReadResult ReadFromDisk();
 
   // Writes the FULL_UPDATE |response| to disk as a V4StoreFileFormat proto.
   StoreWriteResult WriteToDisk(
       std::unique_ptr<ListUpdateResponse> response) const;
 
   // The state of the store as returned by the PVer4 server in the last applied
   // update response.
   std::string state_;
   const base::FilePath store_path_;
   HashPrefixMap hash_prefix_map_;
   const scoped_refptr<base::SequencedTaskRunner> task_runner_;
 };
 
 std::ostream& operator<<(std::ostream& os, const V4Store& store);
 
 }  // namespace safe_browsing
 
 #endif  // COMPONENTS_SAFE_BROWSING_DB_V4_STORE_H_