V4LDM: Add check for HashPrefix match and some tests

components/safe_browsing_db/v4_local_database_manager.cc

Index: components/safe_browsing_db/v4_local_database_manager.cc
diff --git a/components/safe_browsing_db/v4_local_database_manager.cc b/components/safe_browsing_db/v4_local_database_manager.cc
index 5f555cfdd7333dc436696c4ac30767de7c779eb8..9bc2d6c3e67ea7fda44cdd84fae652ad3c3ffbfd 100644
--- a/components/safe_browsing_db/v4_local_database_manager.cc
+++ b/components/safe_browsing_db/v4_local_database_manager.cc
@@ -42,8 +42,8 @@ bool V4LocalDatabaseManager::IsSupported() const {
   return true;
 }
 
-safe_browsing::ThreatSource V4LocalDatabaseManager::GetThreatSource() const {
-  return safe_browsing::ThreatSource::LOCAL_PVER4;
+ThreatSource V4LocalDatabaseManager::GetThreatSource() const {
+  return ThreatSource::LOCAL_PVER4;
 }
 
 bool V4LocalDatabaseManager::ChecksAreAlwaysAsync() const {
@@ -140,6 +140,30 @@ bool V4LocalDatabaseManager::CheckBrowseUrl(const GURL& url, Client* client) {
     return true;
   }
 
+  // TODO(vakh): Queue check if v4_database_ isn't ready yet.
+  if (v4_database_) {
+    base::hash_set<FullHash> full_hashes;
+    V4ProtocolManagerUtil::UrlToFullHashes(url, &full_hashes);
+
+    base::hash_set<HashPrefix> matched_hash_prefixes;
+    base::hash_set<UpdateListIdentifier> matched_stores;
+    base::hash_set<UpdateListIdentifier> stores_to_look(
+        {GetUrlMalwareId(), GetUrlSocEngId()});
+    MatchedHashPrefixMap matched_hash_prefix_map;
+    for (const auto& full_hash : full_hashes) {
+      v4_database_->GetStoresMatchingFullHash(full_hash, stores_to_look,
+                                              &matched_hash_prefix_map);
+      for (const auto& matched_pair : matched_hash_prefix_map) {
+        matched_stores.insert(matched_pair.first);
+        matched_hash_prefixes.insert(matched_pair.second);
+      }
+    }
+
+    DCHECK((matched_stores.empty() && matched_hash_prefixes.empty()) ||

[Nathan Parker, 2016/08/15 19:06:41]

DECHECK_EQ(matched_stores.empty(), matched_hash_prefixes.empty())

[vakh (use Gerrit instead), 2016/08/17 18:23:06]

Done.

+           (!matched_stores.empty() && !matched_hash_prefixes.empty()));
+    // TODO(vakh): Fetch full hashes for the matching hash prefixes.

[Nathan Parker, 2016/08/15 19:06:41]

You need to invoke the client's callback asynchronously if returning false. 
Maybe it's better to just return true until then.

I'm not sure the value of splitting matched_mash_prefix_map into two hash_sets. 
It'd be better to add those once you've got a use for them, like when fetching
full hashes or invoking the client->callback (does it need them?).

[vakh (use Gerrit instead), 2016/08/17 18:23:06]

This method is not being called from product code so the return value is only
useful in unit tests right now. That's why I have implemented it so and added a
TODO.
That's what the replacement for TODO would do. This is a step in that direction.
The set is needed to get unique values for matching hash prefixes and
stores/lists.

+    return matched_hash_prefixes.empty();
+  }
   // Don't defer the resource load.
   return true;
 }