IDBObserver: Lifetime Management: Adding Observer

content/browser/indexed_db/indexed_db_dispatcher_host.h

Index: content/browser/indexed_db/indexed_db_dispatcher_host.h
diff --git a/content/browser/indexed_db/indexed_db_dispatcher_host.h b/content/browser/indexed_db/indexed_db_dispatcher_host.h
index ba7a65fe36a28ac86dabe84b51889b2aa7d1e551..1af72764864a70db99237fbe1673f1c74ebd09ee 100644
--- a/content/browser/indexed_db/indexed_db_dispatcher_host.h
+++ b/content/browser/indexed_db/indexed_db_dispatcher_host.h
@@ -30,6 +30,7 @@ struct IndexedDBHostMsg_DatabaseCreateIndex_Params;
 struct IndexedDBHostMsg_DatabaseCreateObjectStore_Params;
 struct IndexedDBHostMsg_DatabaseCreateTransaction_Params;
 struct IndexedDBHostMsg_DatabaseDeleteRange_Params;
+struct IndexedDBHostMsg_DatabaseObserve_Params;
 struct IndexedDBHostMsg_DatabaseGet_Params;
 struct IndexedDBHostMsg_DatabaseGetAll_Params;
 struct IndexedDBHostMsg_DatabaseOpenCursor_Params;
@@ -108,6 +109,12 @@ class IndexedDBDispatcherHost : public BrowserMessageFilter {
       int64_t host_transaction_id);
   static uint32_t TransactionIdToProcessId(int64_t host_transaction_id);
 
+  // These are called to map a 32-bit front-end (renderer-specific) observer
+  // id to and from a back-end ("host") observer id that encodes the process
+  // id in the high 32 bits. The mapping is host-specific and ids are validated.
+  int64_t HostObserverId(int64_t observer_id);

[dmurph, 2016/06/15 12:49:43]

Why do we need these? Can we just store the ipc_thread_id and observe_id in the
observer?

It looks like you're trying to combine the ids for a map? Let's do something
like 

int64_t GenerateObserveId(int64_t ipc_thread_id, int64_t observe_id) {
  // Basic djb2 hash.
  int64_t hash = 5381;
  hash = ((hash << 5) + hash) + ipc_thread_id;
  hash = ((hash << 5) + hash) + observe_id;
  return hash;
}

[palakj1, 2016/06/16 07:05:40]

I see your point. Keeping connection_id and observer_id separate would help in
cleaning up when connection is closed or unobserve is called.
But why doesn't a simple concatenation (ipc_thread_id <<32 + observer_id) work?

[dmurph, 2016/06/16 07:30:33]

Ah, so the thread id is always int32_t, huh. Sure, that would work just fine.
just make sure you cast it to a uint64_t before you bit shift.

+  int64_t RendererObserverId(int64_t host_observer_id);
+
   std::string HoldBlobData(const IndexedDBBlobInfo& blob_info);
 
  private:
@@ -174,6 +181,7 @@ class IndexedDBDispatcherHost : public BrowserMessageFilter {
     void OnVersionChangeIgnored(int32_t ipc_database_id);
     void OnDestroyed(int32_t ipc_database_id);
 
+    void OnObserve(const IndexedDBHostMsg_DatabaseObserve_Params& params);
     void OnGet(const IndexedDBHostMsg_DatabaseGet_Params& params);
     void OnGetAll(const IndexedDBHostMsg_DatabaseGetAll_Params& params);
     // OnPutWrapper starts on the IO thread so that it can grab BlobDataHandles
@@ -217,6 +225,7 @@ class IndexedDBDispatcherHost : public BrowserMessageFilter {
     TransactionIDToSizeMap transaction_size_map_;
     TransactionIDToOriginMap transaction_origin_map_;
     TransactionIDToDatabaseIDMap transaction_database_map_;
+    std::vector<int64_t> observers_;
 
     // Weak pointers are used when an asynchronous quota request is made, in
     // case the dispatcher is torn down before the response returns.
@@ -299,7 +308,6 @@ class IndexedDBDispatcherHost : public BrowserMessageFilter {
   // Only access on IndexedDB thread.
   std::unique_ptr<DatabaseDispatcherHost> database_dispatcher_host_;
   std::unique_ptr<CursorDispatcherHost> cursor_dispatcher_host_;
-
   // Used to set file permissions for blob storage.
   int ipc_process_id_;