Keep track of which attachments are referenced by which sync entries.

sync/syncable/directory.h

 // Copyright 2013 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 SYNC_SYNCABLE_DIRECTORY_H_
 #define SYNC_SYNCABLE_DIRECTORY_H_
 
 #include <deque>
 #include <set>
 #include <string>
@@ skipping 29 matching lines @@
 class ScopedKernelLock;
 class TransactionObserver;
 class WriteTransaction;
 
 enum InvariantCheckLevel {
   OFF = 0,            // No checking.
   VERIFY_CHANGES = 1, // Checks only mutated entries.  Does not check hierarchy.
   FULL_DB_VERIFICATION = 2 // Check every entry.  This can be expensive.
 };
 
+// Directory stores and manages EntryKernels.
+//
+// This class is tightly coupled to several other classes (see friends).
 class SYNC_EXPORT Directory {
   friend class BaseTransaction;
   friend class Entry;
   friend class ModelNeutralMutableEntry;
   friend class MutableEntry;
   friend class ReadTransaction;
   friend class ScopedKernelLock;
   friend class WriteTransaction;
   friend class SyncableDirectoryTest;
   friend class syncer::TestUserShare;
@@ skipping 13 matching lines @@
   //
   // It gets worse, though.  The Anroid STL library has a bug that means it may
   // invalidate all iterators when you erase from the map, too.  That means that
   // you can't iterate while erasing.  STLDeleteElements(), std::remove_if(),
   // and other similar functions are off-limits too, until this bug is fixed.
   //
   // See http://sourceforge.net/p/stlport/bugs/239/.
   typedef base::hash_map<int64, EntryKernel*> MetahandlesMap;
   typedef base::hash_map<std::string, EntryKernel*> IdsMap;
   typedef base::hash_map<std::string, EntryKernel*> TagsMap;
+  typedef std::string AttachmentIdUniqueId;
+  typedef base::hash_map<AttachmentIdUniqueId, MetahandleSet>
+      IndexByAttachmentId;
 
   static const base::FilePath::CharType kSyncDatabaseFilename[];
 
   // The dirty/clean state of kernel fields backed by the share_info table.
   // This is public so it can be used in SaveChangesSnapshot for persistence.
   enum KernelShareInfoStatus {
     KERNEL_SHARE_INFO_INVALID,
     KERNEL_SHARE_INFO_VALID,
     KERNEL_SHARE_INFO_DIRTY
   };
@@ skipping 283 matching lines @@
   // Returns: true on success, false if an error was encountered.
   virtual bool PurgeEntriesWithTypeIn(ModelTypeSet disabled_types,
                                       ModelTypeSet types_to_journal,
                                       ModelTypeSet types_to_unapply);
 
   // Resets the base_versions and server_versions of all synced entities
   // associated with |type| to 1.
   // WARNING! This can be slow, as it iterates over all entries for a type.
   bool ResetVersionsForType(BaseWriteTransaction* trans, ModelType type);
 
+  // Returns true iff the attachment identified by |attachment_id_proto| is
+  // linked to an entry.
+  //
+  // An attachment linked to a deleted entry is still considered linked if the
+  // entry hasn't yet been purged.
+  bool IsAttachmentLinked(
+      const sync_pb::AttachmentIdProto& attachment_id_proto) const;
+
  protected:  // for friends, mainly used by Entry constructors
   virtual EntryKernel* GetEntryByHandle(int64 handle);
   virtual EntryKernel* GetEntryByHandle(int64 metahandle,
       ScopedKernelLock* lock);
   virtual EntryKernel* GetEntryById(const Id& id);
   EntryKernel* GetEntryByServerTag(const std::string& tag);
   virtual EntryKernel* GetEntryByClientTag(const std::string& tag);
   bool ReindexId(BaseWriteTransaction* trans, EntryKernel* const entry,
                  const Id& new_id);
   bool ReindexParentId(BaseWriteTransaction* trans, EntryKernel* const entry,
                        const Id& new_parent_id);
+  // Update the attachment index for |metahandle| removing it from the index
+  // under |old_metadata| entries and add it under |new_metadata| entries.
+  void UpdateAttachmentIndex(const int64 metahandle,
+                             const sync_pb::AttachmentMetadata& old_metadata,
+                             const sync_pb::AttachmentMetadata& new_metadata);
   void ClearDirtyMetahandles();
 
   DirOpenResult OpenImpl(
       const std::string& name,
       DirectoryChangeDelegate* delegate,
       const WeakHandle<TransactionObserver>& transaction_observer);
 
  private:
   struct Kernel {
     // |delegate| must not be NULL.  |transaction_observer| must be
@@ skipping 37 matching lines @@
 
     // Entries indexed by client tag.
     // This map does not include any entries with non-existent client tags.
     // IS_DEL items are included.
     TagsMap client_tags_map;
 
     // Contains non-deleted items, indexed according to parent and position
     // within parent.  Protected by the ScopedKernelLock.
     ParentChildIndex parent_child_index;
 
+    // This index keeps track of which metahandles refer to a given attachment.
+    // Think of it as the inverse of EntryKernel's AttachmentMetadata Records.
+    //
+    // Because entries can be undeleted (e.g. PutIsDel(false)), entries should
+    // not removed from the index until they are actually deleted from memory.
+    //
+    // All access should go through IsAttachmentLinked,
+    // RemoveFromAttachmentIndex, AddToAttachmentIndex, and
+    // UpdateAttachmentIndex methods to avoid iterator invalidation errors.
+    IndexByAttachmentId index_by_attachment_id;
+
     // 3 in-memory indices on bits used extremely frequently by the syncer.
     // |unapplied_update_metahandles| is keyed by the server model type.
     MetahandleSet unapplied_update_metahandles[MODEL_TYPE_COUNT];
     MetahandleSet unsynced_metahandles;
     // Contains metahandles that are most likely dirty (though not
     // necessarily).  Dirtyness is confirmed in TakeSnapshotForSaveChanges().
     MetahandleSet dirty_metahandles;
 
     // When a purge takes place, we remove items from all our indices and stash
     // them in here so that SaveChanges can persist their permanent deletion.
@@ skipping 72 matching lines @@
 
   // Append the handles of the children of |parent_id| to |result|.
   void AppendChildHandles(
       const ScopedKernelLock& lock,
       const Id& parent_id, Directory::Metahandles* result);
 
   // Helper methods used by PurgeDisabledTypes.
   void UnapplyEntry(EntryKernel* entry);
   void DeleteEntry(bool save_to_journal,
                    EntryKernel* entry,
-                   EntryKernelSet* entries_to_journal);
+                   EntryKernelSet* entries_to_journal,
+                   const ScopedKernelLock& lock);
+
+  // Remove each of |metahandle|'s attachment ids from index_by_attachment_id.
+  void RemoveFromAttachmentIndex(
+      const int64 metahandle,
+      const sync_pb::AttachmentMetadata& attachment_metadata,
+      const ScopedKernelLock& lock);
+  // Add each of |metahandle|'s attachment ids to the index_by_attachment_id.
+  void AddToAttachmentIndex(
+      const int64 metahandle,
+      const sync_pb::AttachmentMetadata& attachment_metadata,
+      const ScopedKernelLock& lock);
 
   Kernel* kernel_;
 
   scoped_ptr<DirectoryBackingStore> store_;
 
   UnrecoverableErrorHandler* const unrecoverable_error_handler_;
   const ReportUnrecoverableErrorFunction report_unrecoverable_error_function_;
   bool unrecoverable_error_set_;
 
   // Not owned.
   NigoriHandler* const nigori_handler_;
   Cryptographer* const cryptographer_;
 
   InvariantCheckLevel invariant_check_level_;
 
   // Maintain deleted entries not in |kernel_| until it's verified that they
   // are deleted in native models as well.
   scoped_ptr<DeleteJournal> delete_journal_;
 
   DISALLOW_COPY_AND_ASSIGN(Directory);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif // SYNC_SYNCABLE_DIRECTORY_H_