gdata: Add GDataDirectoryService::GetEntryInfoPairByPaths()

chrome/browser/chromeos/gdata/gdata_files.h

Index: chrome/browser/chromeos/gdata/gdata_files.h
diff --git a/chrome/browser/chromeos/gdata/gdata_files.h b/chrome/browser/chromeos/gdata/gdata_files.h
index 4a5196dbf47e590f360028598340b30678859b43..2ee7117600b7a30d1c8e672fc178dee8a3dd840f 100644
--- a/chrome/browser/chromeos/gdata/gdata_files.h
+++ b/chrome/browser/chromeos/gdata/gdata_files.h
@@ -88,6 +88,26 @@ typedef base::Callback<void(GDataFileError error,
                             scoped_ptr<GDataEntryProtoVector> entries)>
     ReadDirectoryCallback;
 
+// The result of GetEntryInfoPairCallback(). Used to get a pair of entries
+// in one function call.
+struct EntryInfoPairResult {
+  EntryInfoPairResult();
+  ~EntryInfoPairResult();
+
+  FilePath first_path;

[achuithb, 2012/08/08 20:50:32]

Have you considered creating another struct like
struct EntryInfoResult {
  EntryInfoResult(const FilePath& path, GDataFileError error,
scoped_ptr<GDataEntryProto> proto);
  FilePath path; 
  GDataFileError error;
  scoped_ptr<GDataEntryProto> proto;
}

and then
struct EntryInfoPairResult {
  EntryInfoResult first;
  EntryInfoResult second;
};

I think this will make the code cleaner (especially having the ctor for
EntryInfoResult).

[satorux1, 2012/08/08 21:21:21]

Considered but I was too lazy to rewrite. :) Reconsidered and changed per your
suggestion.

+  GDataFileError first_error;
+  scoped_ptr<GDataEntryProto> first_proto;
+
+  // The following fields are filled only if the first path is found.
+  FilePath second_path;
+  GDataFileError second_error;
+  scoped_ptr<GDataEntryProto> second_proto;
+};
+
+// Used to receive the result from GetEntryInfoPairCallback().
+typedef base::Callback<void(scoped_ptr<EntryInfoPairResult> pair_result)>
+    GetEntryInfoPairCallback;
+
 // Base class for representing files and directories in gdata virtual file
 // system.
 class GDataEntry {
@@ -429,6 +449,17 @@ class GDataDirectoryService {
   void ReadDirectoryByPath(const FilePath& file_path,
                            const ReadDirectoryCallback& callback);
 
+  // Similar to GetEntryInfoByPath() but this function finds a pair of
+  // entries by |first_path| and |second_path|. If the entry for
+  // |first_path| is not found, this function does not try to get the
+  // entry of |second_path|.
+  //
+  // Must be called from UI thread. |callback| is run on UI thread.
+  void GetEntryInfoPairByPaths(
+      const FilePath& first_path,
+      const FilePath& second_path,
+      const GetEntryInfoPairCallback& callback);
+
   // Replaces file entry with the same resource id as |fresh_file| with its
   // fresh value |fresh_file|.
   void RefreshFile(scoped_ptr<GDataFile> fresh_file);
@@ -463,6 +494,22 @@ class GDataDirectoryService {
   scoped_ptr<GDataEntry> FromProtoString(
       const std::string& serialized_proto);
 
+  // ...
+  void GetEntryInfoPairByPathsAfterGetFirst(
+      const FilePath& first_path,
+      const FilePath& second_path,
+      const GetEntryInfoPairCallback& callback,
+      GDataFileError error,
+      scoped_ptr<GDataEntryProto> entry_proto);
+
+  // ...
+  void GetEntryInfoPairByPathsAfterGetSecond(
+      const FilePath& second_path,
+      const GetEntryInfoPairCallback& callback,
+      scoped_ptr<EntryInfoPairResult> result,
+      GDataFileError error,
+      scoped_ptr<GDataEntryProto> entry_proto);
+
   // Private data members.
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
   scoped_ptr<ResourceMetadataDB> directory_service_db_;