drive: Stop using callback for ResourceMetadataStorage::Iterate

chrome/browser/chromeos/drive/resource_metadata_storage.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 CHROME_BROWSER_CHROMEOS_DRIVE_RESOURCE_METADATA_STORAGE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_RESOURCE_METADATA_STORAGE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
+#include "chrome/browser/chromeos/drive/drive.pb.h"
 
 namespace leveldb {
 class DB;
+class Iterator;
 }
 
 namespace drive {
 
 class ResourceEntry;
 class ResourceMetadataHeader;
 
-typedef base::Callback<void(const ResourceEntry& entry)> IterateCallback;
-
 // Storage for ResourceMetadata which is responsible to manage entry info
 // and child-parent relationships between entries.
 class ResourceMetadataStorage {
  public:
   // This should be incremented when incompatibility change is made to DB
   // format.
   static const int kDBVersion = 5;
 
+  class Iterator {
+   public:
+    explicit Iterator(scoped_ptr<leveldb::Iterator> it);
+    ~Iterator();
+
+    // Returns true if this iterator cannot advance any more.
+    bool IsAtEnd() const;
+
+    // Returns the entry currently pointed by this object.
+    const ResourceEntry& Get() const;
+
+    // Advances to the next entry.
+    void Advance();
+
+    // Returns true if this object has encountered any error.
+    bool HasError() const;
+
+   private:
+    ResourceEntry entry_;
+    scoped_ptr<leveldb::Iterator> it_;
+
+    DISALLOW_COPY_AND_ASSIGN(Iterator);
+  };
+
   explicit ResourceMetadataStorage(const base::FilePath& directory_path);
   virtual ~ResourceMetadataStorage();
 
   // Initializes this object.
   bool Initialize();
 
   // Sets the largest changestamp.
   bool SetLargestChangestamp(int64 largest_changestamp);
 
   // Gets the largest changestamp.
   int64 GetLargestChangestamp();
 
   // Puts the entry to this storage.
   bool PutEntry(const ResourceEntry& entry);
 
   // Returns an entry stored in this storage.
   scoped_ptr<ResourceEntry> GetEntry(const std::string& resource_id);
 
   // Removes an entry from this storage.
   bool RemoveEntry(const std::string& resource_id);
 
-  // Iterates over entries stored in this storage.
-  void Iterate(const IterateCallback& callback);
+  // Returns an object to iterate over entries stored in this storage.
+  scoped_ptr<Iterator> GetIterator();
 
   // Returns resource ID of the parent's child.
   std::string GetChild(const std::string& parent_resource_id,
                        const std::string& child_name);
 
   // Returns resource IDs of the parent's children.
   void GetChildren(const std::string& parent_resource_id,
                    std::vector<std::string>* children);
 
  private:
@@ skipping 17 matching lines @@
 
   // Entries stored in this storage.
   scoped_ptr<leveldb::DB> resource_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourceMetadataStorage);
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_RESOURCE_METADATA_STORAGE_H_