Implement ID persistence for bookmarks:...

chrome/browser/bookmarks/bookmark_codec.h

 // Copyright (c) 2006-2008 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.
 
 // BookmarkCodec is responsible for encoding and decoding the BookmarkModel
 // into JSON values. The encoded values are written to disk via the
 // BookmarkService.
 
 #ifndef CHROME_BROWSER_BOOKMARKS_BOOKMARK_CODEC_H_
 #define CHROME_BROWSER_BOOKMARKS_BOOKMARK_CODEC_H_
 
+#include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/md5.h"
 
 class BookmarkModel;
 class BookmarkNode;
 class DictionaryValue;
 class ListValue;
 class Value;
 
+// Utility class to help assign unique integer IDs.
+class UniqueIDGenerator {
+ public:
+  UniqueIDGenerator();
+
+  // Checks whether the given ID can be used as a unique ID or not. If it can,
+  // returns the id itself, otherwise generates a new unique id in a simple way
+  // and returns that.
+  // NOTE that if id is 0, a new unique id is returned.
+  int GetUniqueID(int id);
+
+  // Resets the ID generator to initial state.
+  void Reset();
+
+  // Returns the current maximum.
+  int current_max() const { return current_max_; }
+
+ private:
+  // Maximum value we have seen so far.
+  int current_max_;
+  // All IDs assigned so far.
+  std::set<int> assigned_ids_;
+
+  DISALLOW_COPY_AND_ASSIGN(UniqueIDGenerator);
+};
+
 // BookmarkCodec is responsible for encoding/decoding bookmarks into JSON
 // values. BookmarkCodec is used by BookmarkService.
 
 class BookmarkCodec {
  public:
-  BookmarkCodec() {}
+  // Creates an instance of the codec. Encodes/decodes bookmark IDs also if
+  // persist_ids is true. The default constructor will not encode/decode IDs.
+  // During decoding, if persist_ids is true and if the IDs in the file are not
+  // unique, we will reassign IDs to make them unique. There are no guarantees
+  // on how the IDs are reassigned or about doing minimal reassignments to
+  // achieve uniqueness.
+  BookmarkCodec();
+  explicit BookmarkCodec(bool persist_ids);
 
   // Encodes the model to a JSON value. It's up to the caller to delete the
   // returned object. This is invoked to encode the contents of the bookmark bar
   // model and is currently a convenience to invoking Encode that takes the
   // bookmark bar node and other folder node.
   Value* Encode(BookmarkModel* model);
 
   // Encodes the bookmark bar and other folders returning the JSON value. It's
   // up to the caller to delete the returned object.
   // This method is public for use by StarredURLDatabase in migrating the
@@ skipping 16 matching lines @@
   // differ from the stored checksum if the file contents were changed by the
   // user.
   const std::string& stored_checksum() const { return stored_checksum_; }
 
   // Names of the various keys written to the Value.
   static const wchar_t* kRootsKey;
   static const wchar_t* kRootFolderNameKey;
   static const wchar_t* kOtherBookmarFolderNameKey;
   static const wchar_t* kVersionKey;
   static const wchar_t* kChecksumKey;
+  static const wchar_t* kIdKey;
   static const wchar_t* kTypeKey;
   static const wchar_t* kNameKey;
   static const wchar_t* kDateAddedKey;
   static const wchar_t* kURLKey;
   static const wchar_t* kDateModifiedKey;
   static const wchar_t* kChildrenKey;
 
   // Possible values for kTypeKey.
   static const wchar_t* kTypeURL;
   static const wchar_t* kTypeFolder;
@@ skipping 21 matching lines @@
 
   // Updates the check-sum with the given string.
   void UpdateChecksum(const std::string& str);
   void UpdateChecksum(const std::wstring& str);
 
   // Updates the check-sum with the given contents of URL/folder bookmark node.
   // NOTE: These functions take in individual properties of a bookmark node
   // instead of taking in a BookmarkNode for efficiency so that we don't convert
   // varous data-types to wide strings multiple times - once for serializing
   // and once for computing the check-sum.
-  void UpdateChecksumWithUrlNode(const std::wstring& title,
+  void UpdateChecksumWithUrlNode(const std::string& id,
+                                 const std::wstring& title,
                                  const std::wstring& url);
-  void UpdateChecksumWithFolderNode(const std::wstring& title);
+  void UpdateChecksumWithFolderNode(const std::string& id,
+                                    const std::wstring& title);
 
   // Initializes/Finalizes the checksum.
   void InitializeChecksum();
   void FinalizeChecksum();
 
+  // Whether to persist IDs or not.
+  bool persist_ids_;
+  // Unique ID generator used during decoding.
+  UniqueIDGenerator id_generator_;
+
   // MD5 context used to compute MD5 hash of all bookmark data.
   MD5Context md5_context_;
 
   // Checksums.
   std::string computed_checksum_;
   std::string stored_checksum_;
 
-
   DISALLOW_COPY_AND_ASSIGN(BookmarkCodec);
 };
 
 #endif  // CHROME_BROWSER_BOOKMARKS_BOOKMARK_CODEC_H_