Improve reliability of custom spelling dictionary file.

chrome/browser/spellchecker/spellcheck_custom_dictionary.h

 // Copyright (c) 2012 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_SPELLCHECKER_SPELLCHECK_CUSTOM_DICTIONARY_H_
 #define CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_CUSTOM_DICTIONARY_H_
 
 #include <string>
 #include <vector>
 
 #include "base/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "chrome/browser/spellchecker/spellcheck_dictionary.h"
 #include "chrome/common/spellcheck_common.h"
 
-// Defines a custom dictionary which users can add their own words to.
+// Defines a custom dictionary where users can add their own words. All words
+// must be UTF8, between 1 and 128 bytes long, and without ASCII whitespace.
+// The dictionary contains its own checksum when saved on disk. Example
+// dictionary file contents:
+//
+//   bar
+//   foo
+//   checksum_v1 = ec3df4034567e59e119fcf87f2d9bad4
+//
 class SpellcheckCustomDictionary : public SpellcheckDictionary {
  public:
   class Observer {
    public:
     virtual void OnCustomDictionaryLoaded() = 0;
     virtual void OnCustomDictionaryWordAdded(const std::string& word) = 0;
     virtual void OnCustomDictionaryWordRemoved(const std::string& word) = 0;
   };
 
   explicit SpellcheckCustomDictionary(Profile* profile);
   virtual ~SpellcheckCustomDictionary();
 
   // Overridden from SpellcheckDictionary:
   virtual void Load() OVERRIDE;
 
   const chrome::spellcheck_common::WordList& GetWords() const;
 
   // Populates the |custom_words| with the list of words in the custom
-  // dictionary file. Makes sure that the custom dictionary file is sorted and
-  // does not have duplicates.
+  // dictionary file. Makes sure that the custom dictionary file is sorted, does
+  // not have duplicates, and contains only valid words.
   void LoadDictionaryIntoCustomWordList(
       chrome::spellcheck_common::WordList* custom_words);
 
   // Moves the words from the |custom_words| argument into its own private
   // member variable. Does not delete the memory at |custom_words|.
   void SetCustomWordList(chrome::spellcheck_common::WordList* custom_words);
 
-  // Adds the given word to the custom words list and inform renderer of the
-  // update. Returns false for duplicate words.
+  // Adds the given word to the custom words list and informs renderers of the
+  // update. Returns false for duplicate and invalid words.
   bool AddWord(const std::string& word);
 
   // Returns false for duplicate words.
   bool CustomWordAddedLocally(const std::string& word);
 
   void WriteWordToCustomDictionary(const std::string& word);
 
-  // Removes the given word from the custom words list and informs renderer of
-  // the update. Returns false for words that are not in the dictionary.
+  // Removes the given word from the custom words list and informs renderers of
+  // the update. Returns false for words that are not in the dictionary and
+  // invalid words.
   bool RemoveWord(const std::string& word);
 
   // Returns false for words that are not in the dictionary.
   bool CustomWordRemovedLocally(const std::string& word);
 
   void EraseWordFromCustomDictionary(const std::string& word);
 
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
  private:
   // Returns a newly allocated list of words read from custom dictionary file.
   // The caller owns this new list.
   chrome::spellcheck_common::WordList* LoadDictionary();
 
   // The reply point for PostTaskAndReplyWithResult. Called when LoadDictionary
   // is finished reading words from custom dictionary file. Moves the strings
   // from the |custom_words| argument into the private member variable |words_|
   // and deletes the memory at |custom_words|.
   void SetCustomWordListAndDelete(
       chrome::spellcheck_common::WordList* custom_words);
 
+  // Loads the dictionary file into |custom_words|. If the dictionary checksum
+  // is not valid, but backup checksum is valid, then restores the backup and
+  // loads that into |custom_words| instead. If the backup is invalid too, then
+  // clears |custom_words|.
+  void LoadDictionaryFileReliably(
+      chrome::spellcheck_common::WordList* custom_words);
+
+  // Backs up the original dictionary, saves |custom_words| and its checksum
+  // into the dictionary file.
+  void SaveDictionaryFileReliably(
+      const chrome::spellcheck_common::WordList& custom_words);
+
   // In-memory cache of the custom words file.
   chrome::spellcheck_common::WordList words_;
 
   // A path for custom dictionary per profile.
   FilePath custom_dictionary_path_;
 
   base::WeakPtrFactory<SpellcheckCustomDictionary> weak_ptr_factory_;
 
-  std::vector<Observer*> observers_;
+  ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(SpellcheckCustomDictionary);
 };
 
 #endif  // CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_CUSTOM_DICTIONARY_H_