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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_LOCAL_FILE_SYNC_STATUS_H_
      6 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_LOCAL_FILE_SYNC_STATUS_H_
      7 
      8 #include <map>
      9 #include <set>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/compiler_specific.h"
     13 #include "base/observer_list.h"
     14 #include "base/threading/non_thread_safe.h"
     15 #include "webkit/browser/fileapi/file_system_url.h"
     16 
     17 namespace fileapi {
     18 class FileSystemURL;
     19 }
     20 
     21 namespace sync_file_system {
     22 
     23 // Represents local file sync status.
     24 // This class is supposed to run only on IO thread.
     25 //
     26 // This class manages two important synchronization flags: writing (counter)
     27 // and syncing (flag).  Writing counter keeps track of which URL is in
     28 // writing and syncing flag indicates which URL is in syncing.
     29 //
     30 // An entry can have multiple writers but sync is exclusive and cannot overwrap
     31 // with any writes or syncs.
     32 class LocalFileSyncStatus
     33     : public base::NonThreadSafe {
     34  public:
     35   class Observer {
     36    public:
     37     Observer() {}
     38     virtual ~Observer() {}
     39     virtual void OnSyncEnabled(const fileapi::FileSystemURL& url) = 0;
     40     virtual void OnWriteEnabled(const fileapi::FileSystemURL& url) = 0;
     41    private:
     42     DISALLOW_COPY_AND_ASSIGN(Observer);
     43   };
     44 
     45   LocalFileSyncStatus();
     46   ~LocalFileSyncStatus();
     47 
     48   // Increment writing counter for |url|.
     49   // This should not be called if the |url| is not writable.
     50   void StartWriting(const fileapi::FileSystemURL& url);
     51 
     52   // Decrement writing counter for |url|.
     53   void EndWriting(const fileapi::FileSystemURL& url);
     54 
     55   // Start syncing for |url| and disable writing.
     56   // This should not be called if |url| is in syncing or in writing.
     57   void StartSyncing(const fileapi::FileSystemURL& url);
     58 
     59   // Clears the syncing flag for |url| and enable writing.
     60   void EndSyncing(const fileapi::FileSystemURL& url);
     61 
     62   // Returns true if the |url| or its parent or child is in writing.
     63   bool IsWriting(const fileapi::FileSystemURL& url) const;
     64 
     65   // Returns true if the |url| is enabled for writing (i.e. not in syncing).
     66   bool IsWritable(const fileapi::FileSystemURL& url) const;
     67 
     68   // Returns true if the |url| is enabled for syncing (i.e. neither in
     69   // syncing nor writing).
     70   bool IsSyncable(const fileapi::FileSystemURL& url) const;
     71 
     72   void AddObserver(Observer* observer);
     73   void RemoveObserver(Observer* observer);
     74 
     75  private:
     76   typedef std::map<fileapi::FileSystemURL,int64,
     77                    fileapi::FileSystemURL::Comparator> URLCountMap;
     78 
     79   bool IsChildOrParentWriting(const fileapi::FileSystemURL& url) const;
     80   bool IsChildOrParentSyncing(const fileapi::FileSystemURL& url) const;
     81 
     82   // If this count is non-zero positive there're ongoing write operations.
     83   URLCountMap writing_;
     84 
     85   // If this flag is set sync process is running on the file.
     86   fileapi::FileSystemURLSet syncing_;
     87 
     88   ObserverList<Observer> observer_list_;
     89 
     90   DISALLOW_COPY_AND_ASSIGN(LocalFileSyncStatus);
     91 };
     92 
     93 }  // namespace sync_file_system
     94 
     95 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_LOCAL_FILE_SYNC_STATUS_H_
     96