components/sessions/session_backend.h

   1 // Copyright 2011 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 COMPONENTS_SESSIONS_SESSION_BACKEND_H_
   6 #define COMPONENTS_SESSIONS_SESSION_BACKEND_H_
   7
   8 #include <vector>
   9
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/task/cancelable_task_tracker.h"
  13 #include "components/sessions/base_session_service.h"
  14 #include "components/sessions/session_command.h"
  15
  16 namespace base {
  17 class File;
  18 }
  19
  20 namespace sessions {
  21 // SessionBackend -------------------------------------------------------------
  22
  23 // SessionBackend is the backend used by BaseSessionService. It is responsible
  24 // for maintaining two files:
  25 // . The current file, which is the file commands passed to AppendCommands
  26 //   get written to.
  27 // . The last file. When created the current file is moved to the last
  28 //   file.
  29 //
  30 // Each file contains an arbitrary set of commands supplied from
  31 // BaseSessionService. A command consists of a unique id and a stream of bytes.
  32 // SessionBackend does not use the id in anyway, that is used by
  33 // BaseSessionService.
  34 class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
  35  public:
  36   typedef sessions::SessionCommand::id_type id_type;
  37   typedef sessions::SessionCommand::size_type size_type;
  38
  39   // Initial size of the buffer used in reading the file. This is exposed
  40   // for testing.
  41   static const int kFileReadBufferSize;
  42
  43   // Creates a SessionBackend. This method is invoked on the MAIN thread,
  44   // and does no IO. The real work is done from Init, which is invoked on
  45   // the file thread.
  46   //
  47   // |path_to_dir| gives the path the files are written two, and |type|
  48   // indicates which service is using this backend. |type| is used to determine
  49   // the name of the files to use as well as for logging.
  50   SessionBackend(sessions::BaseSessionService::SessionType type,
  51                  const base::FilePath& path_to_dir);
  52
  53   // Moves the current file to the last file, and recreates the current file.
  54   //
  55   // NOTE: this is invoked before every command, and does nothing if we've
  56   // already Init'ed.
  57   void Init();
  58   bool inited() const { return inited_; }
  59
  60   // Appends the specified commands to the current file. If reset_first is
  61   // true the the current file is recreated.
  62   void AppendCommands(ScopedVector<sessions::SessionCommand> commands,
  63                       bool reset_first);
  64
  65   // Invoked from the service to read the commands that make up the last
  66   // session, invokes ReadLastSessionCommandsImpl to do the work.
  67   void ReadLastSessionCommands(
  68       const base::CancelableTaskTracker::IsCanceledCallback& is_canceled,
  69       const sessions::BaseSessionService::GetCommandsCallback& callback);
  70
  71   // Reads the commands from the last file.
  72   //
  73   // On success, the read commands are added to commands.
  74   bool ReadLastSessionCommandsImpl(
  75       ScopedVector<sessions::SessionCommand>* commands);
  76
  77   // Deletes the file containing the commands for the last session.
  78   void DeleteLastSession();
  79
  80   // Moves the current session to the last and resets the current. This is
  81   // called during startup and if the user launchs the app and no tabbed
  82   // browsers are running.
  83   void MoveCurrentSessionToLastSession();
  84
  85   // Reads the commands from the current file.
  86   //
  87   // On success, the read commands are added to commands. It is up to the
  88   // caller to delete the commands.
  89   bool ReadCurrentSessionCommandsImpl(
  90       ScopedVector<sessions::SessionCommand>* commands);
  91
  92  private:
  93   friend class base::RefCountedThreadSafe<SessionBackend>;
  94
  95   ~SessionBackend();
  96
  97   // If current_session_file_ is open, it is truncated so that it is essentially
  98   // empty (only contains the header). If current_session_file_ isn't open, it
  99   // is is opened and the header is written to it. After this
 100   // current_session_file_ contains no commands.
 101   // NOTE: current_session_file_ may be NULL if the file couldn't be opened or
 102   // the header couldn't be written.
 103   void ResetFile();
 104
 105   // Opens the current file and writes the header. On success a handle to
 106   // the file is returned.
 107   base::File* OpenAndWriteHeader(const base::FilePath& path);
 108
 109   // Appends the specified commands to the specified file.
 110   bool AppendCommandsToFile(
 111       base::File* file,
 112       const ScopedVector<sessions::SessionCommand>& commands);
 113
 114   const sessions::BaseSessionService::SessionType type_;
 115
 116   // Returns the path to the last file.
 117   base::FilePath GetLastSessionPath();
 118
 119   // Returns the path to the current file.
 120   base::FilePath GetCurrentSessionPath();
 121
 122   // Directory files are relative to.
 123   const base::FilePath path_to_dir_;
 124
 125   // Whether the previous target file is valid.
 126   bool last_session_valid_;
 127
 128   // Handle to the target file.
 129   scoped_ptr<base::File> current_session_file_;
 130
 131   // Whether we've inited. Remember, the constructor is run on the
 132   // Main thread, all others on the IO thread, hence lazy initialization.
 133   bool inited_;
 134
 135   // If true, the file is empty (no commands have been added to it).
 136   bool empty_file_;
 137
 138   DISALLOW_COPY_AND_ASSIGN(SessionBackend);
 139 };
 140
 141 }  // namespace sessions
 142
 143 #endif  // COMPONENTS_SESSIONS_SESSION_BACKEND_H_