chrome/browser/sessions/session_backend.h

   1 // Copyright (c) 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 CHROME_BROWSER_SESSIONS_SESSION_BACKEND_H_
   6 #define CHROME_BROWSER_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 "chrome/browser/sessions/base_session_service.h"
  14 #include "chrome/browser/sessions/session_command.h"
  15
  16 namespace base {
  17 class File;
  18 }
  19
  20 // SessionBackend -------------------------------------------------------------
  21
  22 // SessionBackend is the backend used by BaseSessionService. It is responsible
  23 // for maintaining two files:
  24 // . The current file, which is the file commands passed to AppendCommands
  25 //   get written to.
  26 // . The last file. When created the current file is moved to the last
  27 //   file.
  28 //
  29 // Each file contains an arbitrary set of commands supplied from
  30 // BaseSessionService. A command consists of a unique id and a stream of bytes.
  31 // SessionBackend does not use the id in anyway, that is used by
  32 // BaseSessionService.
  33 class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
  34  public:
  35   typedef SessionCommand::id_type id_type;
  36   typedef SessionCommand::size_type size_type;
  37
  38   // Initial size of the buffer used in reading the file. This is exposed
  39   // for testing.
  40   static const int kFileReadBufferSize;
  41
  42   // Creates a SessionBackend. This method is invoked on the MAIN thread,
  43   // and does no IO. The real work is done from Init, which is invoked on
  44   // the file thread.
  45   //
  46   // |path_to_dir| gives the path the files are written two, and |type|
  47   // indicates which service is using this backend. |type| is used to determine
  48   // the name of the files to use as well as for logging.
  49   SessionBackend(BaseSessionService::SessionType type,
  50                  const base::FilePath& path_to_dir);
  51
  52   // Moves the current file to the last file, and recreates the current file.
  53   //
  54   // NOTE: this is invoked before every command, and does nothing if we've
  55   // already Init'ed.
  56   void Init();
  57   bool inited() const { return inited_; }
  58
  59   // Appends the specified commands to the current file. If reset_first is
  60   // true the the current file is recreated.
  61   //
  62   // NOTE: this deletes SessionCommands in commands as well as the supplied
  63   // vector.
  64   void AppendCommands(std::vector<SessionCommand*>* commands,
  65                       bool reset_first);
  66
  67   // Invoked from the service to read the commands that make up the last
  68   // session, invokes ReadLastSessionCommandsImpl to do the work.
  69   void ReadLastSessionCommands(
  70       const base::CancelableTaskTracker::IsCanceledCallback& is_canceled,
  71       const BaseSessionService::InternalGetCommandsCallback& callback);
  72
  73   // Reads the commands from the last file.
  74   //
  75   // On success, the read commands are added to commands. It is up to the
  76   // caller to delete the commands.
  77   bool ReadLastSessionCommandsImpl(std::vector<SessionCommand*>* commands);
  78
  79   // Deletes the file containing the commands for the last session.
  80   void DeleteLastSession();
  81
  82   // Moves the current session to the last and resets the current. This is
  83   // called during startup and if the user launchs the app and no tabbed
  84   // browsers are running.
  85   void MoveCurrentSessionToLastSession();
  86
  87   // Reads the commands from the current file.
  88   //
  89   // On success, the read commands are added to commands. It is up to the
  90   // caller to delete the commands.
  91   bool ReadCurrentSessionCommandsImpl(std::vector<SessionCommand*>* commands);
  92
  93  private:
  94   friend class base::RefCountedThreadSafe<SessionBackend>;
  95
  96   ~SessionBackend();
  97
  98   // If current_session_file_ is open, it is truncated so that it is essentially
  99   // empty (only contains the header). If current_session_file_ isn't open, it
 100   // is is opened and the header is written to it. After this
 101   // current_session_file_ contains no commands.
 102   // NOTE: current_session_file_ may be NULL if the file couldn't be opened or
 103   // the header couldn't be written.
 104   void ResetFile();
 105
 106   // Opens the current file and writes the header. On success a handle to
 107   // the file is returned.
 108   base::File* OpenAndWriteHeader(const base::FilePath& path);
 109
 110   // Appends the specified commands to the specified file.
 111   bool AppendCommandsToFile(base::File* file,
 112                             const std::vector<SessionCommand*>& commands);
 113
 114   const 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 #endif  // CHROME_BROWSER_SESSIONS_SESSION_BACKEND_H_