Makes the tab restore service persist closed tabs/windows to disk and

reload them when asked.

Sorry for largish looking change. It's made big by refactoring common
code between TabRestoreService and SessionService into a common
superclass. At the same time I removed some dead code and shuffled the
session related classes into a single directory for easier perusal.

BUG=384
TEST=close the browser, start the browser and make sure the new tab
     page shows closed windows/tabs from the previous session.

Review URL: http://codereview.chromium.org/13152

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@6490 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 122 insertions, 0 deletions

diff --git a/chrome/browser/sessions/session_backend.h b/chrome/browser/sessions/session_backend.h
new file mode 100644
index 0000000..1519d3f
--- /dev/null
+++ b/chrome/browser/sessions/session_backend.h
@@ -0,0 +1,122 @@
+// 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.
+
+#ifndef CHROME_BROWSER_SESSIONS_SESSION_BACKEND_H_
+#define CHROME_BROWSER_SESSIONS_SESSION_BACKEND_H_
+
+#include <vector>
+
+#include "base/ref_counted.h"
+#include "base/scoped_handle.h"
+#include "chrome/browser/sessions/base_session_service.h"
+#include "chrome/browser/sessions/session_command.h"
+
+class Pickle;
+
+// SessionBackend -------------------------------------------------------------
+
+// SessionBackend is the backend used by BaseSessionService. It is responsible
+// for maintaining two files:
+// . The current file, which is the file commands passed to AppendCommands
+//   get written to.
+// . The last file. When created the current file is moved to the last
+//   file.
+//
+// Each file contains an arbitrary set of commands supplied from
+// BaseSessionService. A command consists of a unique id and a stream of bytes.
+// SessionBackend does not use the id in anyway, that is used by
+// BaseSessionService.
+class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
+ public:
+  typedef SessionCommand::id_type id_type;
+  typedef SessionCommand::size_type size_type;
+
+  // Initial size of the buffer used in reading the file. This is exposed
+  // for testing.
+  static const int kFileReadBufferSize;
+
+  // Creates a SessionBackend. This method is invoked on the MAIN thread,
+  // and does no IO. The real work is done from Init, which is invoked on
+  // the file thread.
+  //
+  // |path_to_dir| gives the path the files are written two, and |type|
+  // indicates which service is using this backend. |type| is used to determine
+  // the name of the files to use as well as for logging.
+  SessionBackend(BaseSessionService::SessionType type,
+                 const std::wstring& path_to_dir);
+
+  // Moves the current file to the last file, and recreates the current file.
+  //
+  // NOTE: this is invoked before every command, and does nothing if we've
+  // already Init'ed.
+  void Init();
+
+  // Appends the specified commands to the current file. If reset_first is
+  // true the the current file is recreated.
+  //
+  // NOTE: this deletes SessionCommands in commands as well as the supplied
+  // vector.
+  void AppendCommands(std::vector<SessionCommand*>* commands,
+                      bool reset_first);
+
+  // Invoked from the service to read the commands that make up the last
+  // session, invokes ReadSessionImpl to do the work.
+  void ReadLastSessionCommands(
+      scoped_refptr<BaseSessionService::InternalGetCommandsRequest> request);
+
+  // Reads the commands from the last file.
+  //
+  // On success, the read commands are added to commands. It is up to the
+  // caller to delete the commands.
+  bool ReadLastSessionCommandsImpl(std::vector<SessionCommand*>* commands);
+
+  // Deletes the file containing the commands for the last session.
+  void DeleteLastSession();
+
+  // Moves the current session to the last and resets the current. This is
+  // called during startup and if the user launchs the app and no tabbed
+  // browsers are running.
+  void MoveCurrentSessionToLastSession();
+
+ private:
+  // Recreates the current file such that it only contains the header and
+  // NO commands.
+  void ResetFile();
+
+  // Opens the current file and writes the header. On success a handle to
+  // the file is returned.
+  HANDLE OpenAndWriteHeader(const std::wstring& path);
+
+  // Appends the specified commands to the specified file.
+  bool AppendCommandsToFile(HANDLE handle,
+                            const std::vector<SessionCommand*>& commands);
+
+  const BaseSessionService::SessionType type_;
+
+  // Returns the path to the last file.
+  std::wstring GetLastSessionPath();
+
+  // Returns the path to the current file.
+  std::wstring GetCurrentSessionPath();
+
+  // Directory files are relative to.
+  const std::wstring path_to_dir_;
+
+  // Whether the previous target file is valid.
+  bool last_session_valid_;
+
+  // Handle to the target file.
+  ScopedHandle current_session_handle_;
+
+  // Whether we've inited. Remember, the constructor is run on the
+  // Main thread, all others on the IO thread, hence lazy initialization.
+  bool inited_;
+
+  // If true, the file is empty (no commands have been added to it).
+  bool empty_file_;
+
+  DISALLOW_COPY_AND_ASSIGN(SessionBackend);
+};
+
+#endif  // #define CHROME_BROWSER_SESSIONS_SESSION_BACKEND_H_