components/sessions/session_command.h

   1 // Copyright 2006 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_COMMAND_H_
   6 #define COMPONENTS_SESSIONS_SESSION_COMMAND_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "components/sessions/sessions_export.h"
  12
  13 namespace base {
  14 class Pickle;
  15 }
  16
  17 namespace sessions {
  18
  19 // SessionCommand contains a command id and arbitrary chunk of data. The id
  20 // and chunk of data are specific to the service creating them.
  21 //
  22 // Both TabRestoreService and SessionService use SessionCommands to represent
  23 // state on disk.
  24 //
  25 // There are two ways to create a SessionCommand:
  26 // . Specifiy the size of the data block to create. This is useful for
  27 //   commands that have a fixed size.
  28 // . From a pickle, this is useful for commands whose length varies.
  29 class SESSIONS_EXPORT SessionCommand {
  30  public:
  31   // These get written to disk, so we define types for them.
  32   // Type for the identifier.
  33   typedef uint8 id_type;
  34
  35   // Type for writing the size.
  36   typedef uint16 size_type;
  37
  38   // Creates a session command with the specified id. This allocates a buffer
  39   // of size |size| that must be filled via contents().
  40   SessionCommand(id_type id, size_type size);
  41
  42   // Convenience constructor that creates a session command with the specified
  43   // id whose contents is populated from the contents of pickle.
  44   SessionCommand(id_type id, const base::Pickle& pickle);
  45
  46   // The contents of the command.
  47   char* contents() { return const_cast<char*>(contents_.c_str()); }
  48   const char* contents() const { return contents_.c_str(); }
  49
  50   // Identifier for the command.
  51   id_type id() const { return id_; }
  52
  53   // Size of data.
  54   size_type size() const { return static_cast<size_type>(contents_.size()); }
  55
  56   // Convenience for extracting the data to a target. Returns false if
  57   // count is not equal to the size of data this command contains.
  58   bool GetPayload(void* dest, size_t count) const;
  59
  60   // Returns the contents as a pickle. It is up to the caller to delete the
  61   // returned Pickle. The returned Pickle references the underlying data of
  62   // this SessionCommand. If you need it to outlive the command, copy the
  63   // pickle.
  64   base::Pickle* PayloadAsPickle() const;
  65
  66  private:
  67   const id_type id_;
  68   std::string contents_;
  69
  70   DISALLOW_COPY_AND_ASSIGN(SessionCommand);
  71 };
  72
  73 }  // namespace sessions
  74
  75 #endif  // COMPONENTS_SESSIONS_SESSION_COMMAND_H_