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