TAO/tao/Storable_File_Guard.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file   Storable_File_Guard.h
   6  *
   7  *  @author Rich Seibel (seibelr@ociweb.com)
   8  *  @author Byron Harris (harrisb@ociweb.com)
   9  */
  10 //=============================================================================
  11
  12 #ifndef TAO_STORABLE_FILE_GUARD_H
  13 #define TAO_STORABLE_FILE_GUARD_H
  14
  15 #include "tao/Storable_Base.h"
  16
  17 TAO_BEGIN_VERSIONED_NAMESPACE_DECL
  18
  19 namespace TAO
  20 {
  21   /**
  22    * @class Storable_File_Guard
  23    * @brief Base class to use with TAO_Storable_Base to synch object state
  24    * with a storable base.
  25    *
  26    * A guard for Storable_Base that opens a file
  27    * for read/write and sets a lock on it. It then checks if the file has
  28    * changed and re-reads it if it has.
  29    *
  30    */
  31   class TAO_Export Storable_File_Guard
  32   {
  33   public:
  34     Storable_File_Guard (bool redundant,
  35                          bool use_backup = Storable_Base::use_backup_default);
  36
  37     virtual ~Storable_File_Guard () noexcept(false);
  38
  39     /// Releases the lock, closes the file, and deletes the I/O stream.
  40     /// Destructors of derived classes should call this this will
  41     /// virtual functions are available.
  42     void release (void);
  43
  44     /// Return when the object in memory has last changed
  45     virtual time_t get_object_last_changed () = 0;
  46
  47     /// Get the underlying stream being used.
  48     TAO::Storable_Base & peer ();
  49
  50     /// Indicate how the state of the object is being used.
  51     /// This is used for determine the mode for accessing
  52     /// the persistent store.
  53     enum Method_Type
  54     {
  55
  56       /// Construction with persistent file already existing
  57       CREATE_WITH_FILE,
  58
  59       /// Construction with persistent file not existing
  60       CREATE_WITHOUT_FILE,
  61
  62       /// Getting object state
  63       ACCESSOR,
  64
  65       /// Setting object state
  66       MUTATOR
  67     };
  68
  69   protected:
  70     /// Should be called by constructors of derived classes
  71     /// since can't call the virtual functions below in constructor
  72     /// of this class.
  73     void init (Method_Type method_type);
  74
  75     /// Initializes the backing store file object but does not
  76     /// actually load the data. This can be called without locks,
  77     /// allowing the caller to decide whether or not to then lock
  78     /// and complete the load.
  79     void init_no_load (Method_Type method_type);
  80
  81     /// Complete the initialization of the containing object, should
  82     /// be called with lock held after calling init_no_load
  83     void reload (void);
  84
  85     /// Check if the object is current with the last update.
  86     virtual bool object_obsolete (void);
  87
  88     /// Mark the object as up to date
  89     virtual void mark_object_current (void);
  90
  91     /// Indicate when the object in memory has last changed
  92     virtual void set_object_last_changed (const time_t & time) = 0;
  93
  94     /// Load object from file to memory. Return 0 on success.
  95     virtual int load_from_stream () = 0;
  96
  97     /// Answer if object has been loaded from file
  98     virtual bool is_loaded_from_stream () = 0;
  99
 100     virtual Storable_Base * create_stream (const char * mode) = 0;
 101
 102     /// The pointer to the actual file I/O (bridge pattern)
 103     Storable_Base *fl_;
 104
 105   private:
 106     // Return 0 if successful.
 107     int load ();
 108
 109     bool redundant_;
 110
 111     /// A flag to keep us from trying to close things more than once.
 112     int closed_;
 113
 114     /// The flags that we were opened with
 115     int rwflags_;
 116
 117     /// A flag indicating if backup/restore should be performed
 118     bool use_backup_;
 119
 120     /// Symbolic values for the flags in the above
 121     enum { mode_write = 1, mode_read = 2, mode_create = 4 };
 122   };
 123 }
 124
 125 TAO_END_VERSIONED_NAMESPACE_DECL
 126
 127 #endif