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 ();
  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       /// Construction with persistent file already existing
  56       CREATE_WITH_FILE,
  57
  58       /// Construction with persistent file not existing
  59       CREATE_WITHOUT_FILE,
  60
  61       /// Getting object state
  62       ACCESSOR,
  63
  64       /// Setting object state
  65       MUTATOR
  66     };
  67
  68   protected:
  69     /// Should be called by constructors of derived classes
  70     /// since can't call the virtual functions below in constructor
  71     /// of this class.
  72     void init (Method_Type method_type);
  73
  74     /// Initializes the backing store file object but does not
  75     /// actually load the data. This can be called without locks,
  76     /// allowing the caller to decide whether or not to then lock
  77     /// and complete the load.
  78     void init_no_load (Method_Type method_type);
  79
  80     /// Complete the initialization of the containing object, should
  81     /// be called with lock held after calling init_no_load
  82     void reload ();
  83
  84     /// Check if the object is current with the last update.
  85     virtual bool object_obsolete ();
  86
  87     /// Mark the object as up to date
  88     virtual void mark_object_current ();
  89
  90     /// Indicate when the object in memory has last changed
  91     virtual void set_object_last_changed (const time_t & time) = 0;
  92
  93     /// Load object from file to memory. Return 0 on success.
  94     virtual int load_from_stream () = 0;
  95
  96     /// Answer if object has been loaded from file
  97     virtual bool is_loaded_from_stream () = 0;
  98
  99     virtual Storable_Base * create_stream (const char * mode) = 0;
 100
 101     /// The pointer to the actual file I/O (bridge pattern)
 102     Storable_Base *fl_;
 103
 104   private:
 105     // Return 0 if successful.
 106     int load ();
 107
 108     bool redundant_;
 109
 110     /// A flag to keep us from trying to close things more than once.
 111     int closed_;
 112
 113     /// The flags that we were opened with
 114     int rwflags_;
 115
 116     /// A flag indicating if backup/restore should be performed
 117     bool use_backup_;
 118
 119     /// Symbolic values for the flags in the above
 120     enum { mode_write = 1, mode_read = 2, mode_create = 4 };
 121   };
 122 }
 123
 124 TAO_END_VERSIONED_NAMESPACE_DECL
 125
 126 #endif