CSharedMemoryObject

$Revision: 3 $

Description

This class allows you to create shared memory objects easily. A shared memory segment is a chunk of memory that is shared between multiple processes in a system. Shared memory is great for things like holding status information. For example, you could have a process that reads position information from a GPS unit and puts it into shared memory. You could have many other applications connect to that shared memory and read the position data.

Data Members

None.

Methods

void Close( void ): Closes the object. You can no longer use the pointer.
BOOL Create( const CString& object_name, DWORD size_in_bytes ): Creates a shared memory object. If the object specified by object_name already exists, you will attach to it. In other words, when Create() returns TRUE, you will have a shared memory object whether it was newly created or attached to an existing one.
void GetName( CString& object_name ) const: Returns the name of the shared memory object.
void * GetPointer( void ) const: Returns the pointer to the shared memory segment. It will return NULL if Create() has not yet been called.
DWORD GetSize( void ) const: Returns the size in bytes fo the shared memory object. It will return zero if Create() has not yet been called.

Example

#include <wfc.h>
#pragma hdrstop

void update_time( constCString& queue_name )
{
   WFCTRACEINIT( TEXT( "update_time()" ) );

   CSharedMemoryObject queue;

   if ( queue.Create( queue_name, sizeof( APPLICATION_QUEUE ) != FALSE )
   {
      APPLICATION_QUEUE * queue_p = NULL;

      queue_p = (APPLICATION_QUEUE *) queue.GetPointer();

      if ( queue_p != NULL )
      {
         CSystemTime system_time;

         system_time.Get();

         queue_p->last_updated = system_time;
      }
   }
}

API's Used

CloseHandle
CreateFileMapping
GetLastError
MapViewOfFile
UnmapViewOfFile

Copyright, 2000, Samuel R. Blackburn
$Workfile: CSharedMemoryObject.cpp $
$Modtime: 1/17/00 9:21a $