Using FileMapping on .NET as IPC

• Download demo project - 36.6 Kb

Introduction

.NET inter-process mechanisms are very slow. With some system calls, it becomes easy to use file mapping and that's the faster mechanism for IPC.

Classes

• MemMap

  This class encapsulates a file mapping zone with system page-file support. All you need to do is give it a name and size.

  Usage:

  'Process 1
  dim mem1 as MemMap=new MemMap("ZONE1",2048) 
  mem1.writeString(0,"String to share")
  
  'Process 2
  dim mem1 as MemMap=new MemMap("ZONE1",2048) 
  dim sharedString=mem1.readString(0)
  
  mem1.close() 'at the end of both programs

  This class handles the creation or reuse of file mapping within the "new" method and has methods for reading and writing integers and strings on a given offset.

  It gives also a locking function based on InterLockedExchanged with protection against process elimination while having holding a lock.

   

• MemChannel

  This class uses the MemMap class to implement a FIFO queue of strings. You can create any number of channels by simply giving different names to each one of them.

  Usage:

  'Process1
  dim cha1 as MemChannel=new MemChannel("CHANAME1") 
  cha1.putMsg("This is the message")
  
  'Process2
  dim cha1 as MemChannel=new MemChannel("CHANAME1") 
  msgbox cha1.getMsg()
  
  cha1.close() 'at the end of both programs

EXEs

• MServer.exe

  Example of a server reading from a channel.

• Client.exe

  Example of a client writing to a channel.

Points of interest

The sample programs included here runs at 250.000 msgs per second on a PIV 3 GHz. But they block each other while accessing the channel and the CPU is not 100% busy.

With MemMap class support, it becomes easy to implement other IPC mechanisms as shared Dictionaries.

History

• 25-06-2005 - First version.
• 20-01-2007 - Second version