Process A leave MemoryMapFile available for Process B

Question

Been Googling, but can't find an answer to this. Have not used MemoryMappedFile before. Have just been reading about them with a view to implementing basic IPC. Before I invest time prototyping can anyone tell me whether the following logic will work?

I had in mind to use a non-persisted memory-mapped file, so that it is automatically cleaned up after use.

1. Process A opens MemoryMappedFile and writes to it.
2. Process A launches process B
3. Process A quits
4. Process B performs OpenExisting on MemoryMappedFile created by process A
5. Process B reads data from MemoryMappedFile and does processing...

Process A & B will both know the name of the file.

Will the file created by Process A remain until process B has disposed of it?

What are the mechanics, should process A not Dispose the file and let Process B do that?

If this logic will not work then I was considering that Process A wait for Process B to complete, but this is not ideal.

Thanks for any shedding of light ;)

Answer 1

That will work, except process B needs to open a handle to the memory mapped file before process A closes its handle. The reason is that the memory mapped file is destroyed when the last handle is closed.

(I assume we're talking Windows here.)

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Edit: I got interested in this and did a bit more reading…

Probably the most correct and robust way to do this would be for process B to inherit a handle to to the memory mapping. Some links:

• Handle Inheritance in Windows
• Programmatically controlling which handles are inherited by new processes in Win32
• How do I pass a lot of data to a process when it starts up?

I think this last link provides you with a model answer by one of the most knowledgeable Windows programmers in the world. Do read the comments below the article as well.