Memory Mapped File Access

Robert robert.muench at
Sat May 29 12:52:28 PDT 2010

On 2010-05-29 18:30:13 +0200, Andrei Alexandrescu 
<SeeWebsiteForEmail at> said:

>> Andrei and I had talked a while back about adding memory-mapped file
>> support to the GC and then it fell off the radar while we worked on
>> other things.  I'll see if I can remember how it was to work.
> The basic idea is that the only way to handle memory-mapped files 
> safely is to let the garbage collector close them. This is because in 
> any other case you'd have dangling pointers.

Ok, that makes sense. On the other hand I will use a very simple 
rule-of-thumb: As long as the app runs the file is open. Only if the 
app terminates the file gets closed.

Which implies that the reference to the MMF is a global but this 
shouldn't be a problem.

> So the idea is that druntime should provide a safe means for mapping a 
> file to memory and an unsafe means of closing a file.

Why should it provide an unsafe way of closing a MMF file?

> Safe code should be able to count on the garbage collector to close 
> memory-mapped files that have no pointers referring to them.

Have you sketched any ideas how to use the GC for MMF?

Robert M. Münch

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