Re: [boost] [interprocess][iostreams] trac#4234

Subject: Re: [boost] [interprocess][iostreams] trac#4234
From: Marsh Ray (marsh_at_[hidden])
Date: 2010-10-11 14:47:30

On 10/10/2010 08:31 PM, Domagoj Saric wrote:
>
>- AFAIK the POSIX 'anonymous
> inheritable' shared memory functionality is also available on Win32 -
> kernel-life time shared memory emulation with memory mapped files on
> Windows is also unnecessary. It can be either provided directly by
> bypassing the Win32 APIs using the native NT API (I volunteer to help
> with the implementation or can do it from scratch by myself)

Be aware that native API calls are not always documented and are subject 
to change.

> AFAICT the only thing the Win32 API lacks for this is
> getting the size of the mapped region which could perhaps be emulated
> by passing the size at the begining of the mapped region...

You might be able to do something with VirtualQueryEx, it fills in a 
MEMORY_BASIC_INFORMATION structure about a specified address.
http://msdn.microsoft.com/en-us/library/aa366907.aspx
http://msdn.microsoft.com/en-us/library/aa366775.aspx

This gives the base address and size of the page range with the same 
attributes. You can walk through the regions (I wouldn't assume that 
it's always going to be reported as one contiguous range) and total up 
the pages with the MEM_MAPPED type ("Indicates that the memory pages 
within the region are mapped into the view of a section.").

Just to ensure another mapped view isn't placed immediately after it, 
you might want to make a sort of guard page (with VirtualAllocEx) having 
some non-MEM_MAPPED type right at the end of the mapped view.

- Marsh