[boost] Re: Re: IOStream mmap too restrictive?

From: Jonathan Turkanis (technews_at_[hidden])
Date: 2004-09-02 18:09:42

"Jonathan Graehl" <jonathan_at_[hidden]> wrote in message
news:413795B2.4080301_at_graehl.org...
>

> In any case it looks like this SetFileValidData for win32,

The docs say this works only for NTFS volumes. The description of the parameter
ValidDataLength says: "This parameter must be a positive value that is greater
than the current valid data length, but less than the current file size."

It looks like SetEndOffFile is the correct function. The remarks say: "This
function can be used to truncate or extend a file. If the file is extended, the
contents of the file between the old EOF position and the new position are not
defined."

> and ftruncate
> for POSIX, could be used by memmap.c to support automatic creation of an
> appropriately sized backing file in the constructor for mapped_file (and
> the constructor for mapped output files in the IO lib could expose
> this).

This could be useful.

> I still think a truncate/SetFileValidData wrapper would be nice
> for the filesystem lib.
>
> I'm willing to code this if people think it's a good idea.  It frees
> users from having to first create an empty file of the right length first.

I'm interested. It sounds like something people want for memory-mapped files.
But be careful reading those windows docs! ;-)

Jonathan