Re: [boost] Random Access to Files (RAF) - any interest ?

From: Olaf van der Spek (olafvdspek_at_[hidden])
Date: 2006-05-25 05:28:26

On 5/25/06, Slava, Alex <raf.devel_at_[hidden]> wrote:
> > ZFS on Solaris 10 has an extension to the the Posix lseek() flags, SEEK_DATA
> > and SEEK_HOLE.  It makes it easy to find the holes in your files.  I may be
> > wrong here but I don't think Linux supports this.
> >
> Sparce file handling was described in Kernighan book more then 20
> years ago. I think that most UNIX-systems produces "holes" by default
> (Linux do this on ext2/ext3 and XFS for sure). It is not a problem to
> RAF. It just ask a system to allocate space and it is not important
> whether the data allocated or "hole" created. when writing in the
> "hole" system will allocate blocks for a file. There may be a problem
> that there is no more space on device, exactly such case is descried
> in MSDN (using memory-maped file on sparce or comprressed file). We
> will just check for an error in such cases.

What about (avoiding) fragmentation?
I think a way to allocate the entire file at one time should be available.