Re: [Boost-users] [iostreams] - Using sparse Windows files

Subject: Re: [Boost-users] [iostreams] - Using sparse Windows files
From: Byrne, Kevin (kevin_at_[hidden])
Date: 2013-10-10 17:34:24

Niall,

No apologies necessary. Your time and answer is valuable and much
appreciated. You don't always hear what you want, you hear what you need.
Hey wait.....that could be a song. :)

Kevin

On Wed, Oct 9, 2013 at 2:51 PM, Niall Douglas <s_sourceforge_at_[hidden]>wrote:

> On 7 Oct 2013 at 16:00, Byrne, Kevin wrote:
>
> > I am trying to write cross-platform Boost code that utilizes sparse files
> > on Windows7 and FreeBSD. I already have Windows code that creates and
> > accesses a sparse file. I am of the understanding that Boost code cannot
> > create a Windows7 sparse file for me so I am trying to create the file
> > using the Windows code and then replace my ReadFileEx() and WriteFileEx()
> > with Boost streams. I have had luck with using iostreams::file to access
> an
> > existing Windows sparse file but it fails when I have to read a sparse
> area
> > thinking it is at the end of the file. I tried creating a stream using an
> > existing HANDLE but was not successful in reading or writing file
> content.
> > Before I proceed further I thought I would ask first if Boost is capable
> of
> > using Windows7 sparse file technology. If it is capable I would
> appreciate
> > some guidance on how. I have done a bit of searching on the web with not
> > much helpful information.
>
> Supposedly a file marked with the sparse flag appears like a
> non-sparse file to normal file i/o functions. In theory, Boost
> shouldn't notice a difference.
>
> In practice, I'd guess this is not a well tested path of code. Even
> in AFIO which is intended for this sort of thing, I haven't bothered
> testing spare files. My main rationale: ReFS drops sparse file
> support in favour of delayed allocation like is common on Linux, so
> on Windows it's a dead end technology and is officially on track for
> deprecation.
>
> I agree this doesn't help you hugely right now. I suspect that
> subclassing your own Boost.Iostreams adapter with the right sparse
> files functions is likely your best course of action. Sorry.
>
> Niall
>
> --
> Currently unemployed and looking for work.
> Work Portfolio: http://careers.stackoverflow.com/nialldouglas/
>
>
>
>
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