Re: SEEK_HOLE Support in Cygwin?

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Aug  7 10:33, Corinna Vinschen wrote:
> Wrong mailing list, use cygwin AT cygwin DOT com for user questions.
> 
> On Aug  6 19:14, Cedric Blancher wrote:
> > Good evening!
> > 
> > Are there plans for a SEEK_HOLE support to Cygwin, e.g. on top of the
> > FSCTL_QUERY_ALLOCATED_RANGES api (if appropriate)?
> 
> No plans, but patches are welcome.  This looks like a fun task for a
> rainy weekend.

Today was a really rainy day and I had to wait for a test system to
come up, so I hacked on SEEK_DATA/SEEK_HOLE support.

Check out the next Cygwin test release 3.5.0-0.384.g9939aa7d0945.

Note that this defaults to the default behaviour described in the
Linux man page, see https://man7.org/linux/man-pages/man2/lseek.2.html

I.e., "In the simplest implementation, a filesystem can support the
operations by making SEEK_HOLE always return the offset of the end of
the file, and making SEEK_DATA always return offset"

The real deal obviously requires a filesystem supporting sparse files,
*and* it requires that you access the file via a mount point with the
"sparse" option set!  The mount option "sparse" is not set by default.


Corinna