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Date: Wed, 15 Feb 2012 10:33:52 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: File operations really slow in emacs
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On Feb 15 04:35, Mark Geisert wrote:
> Corinna Vinschen writes:
> > > > Does anybody know a system call which allows to fetch the network drive
> > > > state (connected/not connected) without a billion microsecond timeout?
> > > 
> > > I just looked into this and I really don't see a way.  While there's a
> > > NetUseGetInfo call, which is pretty fast even for unavailable drives,
> > > it's not reliable.  Even if the drive is available again, it can take
> > > minutes in which it still returns a status of "Session lost".  I'm not
> > > sure this is what we want.
> > 
> > ...and the call doesn't work for NFS drives.  Too bad.
> 
> Does WNetGetConnection() do any better?  It's referenced on the NetUseGetInfo()
> page in MSDN.  Claims to support other providers besides SMB.

Yes, that's right.  Alas, BTDT.  The function returns success even
if the share becomes unavailable.

> Apart from that, is "net use" the mount table Ryan was referring to?  Can we
> tell what it's doing to identify connected and disconnected drives?

Given it's import table it uses all functions available.  I see at
least these:

  NetUseEnum
  NetUseGetInfo
  WNetCloseEnum
  WNetEnumResourceW
  WNetOpenEnumW
  WNetGetConnectionW
  WNetGetLastErrorW
  WNetCancelConnection2W
  WNetAddConnection2W

But "net use" is not quite accurate either.  If you switch off a
remote share it recognizes the disconmnection pretty fast, but if
the share becomes available again, it stays in the disconnected state
for quite some time, just like the NetUseGetInfo function.

But, on second thought, maybe that's ok for us.  It would at least
help for SMB drives.  I'll look into that again at one point.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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