[delphizip] Re: Exclusive file access
- From: "Russell Peters" <russellpeters@xxxxxxxxxxx>
- To: <delphizip@xxxxxxxxxxxxx>
- Date: Wed, 25 Sep 2002 15:27:50 +1000
Sorry, I think it might be a little hard for you to test zipdll 1.7.0.5
yet - I cannot find it on my site!
Will compress and post it tonight
Russell Peters
http://www.users.bigpond.com/russellpeters/delphizip.html
----- Original Message -----
From: "Russell Peters" <russellpeters@xxxxxxxxxxx>
To: <delphizip@xxxxxxxxxxxxx>
Sent: Wednesday, September 25, 2002 7:40 AM
Subject: [delphizip] Re: Exclusive file access
>
> Unfortunately the dlls don't use the windows API (use older but standard C
> routines ie fopen, fread etc).
> As soon as I can I will have a look at (optionally) forcing the dll to
make
> a temporary file.
> Actually I thought I did make it do so (in 1.7.0.5) if the target was not
> FIXED_DISK, FLOOPY_DISK or RAM_DISK making it only in danger of multiple
> access while being transferred to final destination and I would be very
> surprised if it allowed any shared writes.
> Russell Peters
> http://www.users.bigpond.com/russellpeters/delphizip.html
>
>
> ----- Original Message -----
> From: "James Turner" <james.d.h.turner@xxxxxxxxxxxx>
> To: <delphizip@xxxxxxxxxxxxx>
> Sent: Wednesday, September 25, 2002 12:07 AM
> Subject: [delphizip] Re: Exclusive file access
>
>
> >
> > I haven't tried what I'm about to suggest but I can think of no reason
why
> > there should be a problem.
> >
> > To prevent write access to zip file simple open it with FILE_SHARE_READ
> > access. This will prevent others from writing to the file. Before
calling
> > the ZipMaster.Add function, you must call CloseHandle. When the
> > ZipMaster.Add function has completed, reopen the file with
FILE_SHARE_READ
> > access.
> >
> > If the ZipDLL allows shared write access (something I doubt) there could
> be
> > problems.
> >
> > See Microsoft documentation on the API function CreateFile for more
> details.
> >
> > This is not a perfect solution, but in practice should be ok. You should
> > also consider monitoring the file date - this is the approach I use to
> solve
> > a slightly different problem.
> >
> > James Turner
> >
> > PS
> > I have a feeling that it is possible to limit the instances of file
> sharing
> > under NT. This might be a better solution. The function LockFileEx may
> also
> > be useful.
> >
> > ----- Original Message -----
> > From: "Petko Kafedjiski" <kafedjiski@xxxxxxxxxxx>
> > To: <delphizip@xxxxxxxxxxxxx>
> > Sent: Tuesday, September 24, 2002 11:00 AM
> > Subject: [delphizip] Re: Exclusive file access
> >
> >
> > >
> > > Thank you very much Russell.
> > >
> > > I missed one thing: by doing, what you advice (iterating through all
> > > instances), I suspect that other instances run on other machines on
the
> > > network can also overwrite the file, am I right?
> > >
> > > However, I have an idea and it is to create a temp file for every
> instance
> > > that opens the archive, so this will fix the problem to a given level.
> > >
> > > Regards,
> > > Petko Kafedjiski
> > > Milenix Software Ltd.
> > > http://www.milenix.com
> > >
> > > P.S.: I am sorry for my bad english :)
> > >
> > > ----- Original Message -----
> > > From: "Russell Peters" <russellpeters@xxxxxxxxxxx>
> > > To: <delphizip@xxxxxxxxxxxxx>
> > > Sent: Monday, September 23, 2002 11:58 PM
> > > Subject: [delphizip] Re: Exclusive file access
> > >
> > >
> > > >
> > > > This would be helped if I can add an AddTemp option (force
add/modify
> to
> > a
> > > > temporary file), other than that the only way that comes to mind is
to
> > > make
> > > > a temporary file (for each instance) to work on.
> > > > - Russell Peters
> > > > A late thought - it should be possible to iterate through all
> instances
> > > > checking ZipBusy and only writing if none busy.
> > > > Hope this helps.
> > > > ----- Original Message -----
> > > > From: "Petko Kafedjiski" <kafedjiski@xxxxxxxxxxx>
> > > > To: <delphizip@xxxxxxxxxxxxx>
> > > > Sent: Tuesday, September 24, 2002 4:15 AM
> > > > Subject: [delphizip] Exclusive file access
> > > >
> > > >
> > > > >
> > > > > Hello to all! I am new to this mail list, so my question may be
> > answered
> > > > > already and I want to appologize, if it is so.
> > > > >
> > > > > I have an application (http://www.milenix.com - MyInfo 2), which
> uses
> > > > BCBZip
> > > > > ver. 1.6. However there is a problem, because a single file could
be
> > > > opened
> > > > > in two instances of the program and then when the user saves the
> file
> > > > (which
> > > > > is actually an archive with many files within) in one of the
> instances
> > > and
> > > > > then saves it in the other - there is a mess with the file and
> > sometimes
> > > > > even the all information could be lost.
> > > > >
> > > > > I want to prevent this by gaining exclusive read-write access of
the
> > > file,
> > > > > so it could be opened only once. There is no such option in
BCBZip,
> > but
> > > is
> > > > > there some way to workaround it?
> > > > >
> > > > > Thank you very much for your time!
> > > > > Petko Kafedjiski
> > > > > Milenix Software Ltd.
> > > > > http://www.milenix.com
> > > > >
> > > > >
> > > >
> > >
> >
> >
> >
>
>
>
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