Creating Compressed Loop FS from stdin

[Peter Pentchev]

On Thu, Dec 30, 2004 at 03:32:27PM +0200, Maxim Sobolev wrote:
> Peter Pentchev wrote:
> >On Thu, Dec 30, 2004 at 01:28:28PM +0100, Matteo Riondato wrote:
> >
> >>Il giorno Gio, 30-12-2004 alle 12:34 +0200, Peter Pentchev ha scritto:
> >>
> >>>This could be fixed by the following patch.  I'm CC'ing Maxim Sobolev,
> >>>the author of mkuzip(8); Maxim, do you have any objections to this patch?
> >>
> >>Thank you for the answer and fo the patch! I hope Maxim will commit it
> >>soon.
> >
> >
> >Actually, if Maxim has no objections, I could commit it myself.
> >However, it would be totally understandable if he doesn't answer in
> >the next day or three, what with the calendar moving ahead and all :)
> 
> It will not help, since AFAIK you can't seek stdin anyway, or even if I 
> am wrong and you can seek it to the end you will be unable to seek it 
> backward.

I tested the patch before posting it, fully expecting to find that stdin
really cannot be seeked (sought? :), and surprisingly it worked, at least
on RELENG_5 as of today!

> I've already replied to this message, but Matteo has some very strange 
> settings of his smtp relay so that neither my original message nor my 
> follow-up in which I had forwarded mail delivery error message got through.
> 
> -Maxim
> 
> -------- Original Message --------
> Subject: Re: Creating Compressed Loop FS from stdin
> Date: Fri, 17 Dec 2004 17:14:48 +0200
> From: Maxim Sobolev <sobomax at portaone.com>
> Organization: Porta Software Ltd
> To: Matteo Riondato <rionda at freesbie.org>
> References: <1103290915.8516.9.camel at kaiser.sig11.org>
> 
> This is not going to work by design unfortunately. cloop format has
> serious design flaw: it contains variable-lengh header at the beginning
> of the compressed image, so that before doing compression mkuzip(1) uses
> stat(2) call at the original file to get its size and reserve necessary
> space, which doesn't work with /dev/stdin as you may guess. Original GNU
> utility either keeps the whole compressed image in memory or uses some
> form of temporary storage (I don't quite remember) to work around this
> problem.

Well, another solution would be to make mkuzip use a temporary file
(obviously, keeping the whole thing in memory would be a bad idea for
big ISO filesystems ;).  However, as I noted above, my lseek patch
works at least for RELENG_5.  Can somebody test it on -CURRENT?

G'luck,
Peter

-- 
Peter Pentchev	roam at ringlet.net    roam at cnsys.bg    roam at FreeBSD.org
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