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Bug#494169: marked as forwarded (libarchive-dev: Please add a way to pre

Subject: Bug#494169: marked as forwarded libarchive-dev: Please add a way to precompute (non-compressed) archive size
From: Debian Bug Tracking System
Date: Fri, 08 Aug 2008 02:33:06 +0000
Your message dated Thu, 7 Aug 2008 21:31:27 -0500
with message-id <[email protected]>
has caused the   report #494169,
regarding libarchive-dev: Please add a way to precompute (non-compressed) 
archive size
to be marked as having been forwarded to the upstream software
author(s) [email protected]

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-- 
494169: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=494169
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Subject: FW: Bug#494169: libarchive-dev: Please add a way to precompute (non-compressed) archive size
From: John Goerzen
Date: Thu, 7 Aug 2008 21:31:27 -0500
Hi Tim,

We received the below feature request at Debian.  Not sure if it is
something you would be interested in implementing, but thought I'd
pass it along.

-- John

----- Forwarded message from Thibaut VARENE <[email protected]> -----

From: Thibaut VARENE <[email protected]>
Date: Thu, 07 Aug 2008 17:37:10 +0200
Reply-To: Thibaut VARENE <[email protected]>, [email protected]
To: Debian Bug Tracking System <[email protected]>
Subject: Bug#494169: libarchive-dev: Please add a way to precompute
        (non-compressed) archive size

Package: libarchive-dev
Severity: wishlist

Hi,

I thought I already reported this, but apparently I didn't so here's the 
idea: I'm the author of mod_musicindex, in which I use libarchive to 
send on-the-fly tar archives to remote clients.

Right now, the remote client's browser cannot display any ETA /  
%complete for the current download since I cannot tell before hand what 
will be the exact size of the archive I'm sending them.

It would be very nice if there were some API allowing for the 
precomputation of the final size of a non-compressed archive that would 
allow me to do something like:

archive_size = archive_size_header(a);
for (<filename in file list>) {
        archive_size += archive_size_addfile(filename);
        /* or using stat() and eg archive_size_addstat() */
}
archive_size += archive_size_footer(a);

(brainfart pseudo code, I hope you get the idea)

so that in the end archive_size will be exactly the size of the output 
archive (header/padding included), without having to actually read files 
or write the archive itself.

I could thus send the remote client the actual size of the data they're 
going to be send beforehand.

The trick is, this size cannot be approximate: the browser will cut the 
transfer even if I'm still sending them data if it has received as many
bits as it was told.

I'm under the impression that since this is about non-compressed 
archive, and considering the structure of a tar archive, my goal should 
be feasible without even having to read any input file. Am I wrong?

Hope I'm quite clear, thanks for your help

T-Bone

-- System Information:
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Kernel: Linux 2.6.22.14 (SMP w/4 CPU cores)
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----- End forwarded message -----

-- 
John Goerzen
Author, Foundations of Python Network Programming
http://www.amazon.com/exec/obidos/tg/detail/-/1590593715


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