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From:	"Dave Korn" <dk AT artimi DOT com>
To:	<cygwin AT cygwin DOT com>
Subject:	RE: Problem with gzip
Date:	Wed, 14 Apr 2004 15:57:38 +0100
MIME-Version:	1.0
In-Reply-To:	<20040414143600.GB5982@coe.bosbc.com>
Message-ID:	<NUTMEGHDgWwGgDpPvOb0000046c@NUTMEG.CAM.ARTIMI.COM>
X-OriginalArrivalTime:	14 Apr 2004 14:57:38.0546 (UTC) FILETIME=[D419ED20:01C42230]

> -----Original Message-----
> From: cygwin-owner On Behalf Of Christopher Faylor
> Sent: 14 April 2004 15:36

> How about some *details* about how you made the suspect logs.tar.gz
> file.

  He made it by taking a valid .gz file and running it through u2d!  Or
perhaps some accident with textmode mountpoints.  Permit me to demonstrate
by turning all the CR/LF pairs back into plain LFs (although to be precise,
I should be referring to hex $0d and $0a bytes, since this file isn't an
ASCII file and those aren't actually CR and LF in the context of raw binary
data):

------->snip!<-------
dk AT mace /davek> unzip test.zip
Archive:  test.zip
   creating: test/
   creating: test/logs/
  inflating: test/logs/config.log
  inflating: test/logs/my_check.log
  inflating: test/logs/my_conf.log
 extracting: test/logs.tar.gz
dk AT mace /davek> cd test
dk AT mace /davek/test> ls -la
total 5
drwxr-xr-x+   3 dk       Domain U        0 Apr  6 11:40 .
drwx------+  30 dk       Domain U        0 Apr 14 15:52 ..
drwxr-xr-x+   2 dk       Domain U        0 Apr  6 11:22 logs
-rw-r--r--    1 dk       Domain U     4707 Apr  6 11:37 logs.tar.gz
dk AT mace /davek/test> mv logs old.logs
dk AT mace /davek/test> sed -e 's/\\r\\n/\\n/g' logs.tar.gz >logs-fixed.tar.gz
dk AT mace /davek/test> tar xfvz logs.tar.gz
logs/
logs/config.log
tar: Skipping to next header

gzip: stdin: invalid compressed data--crc error

gzip: stdin: invalid compressed data--length error
tar: Archive contains obsolescent base-64 headers
tar: Child returned status 1
tar: Error exit delayed from previous errors
dk AT mace /davek/test> tar xfvz logs-fixed.tar.gz
logs/
logs/config.log
logs/my_check.log
logs/my_conf.log
dk AT mace /davek/test> ls -la logs/
total 25
drwxr-xr-x+   2 dk       Domain U        0 Apr 14 15:53 .
drwxr-xr-x+   4 dk       Domain U        0 Apr 14 15:53 ..
-rw-r--r--    1 dk       Domain U     6872 Apr  6 11:21 config.log
-rw-r--r--    1 dk       Domain U    12183 Apr  6 11:21 my_check.log
-rw-r--r--    1 dk       Domain U     5314 Apr  6 11:21 my_conf.log
dk AT mace /davek/test>
------->snip!<-------

  Note that running d2u on the file won't fix it: d2u will delete all the
$0d bytes regardless of whether they're followed by $0a or not, which isn't
what we want; there's some genuine $0d's in there.

>  The above errors seem to indicate that gzip is correctly
> detecting a damaged .gz file.

  Absolutely so.  Every $0a byte got a bogus $0d prepended to it.  No wonder
it wouldn't unpack!


    cheers, 
      DaveK
-- 
Can't think of a witty .sigline today....


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