GNU bug report logs - #49721
NAME flag incorrectly set

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Lee Shallis <gb2985 <at> gmail.com>
To: bug-gzip <at> gnu.org
Subject: NAME flag incorrectly set
Date: Sat, 24 Jul 2021 11:14:25 +0100

I've been following a guide on the deflate algorithm (because I wanted
one where I could control how memory is allocated just as Lua allows)
and found when I put this:

echo "hello hello hello hello" | gzip

into the terminal gzip incorrectly set the NAME flag, it was only
after editing it out I was able to deflate the resulting file, the
same applies for this:

echo -n "abaabbbabaababbaababaaaabaaabbbbbaa" | gzip

Both of which are the examples given on
https://blog.za3k.com/understanding-gzip-2/

Message #8 received at 49721 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: gb2985 <at> gmail.com
Cc: 49721 <at> debbugs.gnu.org
Subject: Re: bug#49721: NAME flag incorrectly set
Date: Sat, 24 Jul 2021 12:32:23 -0700

On 7/24/21 3:14 AM, Lee Shallis wrote:
> when I put this:
> 
> echo "hello hello hello hello" | gzip
> 
> into the terminal gzip incorrectly set the NAME flag

I suppose you're talking about the FNAME flag described by RFC 1952? I 
don't observe any problem with gzip 1.10:

$ echo "hello hello hello hello" | gzip | od -t x1
0000000 1f 8b 08 00 00 00 00 00 00 03 cb 48 cd c9 c9 57
0000020 c8 40 27 b9 00 00 88 59 0b 18 00 00 00
0000035

The FLG byte is 00, which means FNAME is not set.

Message #13 received at 49721-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: gb2985 <at> gmail.com
Cc: 49721-done <at> debbugs.gnu.org
Subject: Re: bug#49721: NAME flag incorrectly set
Date: Sun, 25 Jul 2021 08:29:32 -0700

On 7/25/21 8:24 AM, Lee Shallis wrote:
> I just noticed my misunderstanding, seems because I forgot to read the
> compression byte as a compression byte, it got read as the flags byte,
> so I was off by a byte when reading the flags without realising.

Thanks for following up. Closing the bug report.

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