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spec compliance: header CRC?

From: Greg Roelofs
Subject: spec compliance: header CRC?
Date: Wed, 23 Jun 2010 15:23:42 -0700

Hey folks,

>From what I can tell perusing the source code of various versions, GNU gzip
has never actually supported the documented purpose of flagbit 1, "FHCRC".
http://www.ietf.org/rfc/rfc1952.txt says "[The FHCRC bit was never set by
versions of gzip up to 1.2.4, even though it was documented with a different
meaning in gzip 1.2.4.]"  However, it appears that that same "different"
(and arguably pointless) meaning--i.e., "multi-part continuation"--continues
to be honored by all subsequent versions, including 1.4.0.

Are there any plans to address this?  Sun's JDK supports the header-CRC
interpretation, as does my own decompressor implementation in Hadoop.  The
whole concept of "multi-part" archives (as opposed to multi-member/concat-
enated files) was a stupid carryover from the PKZIP/floppy-disk days, so I
find it hard to believe it will ever be either desired or supported in gzip,
particularly since the 2GB limit was eliminated nearly a decade ago.  It
would be great if 1.5 supported the header CRC as specified.  (This isn't
really a backward-compatibility issue, either, insofar as no version of
gzip has ever done anything but bail when that bit is set.  Doing the Right
Thing with it would be, you know...novel. ;-) )

Oh, also please update the README as follows:

--- README.old  2010-01-03 09:26:02.000000000 -0800
+++ README      2010-06-23 15:20:18.000000000 -0700
@@ -119,9 +119,9 @@
 gzip and gunzip are distributed as a single program. zip and unzip
 are, for historical reasons, two separate programs, although the
-authors of these two programs work closely together in the info-zip
+authors of these two programs work closely together in the Info-ZIP
 team. zip and unzip are not associated with the GNU project.
-See http://www.cdrom.com/pub/infozip/ for more about zip and unzip.
+See http://www.info-zip.org/ for more about zip and unzip.

Greg Roelofs          address@hidden           http://pobox.com/~newt/
Newtware, PNG Group, AlphaWorld Map, Yahoo! Grid/Hadoop, ...

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