RE: [cgmo-webcgm] Z compression research

["Galt, Stuart A" <stuart.a.galt@boeing.com>]

Section 2.3.1 of the RFC talks about the file structure.  The header block start
off with:

         ID1 (IDentification 1)
         ID2 (IDentification 2)
            These have the fixed values ID1 = 31 (0x1f, \037), ID2 = 139
            (0x8b, \213), to identify the file as being in gzip format.

They don't call it a magic number but it looks like something that
can be used to identify it as a gzip format file.

--
Stuart Galt
SGML Resource Group
stuart.a.galt@boeing.com
(206) 544-3656

 

> -----Original Message-----
> From: Cruikshank, David W 
> Sent: Thursday, September 20, 2007 6:56 AM
> To: DULUC, Franck; Don Larson; CGM Open WebCGM TC
> Subject: RE: [cgmo-webcgm] Z compression research
> 
> I guess I also raises the question of if you find the "magic 
> number" for zcompress how do you know it's not an svgz file 
> instead of a cgmz file?
> 
> Thx...Dave
> 
> 
> Technical Fellow - Graphics/Digital Data Interchange Boeing 
> Commercial Airplane 206.544.3560, fax 206.662.3734 
> david.w.cruikshank@boeing.com
> 
> -----Original Message-----
> From: DULUC, Franck [mailto:franck.duluc@airbus.com]
> Sent: Thursday, September 20, 2007 6:31 AM
> To: Don Larson; CGM Open WebCGM TC
> Subject: RE: [cgmo-webcgm] Z compression research
> 
> i think it is the same for VRML.
> 
> Franck
> 
> -----Message d'origine-----
> De : Don Larson [mailto:dlarson@cgmlarson.com] Envoyé : 
> mercredi 19 septembre 2007 23:07 À : CGM Open WebCGM TC Objet 
> : [cgmo-webcgm] Z compression research
> 
> 
> All,
> 
> After researching Z compression, I have determined that the 
> file format used for compressed SVG is the same used by 
> "gzip" an open source software. And that there indeed is a 
> magic number in first 2 bytes indicating Z compression.
> 
> The complete specification for the gzip file format can found here:
> http://www.ietf.org/rfc/rfc1952.txt
> 
> Further details on gzip and source code can be found at:
> http://www.gzip.org/
> 
> 
> Regards,
> Don Larson
> 
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