[Vm-dev] ImageFormat updates

[David T. Lewis]

Hi Subbu,

On Sun, Apr 30, 2017 at 10:26:18PM +0530, K K Subbu wrote:
>  
> Hi,
> 
> Is there an Inbox to upload patches to VMMaker for review?

That's probably a good idea, although posting to the vm-dev list as you
are doing here is fine for ImageFormat.

> 
> I generated a small fix to ImageFormat to generate magic pattern checks 
> at offset 512 also. I think some old Etoys images use this offset with a 
> launch script stuffed in the first 512 bytes. Is this deprecated now?

The 512 byte offset is a trick for letting the image file work as a
shell script, using a shebang line to run the image. I don't think it
gets used very often, but hopefully it still works, and that is the reason
for the offset check.

I don't know if it shsould go into the magic file entries, because when
set up in this manner it actually would be an executeble script. I guess
you could look at it either way though, either as a shell script or as
a Smalltalk image file.

> 
> I also feel 'unix' should be dropped from the method's name. file(1) 
> utility originated in Unix but is related to file contents and not to 
> kernel. It should be available for Mac/Win too.

As far as I know it is a unix utility. It would certainly be available
on OS X (which is a unix), though I'm not sure of its status on Windows.

> 
> I have also attached the resulting magic file and a workspace script to 
> generate a bunch of test header files to test the magic file. e.g.
> 
>  $ file -m magic *.image
> 
> Regards .. Subbu
> 

Thanks! I'll take a look at it.

Dave