Re: [Qemu-devel] [PATCH] Better .dmg autodetection

[Alex Beregszaszi <alex@fsn.hu>]

Hi,

> > There are quiet lot fake dmg files floating around. These are just
> > raw images containing the Apple partition map and HFS partitions.
> 
> Those are not fake dmg.
> With Apple disk utility, you are free to choose if the dmg is to be
> compressed or not.
> Then, uncompressed dmg are valid ones.
> But, you don't need to manage them in block-dmg,c as those are just
> raw images...

I spoke about better _autodetection_. Right now if it finds the .dmg
extension, the file will be threaten as DMG, and it will fail if I throw
an uncompressed one at it.

> > * last check if the filename ends in .dmg
> 
> It seems to me that this check is not to be done.
> There's no need to. If the first sector (after decompression, if
> needed) is a valid Apple partition map _or_ a valid partition entry
> (ie with PM magic at start), then it's a valid dmg. File extensions
> never mean anything, they are just a user-interface oriented
> remainder, imho.

Dont forget that the current implementations relies only on the file
extension...

Wrong, if it starts with ER (disk header) or PM, it is definitely an
uncompressed file, thus it should be used via the raw interface. But if
the first bytes resemble the zlib compression, it is definitely a dmg
file which should be handled inside block-dmg.

-- 
Alex Beregszaszi 			e-mail: alex@fsn.hu
Free Software Network			cell: +36 70 3144424