Re: [PATCH 2/3] sha1_file: add the ability to parse objects in "pack file format"

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Jul 11, 2006, 19:20 UTC
Message-ID: <Pine.LNX.4.63.0607112116270.29667@wbgn013.biozentrum.uni-wuerzburg.de>
In-Reply-To: <Pine.LNX.4.64.0607111153170.5623@g5.osdl.org>

Hi,

On Tue, 11 Jul 2006, Linus Torvalds wrote:

Show 8 quoted lines

> On Tue, 11 Jul 2006, Johannes Schindelin wrote:
> 
> > You might want to add a comment saying "since the type is lowercase in 
> > ascii format, object_type must be 6 or 7, which is an invalid object 
> > type." It took me a little to figure that out...
> 
> It's not even correct in my version - I check the ASCII header _first_, so 
> by the time it looks at the binary one, it already knows it's not ascii.

Just realized it all by myself...

> Or, more likely, the parse_sha1_header() function should just be changed 
> to check the binary format first (and then add your comment about why that 
> is safe).

Yes, exactly.

Show 15 quoted lines

> > > +	bits = 4;
> > > +	while (!(c & 0x80)) {
> > > +		if (bits >= 8*sizeof(unsigned long))
> > > +			return -1;
> > > +		c = *hdr++;
> > > +		size += (unsigned long) (c & 0x7f) << bits;
> > > +		bytes++;
> > > +		bits += 7;
> > > +	}
> > 
> > Are you not losing the last byte by putting the "while" _before_ instead 
> > of _after_ the loop?
> 
> No. The very first byte can have the 0x80 end marker, when the size was 
> between 0..15.

Yes, I understand now. I was a little confused by the way it is written...

Thanks for the clarification, Dscho