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

From: Linus Torvalds <torvalds@osdl.org>
Date: Jul 11, 2006, 18:58 UTC
Message-ID: <Pine.LNX.4.64.0607111153170.5623@g5.osdl.org>
In-Reply-To: <Pine.LNX.4.63.0607112031150.29667@wbgn013.biozentrum.uni-wuerzburg.de>

On Tue, 11 Jul 2006, Johannes Schindelin wrote:

> 
> Why not just say
> 
> 	return *hdr ? -1 : bytes;

Hey, whatever works. I rewrote more, and edited some of my changes down again..

> 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.

The problematic case is actually the other way around: my "parse_ascii_sha1_header()" isn't strict enough.

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).

Show 12 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.

Show 9 quoted lines

> >  int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
> >  {
> > -	int status;
> > +	int status, hdrlen;
> >  	unsigned long mapsize, size;
> >  	void *map;
> >  	z_stream stream;
> 
> This hunk is unnecessary, right?

Yeah, never mind. That function didn't actually need the hdrlen, it only cared about the SHA1.

		Linus