Re: [RFC/PATCHv10 01/11] fast-import: Proper notes tree manipulation

From: Johan Herland <johan@herland.net>
Date: Dec 8, 2009, 01:55 UTC
Message-ID: <200912080255.17568.johan@herland.net>
In-Reply-To: <20091207164311.GE17173@spearce.org>

On Monday 07 December 2009, Shawn O. Pearce wrote:

Show 18 quoted lines

> Johan Herland <johan@herland.net> wrote:
> > +static unsigned char convert_num_notes_to_fanout(uintmax_t num_notes)
> > +{
> > +	unsigned char fanout = 0;
> > +	while ((num_notes >>= 8))
> > +		fanout++;
> > +	return fanout;
> > +}
> > +
> > +static void construct_path_with_fanout(const char *hex_sha1,
> > +		unsigned char fanout, char *path)
> > +{
> > +	unsigned int i = 0, j = 0;
> > +	if (fanout >= 20)
> > +		die("Too large fanout (%u)", fanout);
> 
> Shouldn't convert_num_notes_to_fanout have a guard to prevent this
> case from happening?

Well, it sort of already does (unless uintmax_t is more than 19 * 8 = 152 bits wide... ;)

Not sure what you're getting at:

- Should I add a "&& fanout < 19" condition to the while loop in 
convert_num_notes_to_fanout()?

- Should I remove the "if (fanout >= 20) die(...)"? Of course, 
construct_path_with_fanout() is only supposed to be called with values 
returned from convert_num_notes_to_fanout(), so the condition only tests a 
precondition that we believe to be true (FTR, it was converted from an 
equivalent assert() in an earlier iteration), but I normally test for these 
things anyway (when they are not blindingly obvious), just to make sure... 
(and I believe a die(...) is kinder to the user than a segfault...)

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net