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

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

Johan Herland [off-list ref] wrote:

quoted

+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, [off-list ref]
www.herland.net