On Thu, Jun 01, 2017 at 02:47:48PM +0200, Jiri Slaby wrote:
> On 06/01/2017, 02:26 PM, Josh Poimboeuf wrote:
> > On Thu, Jun 01, 2017 at 01:05:39PM +0200, Peter Zijlstra wrote:
> >> On Thu, Jun 01, 2017 at 12:44:16AM -0500, Josh Poimboeuf wrote:
> >>
> >>> +static struct undwarf *__undwarf_lookup(struct undwarf *undwarf,
> >>> + unsigned int num, unsigned long ip)
> >>> +{
> >>> + struct undwarf *first = undwarf;
> >>> + struct undwarf *last = undwarf + num - 1;
> >>> + struct undwarf *mid;
> >>> + unsigned long u_ip;
> >>> +
> >>> + while (first <= last) {
> >>> + mid = first + ((last - first) / 2);
> >>> + u_ip = undwarf_ip(mid);
> >>> +
> >>> + if (ip >= u_ip) {
> >>> + if (ip < u_ip + mid->len)
> >>> + return mid;
> >>> + first = mid + 1;
> >>> + } else
> >>> + last = mid - 1;
> >>> + }
> >>> +
> >>> + return NULL;
> >>> +}
> >>
> >> That's a bog standard binary search thing, don't we have a helper for
> >> that someplace?
> >
> > I wasn't able to find one...
>
> There is bsearch, but that doesn't support searching for a value in
> between of 2 keys. I.e. what we typically have is these keys:
> some_function1 at 0x1000
> some_function2 at 0x2000
> and we look for IP which can be e.g. 0x1010. The bsearch's cmp function
> currently has no option to say, yes, the last one you asked me was the
> right one, this one is after it already.
Actually, I think bsearch would work with the latest version of the data
structure. It now has a len field, so we can do a self-contained
compare.
--
Josh
