RE: [PATCH v4 04/12] btrace: Use function segment index in call iterator.

Metzger, Markus T
2017-05-11T10:02:42Z

Hello Tim,

> /* See btrace.h. */
> @@ -2702,26 +2684,14 @@ btrace_find_call_by_number (struct
> btrace_call_iterator *it,
> const struct btrace_thread_info *btinfo,
> unsigned int number)
> {
> - const struct btrace_function *bfun;
> + const unsigned int length = btinfo->functions.size ();
>
> - for (bfun = btinfo->end; bfun != NULL; bfun = bfun->flow.prev)
> - {
> - unsigned int bnum;
> -
> - bnum = bfun->number;
> - if (number == bnum)
> - {
> - it->btinfo = btinfo;
> - it->function = bfun;
> - return 1;
> - }
> -
> - /* Functions are ordered and numbered consecutively. We could bail out
> - earlier. On the other hand, it is very unlikely that we search for
> - a nonexistent function. */
> - }
> + if ((number == 0) || (number > length))
> + return 0;
>
> - return 0;
> + it->btinfo = btinfo;
> + it->index = number - 1;
> + return 1;
> }

We have those +1 and -1 operations throughout the code. Should we introduce
some small helpers to document what we're doing? E.g.

static inline unsigned int btrace_call_number_from_index (unsigned int call_index)
{
return call_index + 1;
}

and

static inline unsigned int btrace_call_number_to_index (unsigned int call_number)
{
return call_number - 1;
}

Regards,
Markus.

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