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

["Metzger, Markus T" <markus dot t dot metzger at intel dot com>]

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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