Re: [PATCH 1/2] lib/strtox: introduce kstrtoull_suffix() helper

[Qu Wenruo]

On 2023/12/20 19:01, David Laight wrote:
> From: Qu Wenruo
> > Sent: 19 December 2023 21:18
> ...
> > > How about:
> > > 	suffix = *endptr;
> > > 	if (!strchr(suffixes, suffix))
> > > 		return -ENIVAL;
> > > 	shift = strcspn("KkMmGgTtPp", suffix)/2 * 10 + 10;
> >
> > This means the caller has to provide the suffix string in this
> > particular order.
>
> No, The strchr() checks that the suffix is one the caller wanted.
> The strcspn() is against a fixed list - so the order can be
> selected to make the code shorter.

Ah, got it.
Although in that case, the 1st parameter should be ("KkMmGgTtPpEe"), as
we still support "Ee", just not by default.

Thanks,
Qu
> Actually strcspn() isn't the function you need.
> There might be a function like strchr() that returns a count
> but I can't remember its name and it may not be in kernel.
> You might have to write:
> 	shift = 0;
> 	for (const char *sfp = "KkMmGgTtPp"; suffix != *sfp; sfp++, shift++) {
> 		if (!*sfp)
> 			return -EINVAL;
> 	}
> 	shift = shift/2 + 1 * 10;
>
> 	David
>
> -
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