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Re: string to size_t

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Oğuz <oguzismailuysal@gmail.com> writes:

> I wrote the function below for converting a string to size_t without
> manually calculating its value digit by digit. It first converts the
> string to intmax_t, and if the conversion fails due to a range error
> and SIZE_MAX doesn't fit into an intmax_t, it tries again with
> uintmax_t. In both cases, if the result is less than zero it
> fails. And on success it populates *result with the result.
>
> It works on my machine and a couple others I tried, but I'm not sure
> if it's good C, or a good idea at all. What do you think about it?
>
> int
> strtosize(const char *nptr, char **endptr, int base, size_t *result) {

This name encroaches on the implementation's reserved name space.  Also,
I would consider mirroring the return value and semantics of the other
standard strtoXXX functions.  It's not a great interface to mimic, but
it is what readers are likely to expect.

> 	intmax_t s;
> 	uintmax_t u;
>
> 	errno = 0;
> 	s = strtoimax(nptr, endptr, base);
>
> 	if (errno == 0 && s >= 0 && s <= SIZE_MAX) {

This test may not do what you want.  When the string contains junk (for
example "#") s will be 0 and errno will not have been changed.

If this matters to you, you need to pass your own non-zero "end" pointer
to strtoimax and check that:

  char *ep;
  intmax_t s = strtoimax(nptr, &ep, base);

  if (errno == 0 && ep > nptr && s >= 0 && s <= SIZE_MAX) {
        *result = u;
        if (endptr) *endptr = ep;
	return 1;
  }

I'm late to the party so I'm only making these tangential remarks...

-- 
Ben.

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Thread

string to size_t Oğuz <oguzismailuysal@gmail.com> - 2022-12-19 14:15 +0300
  Re: string to size_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-19 09:59 -0800
    Re: string to size_t Oğuz <oguzismailuysal@gmail.com> - 2022-12-19 21:34 +0300
      Re: string to size_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-19 10:49 -0800
        Re: string to size_t Richard Damon <Richard@Damon-Family.org> - 2022-12-19 14:29 -0500
          Re: string to size_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-19 12:05 -0800
    Re: string to size_t scott@slp53.sl.home (Scott Lurndal) - 2022-12-19 18:40 +0000
      Re: string to size_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-19 12:07 -0800
        Re: string to size_t scott@slp53.sl.home (Scott Lurndal) - 2022-12-19 20:31 +0000
      Re: string to size_t Tony Oliver <guinness.tony@gmail.com> - 2022-12-19 16:33 -0800
    Re: string to size_t Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-19 11:20 -0800
  Re: string to size_t Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-19 22:16 +0000

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