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Re: K&R2, exercise 5-4, strend(s,t)

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Mark Bluemel <mark_bluemel@pobox.com> writes:
> /* return 1 if str2 occurs at the end of str1, zero otherwise */

This is pretty much what I'd do too, with a few tweaks.

>   int strend(const char* str1, const char* str2)
>    {
>      int str1_len;
>      int str2_len;

size_t is better.

>      const char *comparison_start;
> 
>      if ((str1 == NULL) || (str2 == NULL)) {
>        return 0;
>      }
> 
>      str1_len = strlen(str1);
>      str2_len = strlen(str2);
> 
>      if (str2_len  == 0) {
>        return 0;

Doesn't the empty string appear at the end of every string? Or did you mean
str1_len?

Either way, the calculation of the length you've not used yet can be 
delayed until this point, so that some trivial cases can be handled 
more quickly.

>      }
> 
>      if (str2_len > str1_len) {

If you calculate str1_len first, then you can use a strnlen[*] rather than
strlen on str2, in order to be able to bail early on the above condition.

>        return 0;
>      }
> 
>      comparison_start = str1 + str1_len - str2_len;
>      return !strcmp(comparison_start,str2);

Memcmp doesn't need to keep checking for '\0' characters, which you know
will be absent in the sections you're interested in comparing.

>    }

Phil

[* GNU provides one for you, but you might need to write your own,
it's a strlen with a maximum length.]

-- 
"At least you know where you are with Microsoft."
"True. I just wish I'd brought a paddle." -- Matthew Vernon

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Thread

K&R2, exercise 5-4, strend(s,t) arnuld <sunrise@invalid.address> - 2011-06-23 10:56 +0000
  Re: K&R2, exercise 5-4, strend(s,t) Ian Collins <ian-news@hotmail.com> - 2011-06-23 23:03 +1200
  Re: K&R2, exercise 5-4, strend(s,t) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-06-23 13:28 +0100
  Re: K&R2, exercise 5-4, strend(s,t) Mark Bluemel <mark_bluemel@pobox.com> - 2011-06-23 14:08 +0100
    Re: K&R2, exercise 5-4, strend(s,t) Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-06-24 02:22 +0300
      Re: K&R2, exercise 5-4, strend(s,t) Gene <gene.ressler@gmail.com> - 2011-06-23 18:14 -0700
        Re: K&R2, exercise 5-4, strend(s,t) Ike Naar <ike@sverige.freeshell.org> - 2011-06-24 06:18 +0000
          Re: K&R2, exercise 5-4, strend(s,t) Ike Naar <ike@sverige.freeshell.org> - 2011-06-24 06:58 +0000
    Re: K&R2, exercise 5-4, strend(s,t) Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-25 10:07 -0700
      Re: K&R2, exercise 5-4, strend(s,t) arnuld <sunrise@invalid.address> - 2011-06-27 08:02 +0000
        Re: K&R2, exercise 5-4, strend(s,t) Mark Bluemel <mark_bluemel@pobox.com> - 2011-06-27 10:13 +0100
        Re: K&R2, exercise 5-4, strend(s,t) Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-27 11:54 -0700
      Re: K&R2, exercise 5-4, strend(s,t) Mark Bluemel <mark_bluemel@pobox.com> - 2011-06-27 09:07 +0100
        Re: K&R2, exercise 5-4, strend(s,t) Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-27 11:51 -0700
          Re: K&R2, exercise 5-4, strend(s,t) Mark Bluemel <mark_bluemel@pobox.com> - 2011-06-28 08:19 +0100
            Re: K&R2, exercise 5-4, strend(s,t) Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-28 16:03 -0700

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