Re: calculating length of an substring

"brasilino@xxxxxxxxx" <brasilino@xxxxxxxxx> writes:

Hi Folks:

I'm trying to calculating a substring length directly from pointer
address, like this:

char *e = NULL, *s = NULL;
int len = 0;

s = strchr (url,'.');
e = strrchr (url,'?');
len = (int) s - e;

You wanted
len = (int)(s - e);
.. The way you have it, only s will be cast to an int; and you can't
subtract a pointer from an int!

The cast is completely superfluous, though; I'd recommend removing
it. If you like, you can first check that it will actually _fit_ into
an int (the type of the difference of pointers is ptrdiff_t, defined
in <stddef.h>. Or better yet, use a ptrdiff_t to store the result (if
that suits your needs otherwise).

A size_t actually makes the most sense for representing a string
length, though, at least to me.

--
Micah J. Cowan
Programmer, musician, typesetting enthusiast, gamer...
http://micah.cowan.name/
.

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