Re: please verify the code

websnarf@xxxxxxxxx wrote: 
Roman Mashak wrote:

I wrote function parsing the fully-quilified domain name and extracting
'host' and 'domain' parts seperately.



I am highly skeptical that the *functionality* of your code is correct.
 I usually take URLs to be of the form:
(<subdomainname>.)*<host-domainname>.<top-level-domainname> where
certain domain names have exceptional rules (co.uk, for example).
Ripping off the top most part usually just gets your some
sub-assignment by the host themselves.


[...] The important thing for me is to keep
original string (pointed by 'fqdn' in function). Is my way of coding
correct, is there a way to optimize function and make it not so clumsy (I
like the code produced by K&R in their famous book: brief, clear,
comprehensible, nothing superfluous :) ).



This newsgroup is poor place to come for "optimization" help, unless
you mean making it somehow look like K&R-style syntax or something like
that.  But I happen to see your post so ...

First of all, why do you do the extra copying step through p?  Its
unnecessary!  Presumably, you have two destination buffers ready to
receive data, just do your final manipulations in there:

----------------------------------------

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>

static int
parse_fqdn(char *fqdn, char *host, char *domain) {
	char *s = strstr (fqdn, ".");
	ptrdiff_t len = s - fqdn;

	if (NULL == s) return -1;
	memcpy (host, fqdn, len);
	host[len] = '\0';
	strcpy (domain, s + 1);
	return 0;
}

#define BUFLEN 1024

int main(void) {
    char dom[] = "www.my.example.dom.ain";
    static char h[BUFLEN], d[BUFLEN];

    if ( parse_fqdn(dom, h, d) == 0 )
        printf("fqdn='%s'\nhostname='%s', domain name='%s'\n", dom, h,
d);
    return EXIT_SUCCESS;
}

----------------------------------------

Ok, notice how I moved the BUFLEN definition below the parse_fqdn
definition?  In this way you can make somewhat more enlightened
decisions about the target buffer length in the future, if necessary.
For example, in your main you could easily do this:

    static char h[sizeof (dom)], d[sizeof (dom)];

and avoid the use of predefined fixed size buffers altogether.  In more
dynamic situations,  you would malloc char*'s with the strlen() of the
input strings or something to that effect.

Of course when you get tired of buffer overflows, performance problems,
and other buffer management issues, you can just use "The Better String
Library":

----------------------------------------

#include <stdlib.h>
#include <stdio.h>
#include "bstrlib.h"

int main(void) {
	struct tagbstring dom = bsStatic ("www.my.example.dom.ain");
	int i = bstrchr (&dom, '.'); /* I think bstrrchr is what you really
want here */
	if (BSTR_ERR != i) {
		bstring h = blk2bstr (dom.data, i);
		bstring d = blk2bstr (dom.data + i + 1, dom.slen - (i + 1));
		printf("fqdn='%s'\nhostname='%s', domain name='%s'\n",
			dom.data,
			bdatae (h, "<Out of memory>"),
			bdatae (d, "<Out of memory>"));
		bdestroy (h);
		bdestroy (d);
	}
	return EXIT_SUCCESS;
}

----------------------------------------

Notice how there is no "#include <string.h>" here?  As a good rule of
thumb -- there is a good chance you are introducing performance
problems if you have included that file.

Ok, I'll bite. How does "#include <string.h>" affect the performance of
anything that doesn't use it?

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
                    --- Albert Einstein ---
.

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