Re: New versions of openbsd_{basename,dirname}.c

[Svante Signell <svante.signell@telia.com>]

On Tue, 2012-01-17 at 11:05 +0100, Samuel Thibault wrote:
> Svante Signell, le Tue 17 Jan 2012 10:52:47 +0100, a écrit :

New version of openbsd_basename_new.c attached.

> In addition to that, it might be better for performance to rather
> remember how much memory was previously allocated, and only reallocate
> if more memory is needed, and twice as much, so as to reduce the amount
> of free/malloc calls.

I don't think this kind of optimization is needed for the libtar
application. It definitely complicates the code.

valgrind output below (./test_base+dirname):
==14515== 
==14515== HEAP SUMMARY:
==14515==     in use at exit: 4 bytes in 2 blocks
==14515==   total heap usage: 8 allocs, 6 frees, 49 bytes allocated
==14515== 
==14515== LEAK SUMMARY:
==14515==    definitely lost: 0 bytes in 0 blocks
==14515==    indirectly lost: 0 bytes in 0 blocks
==14515==      possibly lost: 0 bytes in 0 blocks
==14515==    still reachable: 4 bytes in 2 blocks
==14515==         suppressed: 0 bytes in 0 blocks
==14515== Rerun with --leak-check=full to see details of leaked memory
==14515== 
==14515== For counts of detected and suppressed errors, rerun with: -v
==14515== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 4 from 4)

/*	$OpenBSD: basename.c,v 1.4 1999/05/30 17:10:30 espie Exp $	*/

/*
 * Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef lint
static char rcsid[] = "$OpenBSD: basename.c,v 1.4 1999/05/30 17:10:30 espie Exp $";
#endif /* not lint */

#include <errno.h>
#include <string.h>
#include <sys/param.h>
#include <stdlib.h>

char *
openbsd_basename_new(path)
	const char *path;
{
	static char *bname = NULL;
	register const char *endp, *startp;
	int len = 0;

	if (bname != NULL)
		free(bname);

	/* Empty or NULL string gets treated as "." */
	if (path == NULL || *path == '\0') {
		bname = strdup(".");
		return(bname);
	}

	/* Strip trailing slashes */
	endp = path + len - 1;
	while (endp > path && *endp == '/')
		endp--;

	/* All slashes becomes "/" */
	if (endp == path && *endp == '/') {
		bname = strdup("/");
		return(bname);
	}

	/* Find the start of the base */
	startp = endp;
	while (startp > path && *(startp - 1) != '/')
		startp--;

	len = endp - startp + 1;
	bname = malloc(len + 1);
	(void)strncpy(bname, startp, len);
	bname[len] = '\0';
	return(bname);
}