/*-
 * Compact mkstemp(3)-only implementation, for klibc
 *
 * Copyright (c) 2009
 *	Thorsten Glaser <tg at mirbsd.de>
 *
 * This file is available under the same terms ("historic
 * permission clause") as klibc itself or under the terms
 * of The MirOS Licence (dual licenced).
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
mkstemp(char *template)
{
	unsigned int i;
	char *cp, *sp;
	struct stat sbuf;

	cp = template;
	while (*cp)
		++cp;
	--cp;

	if (cp < template) {
		errno = EINVAL;
		return (-1);
	}

	/* generate random suffix */
	while (cp > template && *cp == 'X') {
		i = arc4random(); i = i % (26 + 26);
		*cp-- = i < 26 ? 'A' + i : 'a' + i - 26;
	}
	sp = cp + 1;

	/* check the target directory */
	while (cp > template && *cp != '/')
		--cp;
	if (cp > template) {
		*cp = '\0';
		i = stat(template, &sbuf);
		*cp = '/';

		if (i != 0)
			/* stat failed, pass errno */
			return (-1);
		if (!S_ISDIR(sbuf.st_mode)) {
			errno = ENOTDIR;
			return (-1);
		}
	}

	cp = sp;
	for (;;) {
		if ((i = open(template, O_CREAT|O_EXCL|O_RDWR, 0600)) >= 0 ||
		    errno != EEXIST)
			break;

		while (*cp == 'Z')
			if (!*++cp)
				return (-1);
		if (*cp == 'z')
			*cp = 'A';
		else
			++*cp;
	}
	return (i);
}