tar/src/names.c

/* Look up user and/or group names.
   Copyright (C) 1988, 1992 Free Software Foundation

This file is part of GNU Tar.

GNU Tar is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Tar is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Tar; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*
 * Look up user and/or group names.
 *
 * This file should be modified for non-unix systems to do something
 * reasonable.
 */ 

#include <sys/types.h>
#include "tar.h"
#include "port.h"

#ifndef NONAMES
/* Whole module goes away if NONAMES defined.  Otherwise... */
#include <stdio.h>
#include <pwd.h>
#include <grp.h>

static int	saveuid = -993;
static char	saveuname[TUNMLEN];
static int	my_uid = -993;

static int	savegid = -993;
static char	savegname[TGNMLEN];
static int	my_gid = -993;

#define myuid	( my_uid < 0? (my_uid = getuid()): my_uid )
#define	mygid	( my_gid < 0? (my_gid = getgid()): my_gid )

/*
 * Look up a user or group name from a uid/gid, maintaining a cache.
 * FIXME, for now it's a one-entry cache.
 * FIXME2, the "-993" is to reduce the chance of a hit on the first lookup.
 *
 * This is ifdef'd because on Suns, it drags in about 38K of "yellow
 * pages" code, roughly doubling the program size.  Thanks guys.
 */
void
finduname(uname, uid)
	char	uname[TUNMLEN];
	int	uid;
{
	struct passwd	*pw;
	extern struct passwd *getpwuid ();

	if (uid != saveuid) {
		saveuid = uid;
		saveuname[0] = '\0';
		pw = getpwuid(uid); 
		if (pw) 
			strncpy(saveuname, pw->pw_name, TUNMLEN);
	}
	strncpy(uname, saveuname, TUNMLEN);
}

int
finduid(uname)
	char	uname[TUNMLEN];
{
	struct passwd	*pw;
	extern struct passwd *getpwnam();

	if (uname[0] != saveuname[0]	/* Quick test w/o proc call */
	    || 0!=strncmp(uname, saveuname, TUNMLEN)) {
		strncpy(saveuname, uname, TUNMLEN);
		pw = getpwnam(uname); 
		if (pw) {
			saveuid = pw->pw_uid;
		} else {
			saveuid = myuid;
		}
	}
	return saveuid;
}


void
findgname(gname, gid)
	char	gname[TGNMLEN];
	int	gid;
{
	struct group	*gr;
	extern struct group *getgrgid ();

	if (gid != savegid) {
		savegid = gid;
		savegname[0] = '\0';
		(void)setgrent();
		gr = getgrgid(gid); 
		if (gr) 
			strncpy(savegname, gr->gr_name, TGNMLEN);
	}
	(void) strncpy(gname, savegname, TGNMLEN);
}


int
findgid(gname)
	char	gname[TUNMLEN];
{
	struct group	*gr;
	extern struct group *getgrnam();

	if (gname[0] != savegname[0]	/* Quick test w/o proc call */
	    || 0!=strncmp(gname, savegname, TUNMLEN)) {
		strncpy(savegname, gname, TUNMLEN);
		gr = getgrnam(gname); 
		if (gr) {
			savegid = gr->gr_gid;
		} else {
			savegid = mygid;
		}
	}
	return savegid;
}
#endif