/* $OpenBSD: username.c,v 1.11 2003/06/15 16:24:44 millert Exp $	 */

/*
 *  Top users/processes display for Unix
 *  Version 3
 *
 * Copyright (c) 1984, 1989, William LeFebvre, Rice University
 * Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 OR HIS EMPLOYER 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.
 */

/*
 *  Username translation code for top.
 *
 *  These routines handle uid to username mapping.
 *  They use a hashing table scheme to reduce reading overhead.
 *  For the time being, these are very straightforward hashing routines.
 *  Maybe someday I'll put in something better.  But with the advent of
 *  "random access" password files, it might not be worth the effort.
 *
 *  Changes to these have been provided by John Gilmore (gnu@toad.com).
 *
 *  The hash has been simplified in this release, to avoid the
 *  table overflow problems of previous releases.  If the value
 *  at the initial hash location is not right, it is replaced
 *  by the right value.  Collisions will cause us to call getpw*
 *  but hey, this is a cache, not the Library of Congress.
 *  This makes the table size independent of the passwd file size.
 */

#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <pwd.h>

#include "top.local.h"
#include "utils.h"

struct hash_el {
	uid_t	uid;
	char	name[9];
};

static int      enter_user(uid_t, char *, int);
static int      get_user(uid_t);

#define	is_empty_hash(x)	(hash_table[x].name[0] == 0)

/* simple minded hashing function */
/*
 * Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
 * the hash_table.  Applied abs() function to fix. 2/16/96 tpugh
 */
#define	hashit(i)	(abs(i) % Table_size)

/* K&R requires that statically declared tables be initialized to zero. */
/* We depend on that for hash_table and YOUR compiler had BETTER do it! */
struct hash_el  hash_table[Table_size];

char *
username(uid_t uid)
{
	int hashindex;

	hashindex = hashit(uid);
	if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid)) {
		/* not here or not right -- get it out of passwd */
		hashindex = get_user(uid);
	}
	return (hash_table[hashindex].name);
}

uid_t
userid(char *username)
{
	struct passwd *pwd;

	/*
	 * Eventually we want this to enter everything in the hash table, but
	 * for now we just do it simply and remember just the result.
	 */
	if ((pwd = getpwnam(username)) == NULL)
		return ((uid_t)-1);

	/* enter the result in the hash table */
	enter_user(pwd->pw_uid, username, 1);

	/* return our result */
	return (pwd->pw_uid);
}

/*
 * wecare: 1 = enter it always, 0 = nice to have
 */
static int
enter_user(uid_t uid, char *name, int wecare)
{
	int hashindex;

#ifdef DEBUG
	fprintf(stderr, "enter_hash(%u, %s, %d)\n", uid, name, wecare);
#endif

	hashindex = hashit(uid);

	if (!is_empty_hash(hashindex)) {
		if (!wecare)
			return 0;	/* Don't clobber a slot for trash */
		if (hash_table[hashindex].uid == uid)
			return (hashindex);	/* Fortuitous find */
	}
	/* empty or wrong slot -- fill it with new value */
	hash_table[hashindex].uid = uid;
	(void) strlcpy(hash_table[hashindex].name, name,
	    sizeof(hash_table[hashindex].name));
	return (hashindex);
}

/*
 * Get a userid->name mapping from the system.
 * If the passwd database is hashed (#define RANDOM_PW), we
 * just handle this uid.  Otherwise we scan the passwd file
 * and cache any entries we pass over while looking.
 */
static int
get_user(uid_t uid)
{
	struct passwd *pwd;

#ifdef RANDOM_PW
	/* no performance penalty for using getpwuid makes it easy */
	if ((pwd = getpwuid(uid)) != NULL)
		return (enter_user(pwd->pw_uid, pwd->pw_name, 1));
#else

	int from_start = 0;

	/*
	 *  If we just called getpwuid each time, things would be very slow
	 *  since that just iterates through the passwd file each time.  So,
	 *  we walk through the file instead (using getpwent) and cache each
	 *  entry as we go.  Once the right record is found, we cache it and
	 *  return immediately.  The next time we come in, getpwent will get
	 *  the next record.  In theory, we never have to read the passwd file
	 *  a second time (because we cache everything we read).  But in
	 *  practice, the cache may not be large enough, so if we don't find
	 *  it the first time we have to scan the file a second time.  This
	 *  is not very efficient, but it will do for now.
	 */
	while (from_start++ < 2) {
		while ((pwd = getpwent()) != NULL) {
			if (pwd->pw_uid == uid)
				return (enter_user(pwd->pw_uid, pwd->pw_name, 1));
			(void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
		}
		/* try again */
		setpwent();
	}
#endif
	/* if we can't find the name at all, then use the uid as the name */
	return (enter_user(uid, itoa7(uid), 1));
}