1/*
2 *  Top users/processes display for Unix
3 *  Version 3
4 *
5 *  This program may be freely redistributed,
6 *  but this entire comment MUST remain intact.
7 *
8 *  Copyright (c) 1984, 1989, William LeFebvre, Rice University
9 *  Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
10 *
11 * $FreeBSD$
12 */
13
14/*
15 *  Username translation code for top.
16 *
17 *  These routines handle uid to username mapping.
18 *  They use a hashing table scheme to reduce reading overhead.
19 *  For the time being, these are very straightforward hashing routines.
20 *  Maybe someday I'll put in something better.  But with the advent of
21 *  "random access" password files, it might not be worth the effort.
22 *
23 *  Changes to these have been provided by John Gilmore (gnu@toad.com).
24 *
25 *  The hash has been simplified in this release, to avoid the
26 *  table overflow problems of previous releases.  If the value
27 *  at the initial hash location is not right, it is replaced
28 *  by the right value.  Collisions will cause us to call getpw*
29 *  but hey, this is a cache, not the Library of Congress.
30 *  This makes the table size independent of the passwd file size.
31 */
32
33#include <sys/param.h>
34#include <sys/types.h>
35
36#include <pwd.h>
37#include <stdio.h>
38#include <stdlib.h>
39#include <string.h>
40
41#include "top.local.h"
42#include "utils.h"
43#include "username.h"
44
45struct hash_el {
46    int  uid;
47    char name[MAXLOGNAME];
48};
49
50#define    is_empty_hash(x)	(hash_table[x].name[0] == 0)
51
52/* simple minded hashing function */
53/* Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
54   the hash_table.  Applied abs() function to fix. 2/16/96 tpugh
55*/
56#define    hashit(i)	(abs(i) % Table_size)
57
58/* K&R requires that statically declared tables be initialized to zero. */
59/* We depend on that for hash_table and YOUR compiler had BETTER do it! */
60struct hash_el hash_table[Table_size];
61
62
63void
64init_hash()
65
66{
67    /*
68     *  There used to be some steps we had to take to initialize things.
69     *  We don't need to do that anymore, but we will leave this stub in
70     *  just in case future changes require initialization steps.
71     */
72}
73
74char *username(uid)
75
76int uid;
77
78{
79    register int hashindex;
80
81    hashindex = hashit(uid);
82    if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
83    {
84	/* not here or not right -- get it out of passwd */
85	hashindex = get_user(uid);
86    }
87    return(hash_table[hashindex].name);
88}
89
90int userid(username)
91
92char *username;
93
94{
95    struct passwd *pwd;
96
97    /* Eventually we want this to enter everything in the hash table,
98       but for now we just do it simply and remember just the result.
99     */
100
101    if ((pwd = getpwnam(username)) == NULL)
102    {
103	return(-1);
104    }
105
106    /* enter the result in the hash table */
107    enter_user(pwd->pw_uid, username, 1);
108
109    /* return our result */
110    return(pwd->pw_uid);
111}
112
113int enter_user(uid, name, wecare)
114
115int  uid;
116char *name;
117int wecare;		/* 1 = enter it always, 0 = nice to have */
118
119{
120    register int hashindex;
121
122#ifdef DEBUG
123    fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
124#endif
125
126    hashindex = hashit(uid);
127
128    if (!is_empty_hash(hashindex))
129    {
130	if (!wecare)
131	    return 0;		/* Don't clobber a slot for trash */
132	if (hash_table[hashindex].uid == uid)
133	    return(hashindex);	/* Fortuitous find */
134    }
135
136    /* empty or wrong slot -- fill it with new value */
137    hash_table[hashindex].uid = uid;
138    (void) strncpy(hash_table[hashindex].name, name, MAXLOGNAME - 1);
139    return(hashindex);
140}
141
142/*
143 * Get a userid->name mapping from the system.
144 * If the passwd database is hashed (#define RANDOM_PW), we
145 * just handle this uid.  Otherwise we scan the passwd file
146 * and cache any entries we pass over while looking.
147 */
148
149int get_user(uid)
150
151int uid;
152
153{
154    struct passwd *pwd;
155
156#ifdef RANDOM_PW
157    /* no performance penalty for using getpwuid makes it easy */
158    if ((pwd = getpwuid(uid)) != NULL)
159    {
160	return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
161    }
162#else
163
164    int from_start = 0;
165
166    /*
167     *  If we just called getpwuid each time, things would be very slow
168     *  since that just iterates through the passwd file each time.  So,
169     *  we walk through the file instead (using getpwent) and cache each
170     *  entry as we go.  Once the right record is found, we cache it and
171     *  return immediately.  The next time we come in, getpwent will get
172     *  the next record.  In theory, we never have to read the passwd file
173     *  a second time (because we cache everything we read).  But in
174     *  practice, the cache may not be large enough, so if we don't find
175     *  it the first time we have to scan the file a second time.  This
176     *  is not very efficient, but it will do for now.
177     */
178
179    while (from_start++ < 2)
180    {
181	while ((pwd = getpwent()) != NULL)
182	{
183	    if (pwd->pw_uid == uid)
184	    {
185		return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
186	    }
187	    (void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
188	}
189	/* try again */
190	setpwent();
191    }
192#endif
193    /* if we can't find the name at all, then use the uid as the name */
194    return(enter_user(uid, itoa7(uid), 1));
195}
196