2 * Top users/processes display for Unix
5 * This program may be freely redistributed,
6 * but this entire comment MUST remain intact.
8 * Copyright (c) 1984, 1989, William LeFebvre, Rice University
9 * Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
15 * Username translation code for top.
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.
23 * Changes to these have been provided by John Gilmore (gnu@toad.com).
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.
33 #include <sys/param.h>
34 #include <sys/types.h>
38 #include "top.local.h"
43 char name[MAXLOGNAME];
46 #define is_empty_hash(x) (hash_table[x].name[0] == 0)
48 /* simple minded hashing function */
49 /* Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
50 the hash_table. Applied abs() function to fix. 2/16/96 tpugh
52 #define hashit(i) (abs(i) % Table_size)
54 /* K&R requires that statically declared tables be initialized to zero. */
55 /* We depend on that for hash_table and YOUR compiler had BETTER do it! */
56 struct hash_el hash_table[Table_size];
62 * There used to be some steps we had to take to initialize things.
63 * We don't need to do that anymore, but we will leave this stub in
64 * just in case future changes require initialization steps.
73 register int hashindex;
75 hashindex = hashit(uid);
76 if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
78 /* not here or not right -- get it out of passwd */
79 hashindex = get_user(uid);
81 return(hash_table[hashindex].name);
91 /* Eventually we want this to enter everything in the hash table,
92 but for now we just do it simply and remember just the result.
95 if ((pwd = getpwnam(username)) == NULL)
100 /* enter the result in the hash table */
101 enter_user(pwd->pw_uid, username, 1);
103 /* return our result */
107 int enter_user(uid, name, wecare)
111 int wecare; /* 1 = enter it always, 0 = nice to have */
114 register int hashindex;
117 fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
120 hashindex = hashit(uid);
122 if (!is_empty_hash(hashindex))
125 return 0; /* Don't clobber a slot for trash */
126 if (hash_table[hashindex].uid == uid)
127 return(hashindex); /* Fortuitous find */
130 /* empty or wrong slot -- fill it with new value */
131 hash_table[hashindex].uid = uid;
132 (void) strncpy(hash_table[hashindex].name, name, MAXLOGNAME - 1);
137 * Get a userid->name mapping from the system.
138 * If the passwd database is hashed (#define RANDOM_PW), we
139 * just handle this uid. Otherwise we scan the passwd file
140 * and cache any entries we pass over while looking.
151 /* no performance penalty for using getpwuid makes it easy */
152 if ((pwd = getpwuid(uid)) != NULL)
154 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
161 * If we just called getpwuid each time, things would be very slow
162 * since that just iterates through the passwd file each time. So,
163 * we walk through the file instead (using getpwent) and cache each
164 * entry as we go. Once the right record is found, we cache it and
165 * return immediately. The next time we come in, getpwent will get
166 * the next record. In theory, we never have to read the passwd file
167 * a second time (because we cache everything we read). But in
168 * practice, the cache may not be large enough, so if we don't find
169 * it the first time we have to scan the file a second time. This
170 * is not very efficient, but it will do for now.
173 while (from_start++ < 2)
175 while ((pwd = getpwent()) != NULL)
177 if (pwd->pw_uid == uid)
179 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
181 (void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
187 /* if we can't find the name at all, then use the uid as the name */
188 return(enter_user(uid, itoa7(uid), 1));