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
13 * Username translation code for top.
15 * These routines handle uid to username mapping.
16 * They use a hashing table scheme to reduce reading overhead.
17 * For the time being, these are very straightforward hashing routines.
18 * Maybe someday I'll put in something better. But with the advent of
19 * "random access" password files, it might not be worth the effort.
21 * Changes to these have been provided by John Gilmore (gnu@toad.com).
23 * The hash has been simplified in this release, to avoid the
24 * table overflow problems of previous releases. If the value
25 * at the initial hash location is not right, it is replaced
26 * by the right value. Collisions will cause us to call getpw*
27 * but hey, this is a cache, not the Library of Congress.
28 * This makes the table size independent of the passwd file size.
35 #include "top.local.h"
40 char name[UT_NAMESIZE + 1];
43 #define is_empty_hash(x) (hash_table[x].name[0] == 0)
45 /* simple minded hashing function */
46 /* Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
47 the hash_table. Applied abs() function to fix. 2/16/96 tpugh
49 #define hashit(i) (abs(i) % Table_size)
51 /* K&R requires that statically declared tables be initialized to zero. */
52 /* We depend on that for hash_table and YOUR compiler had BETTER do it! */
53 struct hash_el hash_table[Table_size];
59 * There used to be some steps we had to take to initialize things.
60 * We don't need to do that anymore, but we will leave this stub in
61 * just in case future changes require initialization steps.
70 register int hashindex;
72 hashindex = hashit(uid);
73 if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
75 /* not here or not right -- get it out of passwd */
76 hashindex = get_user(uid);
78 return(hash_table[hashindex].name);
88 /* Eventually we want this to enter everything in the hash table,
89 but for now we just do it simply and remember just the result.
92 if ((pwd = getpwnam(username)) == NULL)
97 /* enter the result in the hash table */
98 enter_user(pwd->pw_uid, username, 1);
100 /* return our result */
104 int enter_user(uid, name, wecare)
108 int wecare; /* 1 = enter it always, 0 = nice to have */
111 register int hashindex;
114 fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
117 hashindex = hashit(uid);
119 if (!is_empty_hash(hashindex))
122 return 0; /* Don't clobber a slot for trash */
123 if (hash_table[hashindex].uid == uid)
124 return(hashindex); /* Fortuitous find */
127 /* empty or wrong slot -- fill it with new value */
128 hash_table[hashindex].uid = uid;
129 (void) strncpy(hash_table[hashindex].name, name, UT_NAMESIZE);
134 * Get a userid->name mapping from the system.
135 * If the passwd database is hashed (#define RANDOM_PW), we
136 * just handle this uid. Otherwise we scan the passwd file
137 * and cache any entries we pass over while looking.
148 /* no performance penalty for using getpwuid makes it easy */
149 if ((pwd = getpwuid(uid)) != NULL)
151 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
158 * If we just called getpwuid each time, things would be very slow
159 * since that just iterates through the passwd file each time. So,
160 * we walk through the file instead (using getpwent) and cache each
161 * entry as we go. Once the right record is found, we cache it and
162 * return immediately. The next time we come in, getpwent will get
163 * the next record. In theory, we never have to read the passwd file
164 * a second time (because we cache everything we read). But in
165 * practice, the cache may not be large enough, so if we don't find
166 * it the first time we have to scan the file a second time. This
167 * is not very efficient, but it will do for now.
170 while (from_start++ < 2)
172 while ((pwd = getpwent()) != NULL)
174 if (pwd->pw_uid == uid)
176 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
178 (void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
184 /* if we can't find the name at all, then use the uid as the name */
185 return(enter_user(uid, itoa7(uid), 1));