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>
41 #include "top.local.h"
47 char name[MAXLOGNAME];
50 #define is_empty_hash(x) (hash_table[x].name[0] == 0)
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
56 #define hashit(i) (abs(i) % Table_size)
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! */
60 struct hash_el hash_table[Table_size];
70 hashindex = hashit(uid);
71 if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
73 /* not here or not right -- get it out of passwd */
74 hashindex = get_user(uid);
76 return(hash_table[hashindex].name);
86 /* Eventually we want this to enter everything in the hash table,
87 but for now we just do it simply and remember just the result.
90 if ((pwd = getpwnam(username)) == NULL)
95 /* enter the result in the hash table */
96 enter_user(pwd->pw_uid, username, 1);
98 /* return our result */
102 int enter_user(uid, name, wecare)
106 int wecare; /* 1 = enter it always, 0 = nice to have */
112 fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
115 hashindex = hashit(uid);
117 if (!is_empty_hash(hashindex))
120 return 0; /* Don't clobber a slot for trash */
121 if (hash_table[hashindex].uid == uid)
122 return(hashindex); /* Fortuitous find */
125 /* empty or wrong slot -- fill it with new value */
126 hash_table[hashindex].uid = uid;
127 (void) strncpy(hash_table[hashindex].name, name, MAXLOGNAME - 1);
132 * Get a userid->name mapping from the system.
133 * If the passwd database is hashed (#define RANDOM_PW), we
134 * just handle this uid. Otherwise we scan the passwd file
135 * and cache any entries we pass over while looking.
146 /* no performance penalty for using getpwuid makes it easy */
147 if ((pwd = getpwuid(uid)) != NULL)
149 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
156 * If we just called getpwuid each time, things would be very slow
157 * since that just iterates through the passwd file each time. So,
158 * we walk through the file instead (using getpwent) and cache each
159 * entry as we go. Once the right record is found, we cache it and
160 * return immediately. The next time we come in, getpwent will get
161 * the next record. In theory, we never have to read the passwd file
162 * a second time (because we cache everything we read). But in
163 * practice, the cache may not be large enough, so if we don't find
164 * it the first time we have to scan the file a second time. This
165 * is not very efficient, but it will do for now.
168 while (from_start++ < 2)
170 while ((pwd = getpwent()) != NULL)
172 if (pwd->pw_uid == uid)
174 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
176 (void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
182 /* if we can't find the name at all, then use the uid as the name */
183 return(enter_user(uid, itoa7(uid), 1));