1 /*
2 * Top users/processes display for Unix
3 *
4 * This program may be freely redistributed,
5 * but this entire comment MUST remain intact.
6 *
7 * Copyright (c) 1984, 1989, William LeFebvre, Rice University
8 * Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
9 */
10
11 /*
12 * Username translation code for top.
13 *
14 * These routines handle uid to username mapping.
15 * They use a hashing table scheme to reduce reading overhead.
16 * For the time being, these are very straightforward hashing routines.
17 * Maybe someday I'll put in something better. But with the advent of
18 * "random access" password files, it might not be worth the effort.
19 *
20 * Changes to these have been provided by John Gilmore (gnu@toad.com).
21 *
22 * The hash has been simplified in this release, to avoid the
23 * table overflow problems of previous releases. If the value
24 * at the initial hash location is not right, it is replaced
25 * by the right value. Collisions will cause us to call getpw*
26 * but hey, this is a cache, not the Library of Congress.
27 * This makes the table size independent of the passwd file size.
28 */
29
30 #include <sys/param.h>
31
32 #include <pwd.h>
33 #include <stdbool.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37
38 #include "utils.h"
39 #include "username.h"
40
41 struct hash_el {
42 int uid;
43 char name[MAXLOGNAME];
44 };
45
46 #define is_empty_hash(x) (hash_table[x].name[0] == 0)
47
48 /* simple minded hashing function */
49 #define hashit(i) (abs(i) % Table_size)
50
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 static struct hash_el hash_table[Table_size];
54
55
56 char *
username(int uid)57 username(int uid)
58 {
59 int hashindex;
60
61 hashindex = hashit(uid);
62 if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
63 {
64 /* not here or not right -- get it out of passwd */
65 hashindex = get_user(uid);
66 }
67 return(hash_table[hashindex].name);
68 }
69
70 int
userid(char username_[])71 userid(char username_[])
72 {
73 struct passwd *pwd;
74
75 /* Eventually we want this to enter everything in the hash table,
76 but for now we just do it simply and remember just the result.
77 */
78
79 if ((pwd = getpwnam(username_)) == NULL)
80 {
81 return(-1);
82 }
83
84 /* enter the result in the hash table */
85 enter_user(pwd->pw_uid, username_, 1);
86
87 /* return our result */
88 return(pwd->pw_uid);
89 }
90
91 /* wecare 1 = enter it always, 0 = nice to have */
92 int
enter_user(int uid,char name[],bool wecare)93 enter_user(int uid, char name[], bool wecare)
94 {
95 int hashindex;
96
97 #ifdef DEBUG
98 fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
99 #endif
100
101 hashindex = hashit(uid);
102
103 if (!is_empty_hash(hashindex))
104 {
105 if (!wecare)
106 return (0); /* Don't clobber a slot for trash */
107 if (hash_table[hashindex].uid == uid)
108 return(hashindex); /* Fortuitous find */
109 }
110
111 /* empty or wrong slot -- fill it with new value */
112 hash_table[hashindex].uid = uid;
113 (void) strncpy(hash_table[hashindex].name, name, MAXLOGNAME - 1);
114 return(hashindex);
115 }
116
117 /*
118 * Get a userid->name mapping from the system.
119 */
120
121 int
get_user(int uid)122 get_user(int uid)
123 {
124 struct passwd *pwd;
125
126 /* no performance penalty for using getpwuid makes it easy */
127 if ((pwd = getpwuid(uid)) != NULL)
128 {
129 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
130 }
131
132 /* if we can't find the name at all, then use the uid as the name */
133 return(enter_user(uid, itoa7(uid), 1));
134 }
135