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 * 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 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 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 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