contrib/top/username.c

   1 /*
   2  *  Top users/processes display for Unix
   3  *  Version 3
   4  *
   5  *  This program may be freely redistributed,
   6  *  but this entire comment MUST remain intact.
   7  *
   8  *  Copyright (c) 1984, 1989, William LeFebvre, Rice University
   9  *  Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
  10  *
  11  * $FreeBSD: src/contrib/top/username.c,v 1.2.8.1 2002/08/11 17:09:25 dwmalone Exp $
  12  * $DragonFly: src/contrib/top/username.c,v 1.2 2003/06/17 04:24:07 dillon Exp $
  13  */
  14
  15 /*
  16  *  Username translation code for top.
  17  *
  18  *  These routines handle uid to username mapping.
  19  *  They use a hashing table scheme to reduce reading overhead.
  20  *  For the time being, these are very straightforward hashing routines.
  21  *  Maybe someday I'll put in something better.  But with the advent of
  22  *  "random access" password files, it might not be worth the effort.
  23  *
  24  *  Changes to these have been provided by John Gilmore (gnu@toad.com).
  25  *
  26  *  The hash has been simplified in this release, to avoid the
  27  *  table overflow problems of previous releases.  If the value
  28  *  at the initial hash location is not right, it is replaced
  29  *  by the right value.  Collisions will cause us to call getpw*
  30  *  but hey, this is a cache, not the Library of Congress.
  31  *  This makes the table size independent of the passwd file size.
  32  */
  33
  34 #include <sys/types.h>
  35 #include <stdio.h>
  36 #include <pwd.h>
  37 #include <utmp.h>
  38
  39 #include "top.local.h"
  40 #include "utils.h"
  41
  42 struct hash_el {
  43     int  uid;
  44     char name[UT_NAMESIZE + 1];
  45 };
  46
  47 #define    is_empty_hash(x)     (hash_table[x].name[0] == 0)
  48
  49 /* simple minded hashing function */
  50 /* Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
  51    the hash_table.  Applied abs() function to fix. 2/16/96 tpugh
  52 */
  53 #define    hashit(i)    (abs(i) % Table_size)
  54
  55 /* K&R requires that statically declared tables be initialized to zero. */
  56 /* We depend on that for hash_table and YOUR compiler had BETTER do it! */
  57 struct hash_el hash_table[Table_size];
  58
  59 init_hash()
  60
  61 {
  62     /*
  63      *  There used to be some steps we had to take to initialize things.
  64      *  We don't need to do that anymore, but we will leave this stub in
  65      *  just in case future changes require initialization steps.
  66      */
  67 }
  68
  69 char *username(uid)
  70
  71 register int uid;
  72
  73 {
  74     register int hashindex;
  75
  76     hashindex = hashit(uid);
  77     if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
  78     {
  79         /* not here or not right -- get it out of passwd */
  80         hashindex = get_user(uid);
  81     }
  82     return(hash_table[hashindex].name);
  83 }
  84
  85 int userid(username)
  86
  87 char *username;
  88
  89 {
  90     struct passwd *pwd;
  91
  92     /* Eventually we want this to enter everything in the hash table,
  93        but for now we just do it simply and remember just the result.
  94      */
  95
  96     if ((pwd = getpwnam(username)) == NULL)
  97     {
  98         return(-1);
  99     }
 100
 101     /* enter the result in the hash table */
 102     enter_user(pwd->pw_uid, username, 1);
 103
 104     /* return our result */
 105     return(pwd->pw_uid);
 106 }
 107
 108 int enter_user(uid, name, wecare)
 109
 110 register int  uid;
 111 register char *name;
 112 int wecare;             /* 1 = enter it always, 0 = nice to have */
 113
 114 {
 115     register int hashindex;
 116
 117 #ifdef DEBUG
 118     fprintf(stderr, "enter_hash(%d, %s, %d)\n", uid, name, wecare);
 119 #endif
 120
 121     hashindex = hashit(uid);
 122
 123     if (!is_empty_hash(hashindex))
 124     {
 125         if (!wecare)
 126             return 0;           /* Don't clobber a slot for trash */
 127         if (hash_table[hashindex].uid == uid)
 128             return(hashindex);  /* Fortuitous find */
 129     }
 130
 131     /* empty or wrong slot -- fill it with new value */
 132     hash_table[hashindex].uid = uid;
 133     (void) strncpy(hash_table[hashindex].name, name, UT_NAMESIZE);
 134     return(hashindex);
 135 }
 136
 137 /*
 138  * Get a userid->name mapping from the system.
 139  * If the passwd database is hashed (#define RANDOM_PW), we
 140  * just handle this uid.  Otherwise we scan the passwd file
 141  * and cache any entries we pass over while looking.
 142  */
 143
 144 int get_user(uid)
 145
 146 register int uid;
 147
 148 {
 149     struct passwd *pwd;
 150
 151 #ifdef RANDOM_PW
 152     /* no performance penalty for using getpwuid makes it easy */
 153     if ((pwd = getpwuid(uid)) != NULL)
 154     {
 155         return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
 156     }
 157 #else
 158
 159     int from_start = 0;
 160
 161     /*
 162      *  If we just called getpwuid each time, things would be very slow
 163      *  since that just iterates through the passwd file each time.  So,
 164      *  we walk through the file instead (using getpwent) and cache each
 165      *  entry as we go.  Once the right record is found, we cache it and
 166      *  return immediately.  The next time we come in, getpwent will get
 167      *  the next record.  In theory, we never have to read the passwd file
 168      *  a second time (because we cache everything we read).  But in
 169      *  practice, the cache may not be large enough, so if we don't find
 170      *  it the first time we have to scan the file a second time.  This
 171      *  is not very efficient, but it will do for now.
 172      */
 173
 174     while (from_start++ < 2)
 175     {
 176         while ((pwd = getpwent()) != NULL)
 177         {
 178             if (pwd->pw_uid == uid)
 179             {
 180                 return(enter_user(pwd->pw_uid, pwd->pw_name, 1));
 181             }
 182             (void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
 183         }
 184         /* try again */
 185         setpwent();
 186     }
 187 #endif
 188     /* if we can't find the name at all, then use the uid as the name */
 189     return(enter_user(uid, itoa7(uid), 1));
 190 }