usr.bin/top/username.c

   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 }