lib/idcache.c

   1 /* idcache.c -- map user and group IDs, cached for speed
   2    Copyright (C) 1985, 1988, 1989, 1990, 1997 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <stdio.h>
  23 #include <sys/types.h>
  24 #include <pwd.h>
  25 #include <grp.h>
  26
  27 #if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
  28 # include <string.h>
  29 #else
  30 # include <strings.h>
  31 #endif
  32
  33 #if HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36
  37 #ifndef _POSIX_VERSION
  38 struct passwd *getpwuid ();
  39 struct passwd *getpwnam ();
  40 struct group *getgrgid ();
  41 struct group *getgrnam ();
  42 #endif
  43
  44 char *xmalloc ();
  45 char *xstrdup ();
  46
  47 struct userid
  48 {
  49   union
  50     {
  51       uid_t u;
  52       gid_t g;
  53     } id;
  54   char *name;
  55   struct userid *next;
  56 };
  57
  58 /* The members of this list have already been looked up.
  59    If a name is NULL, the corresponding id is not in the password file.  */
  60 static struct userid *user_alist;
  61
  62 #ifdef NOT_USED
  63 /* The members of this list are names not in the local passwd file;
  64    their names are always not NULL, and their ids are irrelevant.  */
  65 static struct userid *nouser_alist;
  66 #endif /* NOT_USED */
  67
  68 /* Translate UID to a login name, with cache.
  69    If UID cannot be resolved, return NULL.
  70    Cache lookup failures, too.  */
  71
  72 char *
  73 getuser (uid)
  74      uid_t uid;
  75 {
  76   register struct userid *tail;
  77   struct passwd *pwent;
  78
  79   for (tail = user_alist; tail; tail = tail->next)
  80     if (tail->id.u == uid)
  81       return tail->name;
  82
  83   pwent = getpwuid (uid);
  84   tail = (struct userid *) xmalloc (sizeof (struct userid));
  85   tail->id.u = uid;
  86   tail->name = (pwent ? xstrdup (pwent->pw_name) : NULL);
  87
  88   /* Add to the head of the list, so most recently added is first.  */
  89   tail->next = user_alist;
  90   user_alist = tail;
  91   return tail->name;
  92 }
  93
  94 #ifdef NOT_USED
  95
  96 /* Translate USER to a UID, with cache.
  97    Return NULL if there is no such user.
  98    (We also cache which user names have no passwd entry,
  99    so we don't keep looking them up.)  */
 100
 101 uid_t *
 102 getuidbyname (user)
 103      const char *user;
 104 {
 105   register struct userid *tail;
 106   struct passwd *pwent;
 107
 108   for (tail = user_alist; tail; tail = tail->next)
 109     /* Avoid a function call for the most common case.  */
 110     if (tail->name && *tail->name == *user && !strcmp (tail->name, user))
 111       return &tail->id.u;
 112
 113   for (tail = nouser_alist; tail; tail = tail->next)
 114     /* Avoid a function call for the most common case.  */
 115     if (*tail->name == *user && !strcmp (tail->name, user))
 116       return 0;
 117
 118   pwent = getpwnam (user);
 119
 120   tail = (struct userid *) xmalloc (sizeof (struct userid));
 121   tail->name = xstrdup (user);
 122
 123   /* Add to the head of the list, so most recently added is first.  */
 124   if (pwent)
 125     {
 126       tail->id.u = pwent->pw_uid;
 127       tail->next = user_alist;
 128       user_alist = tail;
 129       return &tail->id.u;
 130     }
 131
 132   tail->next = nouser_alist;
 133   nouser_alist = tail;
 134   return 0;
 135 }
 136
 137 #endif /* NOT_USED */
 138
 139 /* Use the same struct as for userids.  */
 140 static struct userid *group_alist;
 141 #ifdef NOT_USED
 142 static struct userid *nogroup_alist;
 143 #endif
 144
 145 /* Translate GID to a group name, with cache.
 146    Return NULL if the group has no name.  */
 147
 148 char *
 149 getgroup (gid)
 150      gid_t gid;
 151 {
 152   register struct userid *tail;
 153   struct group *grent;
 154
 155   for (tail = group_alist; tail; tail = tail->next)
 156     if (tail->id.g == gid)
 157       return tail->name;
 158
 159   grent = getgrgid (gid);
 160   tail = (struct userid *) xmalloc (sizeof (struct userid));
 161   tail->id.g = gid;
 162   tail->name = (grent ? xstrdup (grent->gr_name) : NULL);
 163
 164   /* Add to the head of the list, so most recently used is first.  */
 165   tail->next = group_alist;
 166   group_alist = tail;
 167   return tail->name;
 168 }
 169
 170 #ifdef NOT_USED
 171
 172 /* Translate GROUP to a GID, with cache.
 173    Return NULL if there is no such group.
 174    (We also cache which group names have no group entry,
 175    so we don't keep looking them up.)  */
 176
 177 gid_t *
 178 getgidbyname (group)
 179      const char *group;
 180 {
 181   register struct userid *tail;
 182   struct group *grent;
 183
 184   for (tail = group_alist; tail; tail = tail->next)
 185     /* Avoid a function call for the most common case.  */
 186     if (tail->name && *tail->name == *group && !strcmp (tail->name, group))
 187       return &tail->id.g;
 188
 189   for (tail = nogroup_alist; tail; tail = tail->next)
 190     /* Avoid a function call for the most common case.  */
 191     if (*tail->name == *group && !strcmp (tail->name, group))
 192       return 0;
 193
 194   grent = getgrnam (group);
 195
 196   tail = (struct userid *) xmalloc (sizeof (struct userid));
 197   tail->name = xstrdup (group);
 198
 199   /* Add to the head of the list, so most recently used is first.  */
 200   if (grent)
 201     {
 202       tail->id.g = grent->gr_gid;
 203       tail->next = group_alist;
 204       group_alist = tail;
 205       return &tail->id.g;
 206     }
 207
 208   tail->next = nogroup_alist;
 209   nogroup_alist = tail;
 210   return 0;
 211 }
 212
 213 #endif /* NOT_USED */