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 static struct userid *user_alist;
  59
  60 #ifdef NOT_USED
  61 /* The members of this list have names not in the local passwd file.  */
  62 static struct userid *nouser_alist;
  63 #endif /* NOT_USED */
  64
  65 /* Translate UID to a login name, with cache.
  66    If UID cannot be resolved, return NULL.
  67    Cache lookup failures, too.  */
  68
  69 char *
  70 getuser (uid)
  71      uid_t uid;
  72 {
  73   register struct userid *tail;
  74   struct passwd *pwent;
  75
  76   for (tail = user_alist; tail; tail = tail->next)
  77     if (tail->id.u == uid)
  78       return tail->name;
  79
  80   pwent = getpwuid (uid);
  81   tail = (struct userid *) xmalloc (sizeof (struct userid));
  82   tail->id.u = uid;
  83   tail->name = (pwent ? xstrdup (pwent->pw_name) : NULL);
  84
  85   /* Add to the head of the list, so most recently used is first.  */
  86   tail->next = user_alist;
  87   user_alist = tail;
  88   return tail->name;
  89 }
  90
  91 #ifdef NOT_USED
  92
  93 /* Translate USER to a UID, with cache.
  94    Return NULL if there is no such user.
  95    (We also cache which user names have no passwd entry,
  96    so we don't keep looking them up.)  */
  97
  98 uid_t *
  99 getuidbyname (user)
 100      const char *user;
 101 {
 102   register struct userid *tail;
 103   struct passwd *pwent;
 104
 105   for (tail = user_alist; tail; tail = tail->next)
 106     /* Avoid a function call for the most common case.  */
 107     if (*tail->name == *user && !strcmp (tail->name, user))
 108       return &tail->id.u;
 109
 110   for (tail = nouser_alist; tail; tail = tail->next)
 111     /* Avoid a function call for the most common case.  */
 112     if (*tail->name == *user && !strcmp (tail->name, user))
 113       return 0;
 114
 115   pwent = getpwnam (user);
 116
 117   tail = (struct userid *) xmalloc (sizeof (struct userid));
 118   tail->name = xstrdup (user);
 119
 120   /* Add to the head of the list, so most recently used is first.  */
 121   if (pwent)
 122     {
 123       tail->id.u = pwent->pw_uid;
 124       tail->next = user_alist;
 125       user_alist = tail;
 126       return &tail->id.u;
 127     }
 128
 129   tail->next = nouser_alist;
 130   nouser_alist = tail;
 131   return 0;
 132 }
 133
 134 #endif /* NOT_USED */
 135
 136 /* Use the same struct as for userids.  */
 137 static struct userid *group_alist;
 138 static struct userid *nogroup_alist;
 139
 140 /* Translate GID to a group name or a stringified number,
 141    with cache.  */
 142
 143 char *
 144 getgroup (gid)
 145      gid_t gid;
 146 {
 147   register struct userid *tail;
 148   struct group *grent;
 149
 150   for (tail = group_alist; tail; tail = tail->next)
 151     if (tail->id.g == gid)
 152       return tail->name;
 153
 154   grent = getgrgid (gid);
 155   tail = (struct userid *) xmalloc (sizeof (struct userid));
 156   tail->id.g = gid;
 157   tail->name = (grent ? xstrdup (grent->gr_name) : NULL);
 158
 159   /* Add to the head of the list, so most recently used is first.  */
 160   tail->next = group_alist;
 161   group_alist = tail;
 162   return tail->name;
 163 }
 164
 165 #ifdef NOT_USED
 166
 167 /* Translate GROUP to a GID, with cache.
 168    Return NULL if there is no such group.
 169    (We also cache which group names have no group entry,
 170    so we don't keep looking them up.)  */
 171
 172 gid_t *
 173 getgidbyname (group)
 174      const char *group;
 175 {
 176   register struct userid *tail;
 177   struct group *grent;
 178
 179   for (tail = group_alist; tail; tail = tail->next)
 180     /* Avoid a function call for the most common case.  */
 181     if (*tail->name == *group && !strcmp (tail->name, group))
 182       return &tail->id.g;
 183
 184   for (tail = nogroup_alist; tail; tail = tail->next)
 185     /* Avoid a function call for the most common case.  */
 186     if (*tail->name == *group && !strcmp (tail->name, group))
 187       return 0;
 188
 189   grent = getgrnam (group);
 190
 191   tail = (struct userid *) xmalloc (sizeof (struct userid));
 192   tail->name = xstrdup (group);
 193
 194   /* Add to the head of the list, so most recently used is first.  */
 195   if (grent)
 196     {
 197       tail->id.g = grent->gr_gid;
 198       tail->next = group_alist;
 199       group_alist = tail;
 200       return &tail->id.g;
 201     }
 202
 203   tail->next = nogroup_alist;
 204   nogroup_alist = tail;
 205   return 0;
 206 }
 207
 208 #endif /* NOT_USED */