lib/idcache.c

   1 /* idcache.c -- map user and group IDs, cached for speed
   2    Copyright (C) 1985, 1988, 1989, 1990 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
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 #include <stdio.h>
  19 #include <sys/types.h>
  20 #include <pwd.h>
  21 #include <grp.h>
  22
  23 #if defined(USG) || defined(STDC_HEADERS)
  24 #include <string.h>
  25 #else
  26 #include <strings.h>
  27 #endif
  28
  29 #ifdef HAVE_UNISTD_H
  30 #include <unistd.h>
  31 #endif
  32 #ifndef _POSIX_VERSION
  33 struct passwd *getpwuid ();
  34 struct passwd *getpwnam ();
  35 struct group *getgrgid ();
  36 struct group *getgrnam ();
  37 #endif
  38
  39 char *xmalloc ();
  40 char *xstrdup ();
  41
  42 struct userid
  43 {
  44   union
  45     {
  46       uid_t u;
  47       gid_t g;
  48     } id;
  49   char *name;
  50   struct userid *next;
  51 };
  52
  53 static struct userid *user_alist;
  54
  55 /* The members of this list have names not in the local passwd file.  */
  56 static struct userid *nouser_alist;
  57
  58 /* Translate UID to a login name or a stringified number,
  59    with cache.  */
  60
  61 char *
  62 getuser (uid)
  63      uid_t uid;
  64 {
  65   register struct userid *tail;
  66   struct passwd *pwent;
  67   char usernum_string[20];
  68
  69   for (tail = user_alist; tail; tail = tail->next)
  70     if (tail->id.u == uid)
  71       return tail->name;
  72
  73   pwent = getpwuid (uid);
  74   tail = (struct userid *) xmalloc (sizeof (struct userid));
  75   tail->id.u = uid;
  76   if (pwent == 0)
  77     {
  78       sprintf (usernum_string, "%u", (unsigned) uid);
  79       tail->name = xstrdup (usernum_string);
  80     }
  81   else
  82     tail->name = xstrdup (pwent->pw_name);
  83
  84   /* Add to the head of the list, so most recently used is first.  */
  85   tail->next = user_alist;
  86   user_alist = tail;
  87   return tail->name;
  88 }
  89
  90 /* Translate USER to a UID, with cache.
  91    Return NULL if there is no such user.
  92    (We also cache which user names have no passwd entry,
  93    so we don't keep looking them up.)  */
  94
  95 uid_t *
  96 getuidbyname (user)
  97      char *user;
  98 {
  99   register struct userid *tail;
 100   struct passwd *pwent;
 101
 102   for (tail = user_alist; tail; tail = tail->next)
 103     /* Avoid a function call for the most common case.  */
 104     if (*tail->name == *user && !strcmp (tail->name, user))
 105       return &tail->id.u;
 106
 107   for (tail = nouser_alist; tail; tail = tail->next)
 108     /* Avoid a function call for the most common case.  */
 109     if (*tail->name == *user && !strcmp (tail->name, user))
 110       return 0;
 111
 112   pwent = getpwnam (user);
 113
 114   tail = (struct userid *) xmalloc (sizeof (struct userid));
 115   tail->name = xstrdup (user);
 116
 117   /* Add to the head of the list, so most recently used is first.  */
 118   if (pwent)
 119     {
 120       tail->id.u = pwent->pw_uid;
 121       tail->next = user_alist;
 122       user_alist = tail;
 123       return &tail->id.u;
 124     }
 125
 126   tail->next = nouser_alist;
 127   nouser_alist = tail;
 128   return 0;
 129 }
 130
 131 /* Use the same struct as for userids.  */
 132 static struct userid *group_alist;
 133 static struct userid *nogroup_alist;
 134
 135 /* Translate GID to a group name or a stringified number,
 136    with cache.  */
 137
 138 char *
 139 getgroup (gid)
 140      gid_t gid;
 141 {
 142   register struct userid *tail;
 143   struct group *grent;
 144   char groupnum_string[20];
 145
 146   for (tail = group_alist; tail; tail = tail->next)
 147     if (tail->id.g == gid)
 148       return tail->name;
 149
 150   grent = getgrgid (gid);
 151   tail = (struct userid *) xmalloc (sizeof (struct userid));
 152   tail->id.g = gid;
 153   if (grent == 0)
 154     {
 155       sprintf (groupnum_string, "%u", (unsigned int) gid);
 156       tail->name = xstrdup (groupnum_string);
 157     }
 158   else
 159     tail->name = xstrdup (grent->gr_name);
 160
 161   /* Add to the head of the list, so most recently used is first.  */
 162   tail->next = group_alist;
 163   group_alist = tail;
 164   return tail->name;
 165 }
 166
 167 /* Translate GROUP to a UID, 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      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 }