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 Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #ifdef 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 #ifdef HAVE_UNISTD_H
  34 #include <unistd.h>
  35 #endif
  36 #ifndef _POSIX_VERSION
  37 struct passwd *getpwuid ();
  38 struct passwd *getpwnam ();
  39 struct group *getgrgid ();
  40 struct group *getgrnam ();
  41 #endif
  42
  43 char *xmalloc ();
  44 char *xstrdup ();
  45
  46 struct userid
  47 {
  48   union
  49     {
  50       uid_t u;
  51       gid_t g;
  52     } id;
  53   char *name;
  54   struct userid *next;
  55 };
  56
  57 static struct userid *user_alist;
  58
  59 /* The members of this list have names not in the local passwd file.  */
  60 static struct userid *nouser_alist;
  61
  62 /* Translate UID to a login name or a stringified number,
  63    with cache.  */
  64
  65 char *
  66 getuser (uid)
  67      uid_t uid;
  68 {
  69   register struct userid *tail;
  70   struct passwd *pwent;
  71   char usernum_string[20];
  72
  73   for (tail = user_alist; tail; tail = tail->next)
  74     if (tail->id.u == uid)
  75       return tail->name;
  76
  77   pwent = getpwuid (uid);
  78   tail = (struct userid *) xmalloc (sizeof (struct userid));
  79   tail->id.u = uid;
  80   if (pwent == 0)
  81     {
  82       sprintf (usernum_string, "%u", (unsigned) uid);
  83       tail->name = xstrdup (usernum_string);
  84     }
  85   else
  86     tail->name = xstrdup (pwent->pw_name);
  87
  88   /* Add to the head of the list, so most recently used is first.  */
  89   tail->next = user_alist;
  90   user_alist = tail;
  91   return tail->name;
  92 }
  93
  94 /* Translate USER to a UID, with cache.
  95    Return NULL if there is no such user.
  96    (We also cache which user names have no passwd entry,
  97    so we don't keep looking them up.)  */
  98
  99 uid_t *
 100 getuidbyname (user)
 101      char *user;
 102 {
 103   register struct userid *tail;
 104   struct passwd *pwent;
 105
 106   for (tail = user_alist; tail; tail = tail->next)
 107     /* Avoid a function call for the most common case.  */
 108     if (*tail->name == *user && !strcmp (tail->name, user))
 109       return &tail->id.u;
 110
 111   for (tail = nouser_alist; tail; tail = tail->next)
 112     /* Avoid a function call for the most common case.  */
 113     if (*tail->name == *user && !strcmp (tail->name, user))
 114       return 0;
 115
 116   pwent = getpwnam (user);
 117
 118   tail = (struct userid *) xmalloc (sizeof (struct userid));
 119   tail->name = xstrdup (user);
 120
 121   /* Add to the head of the list, so most recently used is first.  */
 122   if (pwent)
 123     {
 124       tail->id.u = pwent->pw_uid;
 125       tail->next = user_alist;
 126       user_alist = tail;
 127       return &tail->id.u;
 128     }
 129
 130   tail->next = nouser_alist;
 131   nouser_alist = tail;
 132   return 0;
 133 }
 134
 135 /* Use the same struct as for userids.  */
 136 static struct userid *group_alist;
 137 static struct userid *nogroup_alist;
 138
 139 /* Translate GID to a group name or a stringified number,
 140    with cache.  */
 141
 142 char *
 143 getgroup (gid)
 144      gid_t gid;
 145 {
 146   register struct userid *tail;
 147   struct group *grent;
 148   char groupnum_string[20];
 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   if (grent == 0)
 158     {
 159       sprintf (groupnum_string, "%u", (unsigned int) gid);
 160       tail->name = xstrdup (groupnum_string);
 161     }
 162   else
 163     tail->name = xstrdup (grent->gr_name);
 164
 165   /* Add to the head of the list, so most recently used is first.  */
 166   tail->next = group_alist;
 167   group_alist = tail;
 168   return tail->name;
 169 }
 170
 171 /* Translate GROUP to a UID, with cache.
 172    Return NULL if there is no such group.
 173    (We also cache which group names have no group entry,
 174    so we don't keep looking them up.)  */
 175
 176 gid_t *
 177 getgidbyname (group)
 178      char *group;
 179 {
 180   register struct userid *tail;
 181   struct group *grent;
 182
 183   for (tail = group_alist; tail; tail = tail->next)
 184     /* Avoid a function call for the most common case.  */
 185     if (*tail->name == *group && !strcmp (tail->name, group))
 186       return &tail->id.g;
 187
 188   for (tail = nogroup_alist; tail; tail = tail->next)
 189     /* Avoid a function call for the most common case.  */
 190     if (*tail->name == *group && !strcmp (tail->name, group))
 191       return 0;
 192
 193   grent = getgrnam (group);
 194
 195   tail = (struct userid *) xmalloc (sizeof (struct userid));
 196   tail->name = xstrdup (group);
 197
 198   /* Add to the head of the list, so most recently used is first.  */
 199   if (grent)
 200     {
 201       tail->id.g = grent->gr_gid;
 202       tail->next = group_alist;
 203       group_alist = tail;
 204       return &tail->id.g;
 205     }
 206
 207   tail->next = nogroup_alist;
 208   nogroup_alist = tail;
 209   return 0;
 210 }