vfs/names.c

   1 /* Look up user and/or group names.
   2    Copyright (C) 1988, 1992 Free Software Foundation
   3
   4    From GNU Tar.
   5
   6 GNU Tar is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU Library General Public License as published
   8 by the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Tar is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU Library General Public License for more details.
  15
  16  * Namespace: finduname, finduid, findgname, findgid.
  17  */
  18
  19 /*
  20  * Look up a user or group name from a uid/gid, maintaining a cache.
  21  * FIXME, for now it's a one-entry cache.
  22  * FIXME2, the "-993" is to reduce the chance of a hit on the first lookup.
  23  * This file should be modified for non-unix systems to do something
  24  * reasonable.
  25  */
  26
  27 #include <config.h>
  28 #include <sys/types.h>
  29 #include <string.h>
  30 #include <unistd.h>
  31 #include <stdio.h>
  32 #include <pwd.h>
  33 #include <grp.h>
  34
  35 #include "names.h"
  36
  37 #ifndef TUNMLEN
  38 #define TUNMLEN 256
  39 #endif
  40 #ifndef TGNMLEN
  41 #define TGNMLEN 256
  42 #endif
  43
  44 static int saveuid = -993;
  45 static char saveuname[TUNMLEN];
  46 static int my_uid = -993;
  47
  48 static int savegid = -993;
  49 static char savegname[TGNMLEN];
  50 static int my_gid = -993;
  51
  52 #define myuid   ( my_uid < 0? (my_uid = getuid()): my_uid )
  53 #define mygid   ( my_gid < 0? (my_gid = getgid()): my_gid )
  54
  55 int
  56 finduid (char *uname)
  57 {
  58     struct passwd *pw;
  59
  60     if (uname[0] != saveuname[0]        /* Quick test w/o proc call */
  61         ||0 != strncmp (uname, saveuname, TUNMLEN)) {
  62         strncpy (saveuname, uname, TUNMLEN);
  63         pw = getpwnam (uname);
  64         if (pw) {
  65             saveuid = pw->pw_uid;
  66         } else {
  67             saveuid = myuid;
  68         }
  69     }
  70     return saveuid;
  71 }
  72
  73 int
  74 findgid (char *gname)
  75 {
  76     struct group *gr;
  77
  78     if (gname[0] != savegname[0]        /* Quick test w/o proc call */
  79         ||0 != strncmp (gname, savegname, TUNMLEN)) {
  80         strncpy (savegname, gname, TUNMLEN);
  81         gr = getgrnam (gname);
  82         if (gr) {
  83             savegid = gr->gr_gid;
  84         } else {
  85             savegid = mygid;
  86         }
  87     }
  88     return savegid;
  89 }