gnulib/import/getlogin_r.c

   1 /* Provide a working getlogin_r for systems which lack it.
   2
   3    Copyright (C) 2005-2007, 2010-2016 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert, Derek Price, and Bruno Haible.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <unistd.h>
  24
  25 #include <errno.h>
  26 #include <string.h>
  27
  28 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  29 # define WIN32_LEAN_AND_MEAN
  30 # include <windows.h>
  31 #else
  32 # if !HAVE_DECL_GETLOGIN
  33 extern char *getlogin (void);
  34 # endif
  35 #endif
  36
  37 /* See unistd.in.h for documentation.  */
  38 int
  39 getlogin_r (char *name, size_t size)
  40 {
  41 #undef getlogin_r
  42 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  43   /* Native Windows platform.  */
  44   DWORD sz;
  45
  46   /* When size > 0x7fff, the doc says that GetUserName will fail.
  47      Actually, on Windows XP SP3, it succeeds.  But let's be safe,
  48      for the sake of older Windows versions.  */
  49   if (size > 0x7fff)
  50     size = 0x7fff;
  51   sz = size;
  52   if (!GetUserName (name, &sz))
  53     {
  54       if (GetLastError () == ERROR_INSUFFICIENT_BUFFER)
  55         /* In this case, the doc says that sz contains the required size, but
  56            actually, on Windows XP SP3, it contains 2 * the required size.  */
  57         return ERANGE;
  58       else
  59         return ENOENT;
  60     }
  61   return 0;
  62 #elif HAVE_GETLOGIN_R
  63   /* Platform with a getlogin_r() function.  */
  64   int ret = getlogin_r (name, size);
  65
  66   if (ret == 0 && memchr (name, '\0', size) == NULL)
  67     /* name contains a truncated result.  */
  68     return ERANGE;
  69   return ret;
  70 #else
  71   /* Platform with a getlogin() function.  */
  72   char *n;
  73   size_t nlen;
  74
  75   errno = 0;
  76   n = getlogin ();
  77   if (!n)
  78     /* ENOENT is a reasonable errno value if getlogin returns NULL.  */
  79     return (errno != 0 ? errno : ENOENT);
  80
  81   nlen = strlen (n);
  82   if (size <= nlen)
  83     return ERANGE;
  84   memcpy (name, n, nlen + 1);
  85   return 0;
  86 #endif
  87 }