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/* Provide a working getlogin_r for systems which lack it.
Copyright (C) 2005-2007, 2010-2020 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert, Derek Price, and Bruno Haible. */
#include <config.h>
/* Specification. */
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include "malloca.h"
#if defined _WIN32 && ! defined __CYGWIN__
# define WIN32_LEAN_AND_MEAN
# include <windows.h>
/* Don't assume that UNICODE is not defined. */
# undef GetUserName
# define GetUserName GetUserNameA
#else
# if !HAVE_DECL_GETLOGIN
extern char *getlogin (void);
# endif
#endif
/* See unistd.in.h for documentation. */
int
getlogin_r (char *name, size_t size)
{
#undef getlogin_r
#if defined _WIN32 && ! defined __CYGWIN__
/* Native Windows platform. */
DWORD sz;
/* When size > 0x7fff, the doc says that GetUserName will fail.
Actually, on Windows XP SP3, it succeeds. But let's be safe,
for the sake of older Windows versions. */
if (size > 0x7fff)
size = 0x7fff;
sz = size;
if (!GetUserName (name, &sz))
{
if (GetLastError () == ERROR_INSUFFICIENT_BUFFER)
/* In this case, the doc says that sz contains the required size, but
actually, on Windows XP SP3, it contains 2 * the required size. */
return ERANGE;
else
return ENOENT;
}
return 0;
#elif HAVE_GETLOGIN_R
/* Platform with a getlogin_r() function. */
int ret = getlogin_r (name, size);
if (ret == 0)
{
const char *nul = memchr (name, '\0', size);
if (nul == NULL)
/* name contains a truncated result. */
return ERANGE;
if (size > 0 && nul == name + size - 1)
{
/* strlen(name) == size-1. Determine whether the untruncated result
would have had length size-1 or size. */
char *room = (char *) malloca (size + 1);
if (room == NULL)
return ENOMEM;
ret = getlogin_r (room, size + 1);
/* The untruncated result should be the same as in the first call. */
if (ret == 0 && memcmp (name, room, size) != 0)
/* The untruncated result would have been different. */
ret = ERANGE;
freea (room);
}
}
return ret;
#else
/* Platform with a getlogin() function. */
char *n;
size_t nlen;
errno = 0;
n = getlogin ();
if (!n)
/* ENOENT is a reasonable errno value if getlogin returns NULL. */
return (errno != 0 ? errno : ENOENT);
nlen = strlen (n);
if (size <= nlen)
return ERANGE;
memcpy (name, n, nlen + 1);
return 0;
#endif
}
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