R_API char *r_sys_getenv(const char *key) {
#if __WINDOWS__
	DWORD dwRet;
	LPTSTR envbuf = NULL, key_ = NULL, tmp_ptr;
	char *val = NULL;

	if (!key) {
		return NULL;
	}
	envbuf = (LPTSTR)malloc (sizeof (TCHAR) * TMP_BUFSIZE);
	if (!envbuf) {
		goto err_r_sys_get_env;
	}
	key_ = r_sys_conv_utf8_to_win (key);
	dwRet = GetEnvironmentVariable (key_, envbuf, TMP_BUFSIZE);
	if (dwRet == 0) {
		if (GetLastError () == ERROR_ENVVAR_NOT_FOUND) {
			goto err_r_sys_get_env;
		}
	} else if (TMP_BUFSIZE < dwRet) {
		tmp_ptr = (LPTSTR)realloc (envbuf, dwRet * sizeof (TCHAR));
		if (!tmp_ptr) {
			goto err_r_sys_get_env;
		}
		envbuf = tmp_ptr;
		dwRet = GetEnvironmentVariable (key_, envbuf, dwRet);
		if (!dwRet) {
			goto err_r_sys_get_env;
		}
	}
	val = r_sys_conv_win_to_utf8_l (envbuf, (int)dwRet);
err_r_sys_get_env:
	free (key_);
	free (envbuf);
	return val;
#else
	char *b;
	if (!key) {
		return NULL;
	}
	b = getenv (key);
	return b? strdup (b): NULL;
#endif
}