os: xhostname: helper for gethostname()

This little helper does the OS specific part for gethostname()
calls. It's putting the result into a fixed-length struct and making
sure it's properly filled and the string is always zero-terminated.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

os/meson.build

@@ -18,6 +18,7 @@ srcs_os = [
     'string.c',
     'utils.c',
     'xdmauth.c',
+    'xhostname.c',
     'xsha1.c',
     'xstrans.c',
     'xprintf.c',

os/xhostname.c

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: MIT OR X11
+ *
+ * Copyright © 2024 Enrico Weigelt, metux IT consult <info@metux.net>
+ */
+#include <dix-config.h>
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#if WIN32
+#include <winsock.h>
+#endif
+
+#include "os/xhostname.h"
+
+int xhostname(struct xhostname* hn)
+{
+    /* being extra-paranoid here */
+    memset(hn, 0, sizeof(struct xhostname));
+    int ret = gethostname(hn->name, sizeof(hn->name));
+
+    if (ret == -1) {
+        hn->name[0] = 0;
+        return errno;
+    }
+
+    hn->name[sizeof(hn->name)-1] = 0;
+    return ret;
+}

os/xhostname.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: MIT OR X11
+ *
+ * Copyright © 2024 Enrico Weigelt, metux IT consult <info@metux.net>
+ */
+#ifndef _XSERVER_OS_XHOSTNAME_H_
+#define _XSERVER_OS_XHOSTNAME_H_
+
+#define XHOSTNAME_MAX 2048
+
+struct xhostname {
+    char name[XHOSTNAME_MAX];
+};
+
+/*
+ * retrieve host's nodename. basically a safer way of gethostname() / uname()
+ * making sure that the nodename is always zero-terminated.
+ *
+ * @hn pointer to struct xhostname that will be filled
+ * @return 0 on success
+ */
+int xhostname(struct xhostname* hn);
+
+#endif /* _XSERVER_OS_XHOSTNAME_H_ */