include: add version_compare helper function

 Backported from X.org:

 commit 0df871cf34ee5f1a85586206027de9b02fb364ec
 Author: Robert Ancell <robert.ancell@canonical.com>
 Date:   Thu May 22 10:43:52 2014 +1200

    Fix overflow checking extension versions

    The easiest way to check for the version of an extension is to send the maximum
    possible version numbers in the QueryVersion request. The X server overflows on
    these as it assumes you will send a reasonable version number.

    Reviewed-by: Keith Packard <keithp@keithp.com>
    Signed-off-by: Keith Packard <keithp@keithp.com>

 commit ffd4874798ba54f86acac75779a15b4babeaa5f3
 Author: Peter Hutterer <peter.hutterer@who-t.net>
 Date:   Wed May 11 12:20:50 2011 +1000

    include: add version_compare helper function

    Compare two version numbers in the major.minor form.
    Switch the few users of manual version switching over to the new function.

    Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
    Reviewed-by: Jamey Sharp <jamey@minilop.net>

 Backport to nx-libs: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>

1 files changed, 23 insertions, 0 deletions

diff --git a/nx-X11/programs/Xserver/include/misc.h b/nx-X11/programs/Xserver/include/misc.h
index 5f30823fa..d2cadace2 100644
--- a/nx-X11/programs/Xserver/include/misc.h
+++ b/nx-X11/programs/Xserver/include/misc.h
@@ -81,6 +81,7 @@ extern unsigned long serverGeneration;
 #include <nx-X11/Xfuncproto.h>
 #include <nx-X11/Xmd.h>
 #include <nx-X11/X.h>
+#include <stdint.h>
 
 #ifndef _XTYPEDEF_POINTER
 /* Don't let Xdefs.h define 'pointer' */
@@ -237,6 +238,28 @@ pad_to_int32(const int bytes) {
     return (((bytes) + 3) & ~3);
 }
 
+/**
+ * Compare the two version numbers comprising of major.minor.
+ *
+ * @return A value less than 0 if a is less than b, 0 if a is equal to b,
+ * or a value greater than 0
+ */
+static inline int
+version_compare(uint32_t a_major, uint32_t a_minor,
+                uint32_t b_major, uint32_t b_minor)
+{
+    if (a_major > b_major)
+        return 1;
+    if (a_major < b_major)
+        return -1;
+    if (a_minor > b_minor)
+        return 1;
+    if (a_minor < b_minor)
+        return -1;
+
+    return 0;
+}
+
 /* some macros to help swap requests, replies, and events */
 
 #define LengthRestB(stuff) \