From 92fb929a296f08ae5907940baaee7a02db14dc8f Mon Sep 17 00:00:00 2001
From: simon <simon@cda61777-01e9-0310-a592-d414129be87e>
Date: Sun, 13 May 2012 15:59:27 +0000
Subject: [PATCH] Use clock_gettime(CLOCK_MONOTONIC) as the Unix getticks(), if
 it's available.

git-svn-id: svn://svn.tartarus.org/sgt/putty@9529 cda61777-01e9-0310-a592-d414129be87e
---
 unix/configure.ac |  2 ++
 unix/uxmisc.c     | 26 ++++++++++++++++++++------
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/unix/configure.ac b/unix/configure.ac
index a5185408..930f3e37 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -119,6 +119,8 @@ AC_CHECK_LIB(X11, XOpenDisplay,
               AC_DEFINE([HAVE_LIBX11],[],[Define if libX11.a is available])])
 
 AC_CHECK_FUNCS([getaddrinfo ptsname setresuid strsignal updwtmpx])
+AC_CHECK_DECLS([CLOCK_MONOTONIC], [], [], [[#include <time.h>]])
+AC_SEARCH_LIBS([clock_gettime], [rt], [AC_DEFINE([HAVE_CLOCK_GETTIME],[],[Define if clock_gettime() is available])])
 
 AC_OUTPUT
 
diff --git a/unix/uxmisc.c b/unix/uxmisc.c
index d11b2f74..01e1299d 100644
--- a/unix/uxmisc.c
+++ b/unix/uxmisc.c
@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <assert.h>
 #include <unistd.h>
+#include <time.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <pwd.h>
@@ -15,14 +16,27 @@
 
 unsigned long getticks(void)
 {
-    struct timeval tv;
-    gettimeofday(&tv, NULL);
     /*
-     * We want to use milliseconds rather than microseconds,
-     * because we need a decent number of them to fit into a 32-bit
-     * word so it can be used for keepalives.
+     * We want to use milliseconds rather than the microseconds or
+     * nanoseconds given by the underlying clock functions, because we
+     * need a decent number of them to fit into a 32-bit word so it
+     * can be used for keepalives.
      */
-    return tv.tv_sec * TICKSPERSEC + tv.tv_usec / (1000000 / TICKSPERSEC);
+#if defined HAVE_CLOCK_GETTIME && defined HAVE_DECL_CLOCK_MONOTONIC
+    {
+        /* Use CLOCK_MONOTONIC if available, so as to be unconfused if
+         * the system clock changes. */
+        struct timespec ts;
+        if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
+            return ts.tv_sec * TICKSPERSEC +
+                ts.tv_nsec / (1000000 / TICKSPERSEC);
+    }
+#endif
+    {
+        struct timeval tv;
+        gettimeofday(&tv, NULL);
+        return tv.tv_sec * TICKSPERSEC + tv.tv_usec / (1000000 / TICKSPERSEC);
+    }
 }
 
 Filename *filename_from_str(const char *str)
-- 
2.11.0