From 6f76e100383189eb9fd2b861fe2cdba2d94b7c59 Mon Sep 17 00:00:00 2001
From: Klaus Schmidinger <vdr@tvdr.de>
Date: Thu, 27 Dec 2007 15:58:18 +0100
Subject: cTimeMs now uses the monotonic clock, if available

---
 tools.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

(limited to 'tools.c')

diff --git a/tools.c b/tools.c
index ba7b0cf9..2f8e0789 100644
--- a/tools.c
+++ b/tools.c
@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: tools.c 1.137 2007/11/03 15:34:07 kls Exp $
+ * $Id: tools.c 1.138 2007/12/27 15:57:49 kls Exp $
  */
 
 #include "tools.h"
@@ -545,6 +545,41 @@ cTimeMs::cTimeMs(int Ms)
 
 uint64_t cTimeMs::Now(void)
 {
+#if _POSIX_TIMERS > 0 && defined(_POSIX_MONOTONIC_CLOCK)
+#define MIN_RESOLUTION 5 // ms
+  static bool initialized = false;
+  static bool monotonic = false;
+  struct timespec tp;
+  if (!initialized) {
+     // check if monotonic timer is available and provides enough accurate resolution:
+     if (clock_getres(CLOCK_MONOTONIC, &tp) == 0) {
+        long Resolution = tp.tv_nsec;
+        // require a minimum resolution:
+        if (tp.tv_sec == 0 && tp.tv_nsec <= MIN_RESOLUTION * 1000000) {
+           if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0) {
+              dsyslog("cTimeMs: using monotonic clock (resolution is %ld ns)", Resolution);
+              monotonic = true;
+              }
+           else
+              esyslog("cTimeMs: clock_gettime(CLOCK_MONOTONIC) failed");
+           }
+        else
+           dsyslog("cTimeMs: not using monotonic clock - resolution is too bad (%ld s %ld ns)", tp.tv_sec, tp.tv_nsec);
+        }
+     else
+        esyslog("cTimeMs: clock_getres(CLOCK_MONOTONIC) failed");
+     initialized = true;
+     }
+  if (monotonic) {
+     if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0)
+        return (uint64_t(tp.tv_sec)) * 1000 + tp.tv_nsec / 1000000;
+     esyslog("cTimeMs: clock_gettime(CLOCK_MONOTONIC) failed");
+     monotonic = false;
+     // fall back to gettimeofday()
+     }
+#else
+#  warning Posix monotonic clock not available
+#endif
   struct timeval t;
   if (gettimeofday(&t, NULL) == 0)
      return (uint64_t(t.tv_sec)) * 1000 + t.tv_usec / 1000;
-- 
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