Update drift file at most once per hour

Instead of writing to the file on every reference update, update it
on first update, on exit and otherwise only once per hour.

diff --git a/reference.c b/reference.c
index df31420bfe39b89b8964103da58dce65929087eb..19cb8adbd7bab82744a2e9ca647e055ee4a2a7ea 100644 (file)
--- a/reference.c
+++ b/reference.c
@@ -76,6 +76,7 @@ static char *mail_change_user;
 
 /* Filename of the drift file. */
 static char *drift_file=NULL;
+static double drift_file_age;
 
 static void update_drift_file(double, double);
 
@@ -155,7 +156,7 @@ REF_Initialise(void)
           drift_file);
     }
 
-    update_drift_file(our_frequency_ppm,our_skew);
+    drift_file_age = 0.0;
   }
     
   LCL_SetAbsoluteFrequency(our_frequency_ppm);
@@ -201,6 +202,10 @@ REF_Finalise(void)
     LCL_SetLeap(0);
   }
 
+  if (drift_file && drift_file_age > 0.0) {
+    update_drift_file(LCL_ReadAbsoluteFrequency(), our_skew);
+  }
+
   Free(fb_drifts);
 
   initialised = 0;
@@ -531,6 +536,8 @@ REF_SetReference(int stratum,
 
   double abs_freq_ppm;
 
+  double update_interval;
+
   assert(initialised);
 
   /* Avoid getting NaNs */
@@ -630,21 +637,25 @@ REF_SetReference(int stratum,
             1.0e6*our_skew,
             our_offset);
 
+  UTI_DiffTimevalsToDouble(&update_interval, ref_time, &last_ref_update);
+
   if (drift_file) {
-    update_drift_file(abs_freq_ppm, our_skew);
+    /* Update drift file at most once per hour */
+    drift_file_age += update_interval;
+    if (drift_file_age < 0.0 || drift_file_age > 3600.0) {
+      update_drift_file(abs_freq_ppm, our_skew);
+      drift_file_age = 0.0;
+    }
   }
 
   /* Update fallback drifts */
   if (fb_drifts) {
-    double update_interval;
-
-    UTI_DiffTimevalsToDouble(&update_interval, ref_time, &last_ref_update);
-
     update_fb_drifts(abs_freq_ppm, update_interval);
-    last_ref_update = *ref_time;
-    last_ref_update_interval = update_interval;
   }
 
+  last_ref_update = *ref_time;
+  last_ref_update_interval = update_interval;
+
   /* And now set the freq and offset to zero */
   our_frequency = 0.0;
   our_offset = 0.0;