[gpsd-dev] [PATCH 3/3] Print offset in ntpshmmon instead of reference time

[Miroslav Lichvar]

---
 contrib/ntpshmviz |  4 ++--
 ntpshmmon.c       | 11 +++++++----
 ntpshmmon.xml     | 28 +++++++++++++---------------
 3 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/contrib/ntpshmviz b/contrib/ntpshmviz
index 17c754d..9152819 100755
--- a/contrib/ntpshmviz
+++ b/contrib/ntpshmviz
@@ -110,7 +110,7 @@ class ntpOffset:
         #   - The NTP unit from which it was collected.
         #   - Collection time of day, expressed in seconds
         #   - Receiver time of day, expressed in seconds
-        #   - Clock time of day, expressed in seconds
+        #   - Offset, expressed in seconds
         #   - Leep-second notification status
         #   - Source precision (log(2) of source jitter)
 
@@ -128,7 +128,7 @@ class ntpOffset:
                 if line[:1] != '#':
                     line = line.lstrip()
                     record = line.split(' ')
-                    offset = (float(record[3]) - float(record[4]))
+                    offset = float(record[4])
 
                     # If the NTP unit is in the dictionary
                     # append the offset to the list
diff --git a/ntpshmmon.c b/ntpshmmon.c
index c2a621c..07d3c32 100644
--- a/ntpshmmon.c
+++ b/ntpshmmon.c
@@ -21,6 +21,9 @@
 /* WARNING!  this will overflow if x and y differ by more than a few seconds */
 #define timespec_diff_ns(x, y) 
(long)(((x).tv_sec-(y).tv_sec)*1000000000+(x).tv_nsec-(y).tv_nsec)
 
+/* difference between timestamps as a double */
+#define timespec_diff_dbl(x, y)        
(((x).tv_sec-(y).tv_sec)+1e-9*((x).tv_nsec-(y).tv_nsec))
+
 static struct shmTime *segments[NTPSEGMENTS + 1];
 static struct timespec tick[NTPSEGMENTS + 1];
 
@@ -79,8 +82,8 @@ int main(int argc, char **argv)
        exit(EXIT_SUCCESS);
     }
 
-    (void)printf("ntpshmmon version 1\n");
-    (void)printf("#      Name   Seen@                Clock                Real 
              L Prec\n");
+    (void)printf("ntpshmmon version 2\n");
+    (void)printf("#      Name   Seen@                Received@            
Offset             L Prec\n");
 
     do {
        struct shm_stat_t       shm_stat;
@@ -93,11 +96,11 @@ int main(int argc, char **argv)
            {
            case OK:
                if (timespec_diff_ns(shm_stat.tvc, tick[i]) >= cycle * 
1000000000) {
-                   printf("sample %s %ld.%09ld %ld.%09ld %ld.%09ld %d %3d\n",
+                   printf("sample %s %ld.%09ld %ld.%09ld %+020.9f %d %3d\n",
                           ntp_name(i),
                           (long)shm_stat.tvc.tv_sec, shm_stat.tvc.tv_nsec,
                           (long)shm_stat.tvr.tv_sec, shm_stat.tvr.tv_nsec,
-                          (long)shm_stat.tvt.tv_sec, shm_stat.tvt.tv_nsec,
+                          timespec_diff_dbl(shm_stat.tvt, shm_stat.tvr),
                           shm_stat.leap, shm_stat.precision);
                    tick[i] = shm_stat.tvc;
                    --nsamples;
diff --git a/ntpshmmon.xml b/ntpshmmon.xml
index 82e1bd0..498d70d 100644
--- a/ntpshmmon.xml
+++ b/ntpshmmon.xml
@@ -49,15 +49,14 @@ fields.</para>
 <para>Here is an example of the beginning of a report file:
 
 <literallayout>
-ntpshmmon version 1
-#      Name   Seen@                Clock                Real               L 
Prec
-sample NTP2 1424926256.443030206 1424926256.115869233 1424926256.000000000 0  
-1
-sample NTP3 1424926256.443060517 1424926255.995430821 1424926256.000000000 0 
-20
-sample NTP3 1424926256.995747347 1424926256.995422728 1424926257.000000000 0 
-20
-sample NTP2 1424926257.112433572 1424926257.111936726 1424926257.000000000 0  
-1
-sample NTP3 1424926257.996221153 1424926257.995410232 1424926258.000000000 0 
-20
-sample NTP2 1424926258.107769409 1424926258.107451006 1424926258.000000000 0  
-1
-sample NTP3 1424926258.995647636 1424926258.995406476 1424926259.000000000 0 
-20
+ntpshmmon version 2
+#      Name   Seen@                Received@            Offset             L 
Prec
+sample NTP1 1430993523.879335377 1430993522.999999050 +000000000.000000950 0 
-20
+sample NTP0 1430993524.435727285 1430993524.434913144 -000000000.434913144 0  
-1
+sample NTP1 1430993524.880300614 1430993524.000001746 -000000000.000001746 0 
-20
+sample NTP0 1430993525.437669569 1430993525.437044263 -000000000.437044263 0  
-1
+sample NTP1 1430993525.881070289 1430993525.000000172 -000000000.000000172 0 
-20
+sample NTP0 1430993526.438515249 1430993526.430013058 -000000000.430013058 0  
-1
 </literallayout></para>
 
 <para>The output always begins with a header line expressing the
@@ -80,7 +79,7 @@ itself.</para>
 
 <listitem><para>Receiver time of day, seconds.</para></listitem>
 
-<listitem><para>Clock time of day, seconds.</para></listitem>
+<listitem><para>Offset betweeen reference time and receiver time, 
seconds.</para></listitem>
 
 <listitem><para>Leap-second notification status.</para></listitem>
 
@@ -88,11 +87,10 @@ itself.</para>
 </orderedlist>
 </para>
 
-<para>In these fields, "clock time" is the high-precision time
-measured by the source and "receiver time" is Unix UTC time at the
-receiver. It is normal for the seconds part of receiver time to
-coincide with the seconds part of collection time and for the
-nanoseconds part of receiver time to be zero.</para>
+<para>In these fields, "receiver time" is Unix UTC time when was the reference
+time received. It is normal for the seconds part of receiver time to
+coincide with the seconds part of collection time. The offset should be close
+to zero when the clock is synchronized.</para>
 
 <variablelist>
 <varlistentry>
-- 
2.1.0