Use proper 64-bit integer arithmetic for Hz calculation

The current code uses double floats, which makes no sense since
time differences are always integer and never fractional.

Also fix up the averaging code a bit.

This fixes some spurious wrong Hz values reported for
my Logitech Rumblepad 2.

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>

diff --git a/evhz.c b/evhz.c
index e515ce5415eeeda6bb46690d9185b29453d0db93..4fd770dadc8e30ce843c5f1b8fb585c5ff2686d2 100644 (file)
--- a/evhz.c
+++ b/evhz.c
@@ -27,7 +27,7 @@ typedef struct event_s {
     int hz[HZ_LIST];
     int count;
     int avghz;
-    double prev_time;
+    unsigned long long prev_time;
     char name[128];
 } event_t;
 
@@ -115,25 +115,32 @@ int main(int argc, char *argv[]) {
             }
 
             if(event.type == EV_REL || event.type == EV_ABS) {
-                double time;
-                int hz;
+                unsigned long long time, timediff;
+                unsigned hz = 0;
 
-                time = event.time.tv_sec * 1000 + event.time.tv_usec / 1000;
-                hz = 1000 / (time - events[i].prev_time);
+                time = (unsigned long long)event.time.tv_sec * 1000ULL;
+                time += (unsigned long long)event.time.tv_usec / 1000ULL;
+
+                timediff = time - events[i].prev_time;
+
+                if(timediff != 0)
+                    hz = 1000ULL / timediff;
 
                 if(hz > 0) {
-                    int j;
+                    unsigned j, maxavg;
 
                     events[i].count++;
                     events[i].hz[events[i].count & (HZ_LIST - 1)] = hz;
 
                     events[i].avghz = 0;
 
-                    for(j = 0; j < HZ_LIST; j++) {
+                    maxavg = (events[i].count > HZ_LIST) ? HZ_LIST : events[i].count;
+
+                    for(j = 0; j < maxavg; j++) {
                         events[i].avghz += events[i].hz[j];
                     }
 
-                    events[i].avghz /= (events[i].count > HZ_LIST) ? HZ_LIST : events[i].count;
+                    events[i].avghz /= maxavg;
 
                     if(verbose) printf("%s: Latest % 5iHz, Average % 5iHz\n", events[i].name, hz, events[i].avghz);
                 }