Added ndpi_data_jitter() API call

Author: lucaderi

src/include/ndpi_api.h

@@ -1728,6 +1728,7 @@ extern "C" {
   float ndpi_data_variance(struct ndpi_analyze_struct *s);
   float ndpi_data_stddev(struct ndpi_analyze_struct *s);
   float ndpi_data_mean(struct ndpi_analyze_struct *s);
+  float ndpi_data_jitter(struct ndpi_analyze_struct *s);
   u_int64_t ndpi_data_last(struct ndpi_analyze_struct *s);
   u_int64_t ndpi_data_min(struct ndpi_analyze_struct *s);
   u_int64_t ndpi_data_max(struct ndpi_analyze_struct *s);

src/include/ndpi_typedefs.h

@@ -1760,7 +1760,7 @@ typedef struct {
 
 struct ndpi_analyze_struct {
   u_int64_t *values;
-  u_int64_t min_val, max_val, sum_total;
+  u_int64_t min_val, max_val, sum_total, jitter_total;
   u_int32_t num_data_entries, next_value_insert_index;
   u_int16_t num_values_array_len /* length of the values array */;
 

src/lib/ndpi_analyze.c

@@ -116,6 +116,12 @@ void ndpi_data_add_value(struct ndpi_analyze_struct *s, const u_int64_t value) {
   if(!s)
     return;
 
+  if(s->num_data_entries > 0) {
+    u_int64_t last = ndpi_data_last(s);
+    
+    s->jitter_total += (last > value) ? (last - value) : (value - last);
+  }
+  
   if(s->sum_total == 0)
     s->min_val = s->max_val = value;
   else {
@@ -205,6 +211,15 @@ float ndpi_data_mean(struct ndpi_analyze_struct *s) {
 
 /* ********************************************************************************* */
 
+float ndpi_data_jitter(struct ndpi_analyze_struct *s) {
+  if(s->num_data_entries < 2)
+    return(0);
+  else
+    return((float)s->jitter_total / (float)(s->num_data_entries - 1));
+}
+
+/* ********************************************************************************* */
+
 /* Compute the average only on the sliding window */
 float ndpi_data_window_average(struct ndpi_analyze_struct *s) {
   if(s && s->num_values_array_len) {