core: Add difference function to osmo_counter

The osmo_counter_difference returns the counter value difference
since the last call of this function with the given counter object.

Sponsored-by: On-Waves ehf

2 files changed, 12 insertions, 0 deletions

diff --git a/include/osmocom/core/statistics.h b/include/osmocom/core/statistics.h
index a9a623d3..1e472ffd 100644
--- a/include/osmocom/core/statistics.h
+++ b/include/osmocom/core/statistics.h
@@ -9,6 +9,7 @@ struct osmo_counter {
 	const char *name;		/*!< \brief human-readable name */
 	const char *description;	/*!< \brief humn-readable description */
 	unsigned long value;		/*!< \brief current value */
+	unsigned long previous;		/*!< \brief previous value */
 };
 
 /*! \brief Increment counter */
@@ -48,3 +49,6 @@ int osmo_counters_for_each(int (*handle_counter)(struct osmo_counter *, void *),
  *  \returns pointer to counter (\ref osmo_counter) or NULL otherwise
  */
 struct osmo_counter *osmo_counter_get_by_name(const char *name);
+
+/*! \brief Return the counter difference since the last call to this function */
+int osmo_counter_difference(struct osmo_counter *ctr);
diff --git a/src/statistics.c b/src/statistics.c
index e28541ba..ad069cea 100644
--- a/src/statistics.c
+++ b/src/statistics.c
@@ -74,3 +74,11 @@ struct osmo_counter *osmo_counter_get_by_name(const char *name)
 	}
 	return NULL;
 }
+
+int osmo_counter_difference(struct osmo_counter *ctr)
+{
+	int delta = ctr->value - ctr->previous;
+	ctr->previous = ctr->value;
+
+	return delta;
+}