core: Extend rate_ctr by helper functions

For global value reporting, some additional helper functions are
needed. The statsd protocol expects differential counter values,
which are currently not provided by rate_ctr (except for s/m/h/d
intervals).

This commit adds several helper functions to rate_ctr:

- rate_ctr_difference  returns the counter delta since the last
                       call to this function for a given counter
- rate_ctr_for_each_counter
                       iterates through each counter of a group
- rate_ctr_for_each_group
                       iterates through all globally registered
                       counter groups

Note that the rate_ctr_difference function can only be used by a
single backend, since it modifies the 'previous' field in the
rate_ctr obj.

Sponsored-by: On-Waves ehf

include/osmocom/core/rate_ctr.h

@@ -30,6 +30,7 @@ struct rate_ctr_per_intv {
 /*! \brief data we keep for each actual value */
 struct rate_ctr {
 	uint64_t current;	/*!< \brief current value */
+	uint64_t previous;	/*!< \brief previous value, used for delta */
 	/*! \brief per-interval data */
 	struct rate_ctr_per_intv intv[RATE_CTR_INTV_NUM];
 };
@@ -78,9 +79,27 @@ static inline void rate_ctr_inc(struct rate_ctr *ctr)
 	rate_ctr_add(ctr, 1);
 }
 
+/*! \brief Return the counter difference since the last call to this function */
+int64_t rate_ctr_difference(struct rate_ctr *ctr);
+
 int rate_ctr_init(void *tall_ctx);
 
 struct rate_ctr_group *rate_ctr_get_group_by_name_idx(const char *name, const unsigned int idx);
 const struct rate_ctr *rate_ctr_get_by_name(const struct rate_ctr_group *ctrg, const char *name);
 
+typedef int (*rate_ctr_handler_t)(
+	struct rate_ctr_group *, struct rate_ctr *,
+	const struct rate_ctr_desc *, void *);
+typedef int (*rate_ctr_group_handler_t)(struct rate_ctr_group *, void *);
+
+
+/*! \brief Iterate over all counters
+ *  \param[in] handle_item Call-back function, aborts if rc < 0
+ *  \param[in] data Private data handed through to \a handle_counter
+ */
+int rate_ctr_for_each_counter(struct rate_ctr_group *ctrg,
+	rate_ctr_handler_t handle_counter, void *data);
+
+int rate_ctr_for_each_group(rate_ctr_group_handler_t handle_group, void *data);
+
 /*! @} */

src/rate_ctr.c

@@ -83,6 +83,15 @@ void rate_ctr_add(struct rate_ctr *ctr, int inc)
 	ctr->current += inc;
 }
 
+/*! \brief Return the counter difference since the last call to this function */
+int64_t rate_ctr_difference(struct rate_ctr *ctr)
+{
+	int64_t result = ctr->current - ctr->previous;
+	ctr->previous = ctr->current;
+
+	return result;
+}
+
 static void interval_expired(struct rate_ctr *ctr, enum rate_ctr_intv intv)
 {
 	/* calculate rate over last interval */
@@ -177,4 +186,36 @@ const struct rate_ctr *rate_ctr_get_by_name(const struct rate_ctr_group *ctrg, c
 	return NULL;
 }
 
+int rate_ctr_for_each_counter(struct rate_ctr_group *ctrg,
+	rate_ctr_handler_t handle_counter, void *data)
+{
+	int rc = 0;
+	int i;
+
+	for (i = 0; i < ctrg->desc->num_ctr; i++) {
+		struct rate_ctr *ctr = &ctrg->ctr[i];
+		rc = handle_counter(ctrg,
+			ctr, &ctrg->desc->ctr_desc[i], data);
+		if (rc < 0)
+			return rc;
+	}
+
+	return rc;
+}
+
+int rate_ctr_for_each_group(rate_ctr_group_handler_t handle_group, void *data)
+{
+	struct rate_ctr_group *statg;
+	int rc = 0;
+
+	llist_for_each_entry(statg, &rate_ctr_groups, list) {
+		rc = handle_group(statg, data);
+		if (rc < 0)
+			return rc;
+	}
+
+	return rc;
+}
+
+
 /*! @} */