From 866e1b2741ec958e18334094e2770059b710d11e Mon Sep 17 00:00:00 2001
From: Pierre-Yves Ritschard <pyr@spootnik.org>
Date: Thu, 16 Jan 2014 19:23:52 +0100
Subject: [PATCH] add a value_to_rate function.

---
 src/common.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 src/common.h | 10 +++++++++
 2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/src/common.c b/src/common.c
index 81142fd0..18b5c432 100644
--- a/src/common.c
+++ b/src/common.c
@@ -650,7 +650,7 @@ int get_kstat (kstat_t **ksp_ptr, char *module, int instance, char *name)
 	char ident[128];
 
 	*ksp_ptr = NULL;
-	
+
 	if (kc == NULL)
 		return (-1);
 
@@ -1236,7 +1236,7 @@ int walk_directory (const char *dir, dirwalk_callback_f callback,
 	while ((ent = readdir (dh)) != NULL)
 	{
 		int status;
-		
+
 		if (include_hidden)
 		{
 			if ((strcmp (".", ent->d_name) == 0)
@@ -1399,6 +1399,69 @@ int rate_to_value (value_t *ret_value, gauge_t rate, /* {{{ */
 	return (0);
 } /* }}} value_t rate_to_value */
 
+int value_to_rate (value_t *ret_rate, derive_t value, /* {{{ */
+		value_to_rate_state_t *state,
+		int ds_type, cdtime_t t)
+{
+	double interval;
+
+	/* Another invalid state: The time is not increasing. */
+	if (t <= state->last_time)
+	{
+		memset (state, 0, sizeof (*state));
+		return (EINVAL);
+	}
+
+	interval = CDTIME_T_TO_DOUBLE(t - state->last_time);
+
+	/* Previous value is invalid. */
+	if (state->last_time == 0) /* {{{ */
+	{
+		if (ds_type == DS_TYPE_DERIVE)
+		{
+			state->last_value.derive = value;
+		}
+		else if (ds_type == DS_TYPE_COUNTER)
+		{
+			state->last_value.counter = (counter_t) value;
+		}
+		else if (ds_type == DS_TYPE_ABSOLUTE)
+		{
+			state->last_value.absolute = (absolute_t) value;
+		}
+		else
+		{
+			assert (23 == 42);
+		}
+
+		state->last_time = t;
+		return (EAGAIN);
+	} /* }}} */
+
+	if (ds_type == DS_TYPE_DERIVE)
+	{
+		ret_rate->gauge = (value - state->last_value.derive) / interval;
+		state->last_value.derive = value;
+	}
+	else if (ds_type == DS_TYPE_COUNTER)
+	{
+		ret_rate->gauge = (((counter_t)value) - state->last_value.counter) / interval;
+		state->last_value.counter = (counter_t) value;
+	}
+	else if (ds_type == DS_TYPE_ABSOLUTE)
+	{
+		ret_rate->gauge = (((absolute_t)value) - state->last_value.absolute) / interval;
+		state->last_value.absolute = (absolute_t) value;
+	}
+	else
+	{
+		assert (23 == 42);
+	}
+
+        state->last_time = t;
+	return (0);
+} /* }}} value_t rate_to_value */
+
 int service_name_to_port_number (const char *service_name)
 {
 	struct addrinfo *ai_list;
diff --git a/src/common.h b/src/common.h
index 67f307c3..29590ff2 100644
--- a/src/common.h
+++ b/src/common.h
@@ -55,6 +55,13 @@ struct rate_to_value_state_s
 };
 typedef struct rate_to_value_state_s rate_to_value_state_t;
 
+struct value_to_rate_state_s
+{
+  value_t last_value;
+  cdtime_t last_time;
+};
+typedef struct value_to_rate_state_s value_to_rate_state_t;
+
 char *sstrncpy (char *dest, const char *src, size_t n);
 
 __attribute__ ((format(printf,3,4)))
@@ -324,6 +331,9 @@ counter_t counter_diff (counter_t old_value, counter_t new_value);
 int rate_to_value (value_t *ret_value, gauge_t rate,
 		rate_to_value_state_t *state, int ds_type, cdtime_t t);
 
+int value_to_rate (value_t *ret_rate, derive_t value,
+		value_to_rate_state_t *state, int ds_type, cdtime_t t);
+
 /* Converts a service name (a string) to a port number
  * (in the range [1-65535]). Returns less than zero on error. */
 int service_name_to_port_number (const char *service_name);
-- 
2.11.0