From: Florian Forster <octo@leeloo.lan.home.verplant.org>
Date: Sat, 17 Jan 2009 09:37:50 +0000 (+0100)
Subject: src/common.[ch]: Add `counter_diff', a function to calculate the difference of two... 
X-Git-Tag: collectd-4.6.0~105
X-Git-Url: https://git.octo.it/?a=commitdiff_plain;h=10b343057733ca75925de786f61cb7dfd58bacd5;p=collectd.git

src/common.[ch]: Add `counter_diff', a function to calculate the difference of two counters.

It's not just a simple (old - new), because wrap-around is handled, too.
---

diff --git a/src/common.c b/src/common.c
index ae89c44f..aeea28d3 100644
--- a/src/common.c
+++ b/src/common.c
@@ -925,4 +925,22 @@ int read_file_contents (const char *filename, char *buf, int bufsize)
 	return n;
 }
 
+counter_t counter_diff (counter_t old_value, counter_t new_value)
+{
+	counter_t diff;
+
+	if (old_value > new_value)
+	{
+		if (old_value <= 4294967295U)
+			diff = (4294967295U - old_value) + new_value;
+		else
+			diff = (18446744073709551615ULL - old_value)
+				+ new_value;
+	}
+	else
+	{
+		diff = new_value - old_value;
+	}
 
+	return (diff);
+} /* counter_t counter_to_gauge */
diff --git a/src/common.h b/src/common.h
index f463b77e..aefc2cc6 100644
--- a/src/common.h
+++ b/src/common.h
@@ -209,4 +209,6 @@ int walk_directory (const char *dir, dirwalk_callback_f callback,
 		void *user_data);
 int read_file_contents (const char *filename, char *buf, int bufsize);
 
+counter_t counter_diff (counter_t old_value, counter_t new_value);
+
 #endif /* COMMON_H */