From: Florian Forster <octo@leeloo.lan.home.verplant.org>
Date: Sun, 28 Oct 2007 16:48:29 +0000 (+0100)
Subject: src/utils_cache.c: Detect when a counter wraps around
X-Git-Tag: collectd-4.3.0beta0~128
X-Git-Url: https://git.octo.it/?a=commitdiff_plain;h=64765bc4d41af1af14e1fb90c4ae2b81d9de39b5;p=collectd.git

src/utils_cache.c: Detect when a counter wraps around

and calculate the difference correctly.
---

diff --git a/src/utils_cache.c b/src/utils_cache.c
index 5ecb83cf..79989a07 100644
--- a/src/utils_cache.c
+++ b/src/utils_cache.c
@@ -87,8 +87,24 @@ int uc_update (const data_set_t *ds, const value_list_t *vl)
     {
       if (ds->ds[i].type == DS_TYPE_COUNTER)
       {
-	ce->values_gauge[i] = ((double) (vl->values[i].counter
-	    - ce->values_counter[i]))
+	counter_t diff;
+
+	/* check if the counter has wrapped around */
+	if (vl->values[i].counter < ce->values_counter[i])
+	{
+	  if (ce->values_counter[i] <= 4294967295U)
+	    diff = (4294967295U - ce->values_counter[i])
+	      + vl->values[i].counter;
+	  else
+	    diff = (18446744073709551615ULL - ce->values_counter[i])
+	      + vl->values[i].counter;
+	}
+	else /* counter has NOT wrapped around */
+	{
+	  diff = vl->values[i].counter - ce->values_counter[i];
+	}
+
+	ce->values_gauge[i] = ((double) diff)
 	  / ((double) (vl->time - ce->last_update));
 	ce->values_counter[i] = vl->values[i].counter;
       }
diff --git a/src/utils_cache.h b/src/utils_cache.h
index 91454057..8d1c7549 100644
--- a/src/utils_cache.h
+++ b/src/utils_cache.h
@@ -1,5 +1,5 @@
 /**
- * collectd - src/utils_cache.c
+ * collectd - src/utils_cache.h
  * Copyright (C) 2007  Florian octo Forster
  *
  * This program is free software; you can redistribute it and/or modify it