cpu: implement int32 counter for PDH calls as well. (#1715)

internal/utils/counter.go

@@ -0,0 +1,23 @@
+package utils
+
+type Counter struct {
+	lastValue  uint32
+	totalValue float64
+}
+
+// NewCounter creates a new Counter that accepts uint32 values and returns float64 values.
+// It resolve the overflow issue of uint32 by using the difference between the last value and the current value.
+func NewCounter(lastValue uint32) Counter {
+	return Counter{
+		lastValue:  lastValue,
+		totalValue: 0,
+	}
+}
+
+func (c *Counter) AddValue(value uint32) {
+	c.totalValue += float64(value - c.lastValue)
+}
+
+func (c *Counter) Value() float64 {
+	return c.totalValue
+}

internal/utils/counter_test.go

@@ -0,0 +1,24 @@
+package utils_test
+
+import (
+	"math"
+	"testing"
+
+	"github.com/prometheus-community/windows_exporter/internal/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCounter(t *testing.T) {
+	t.Parallel()
+
+	c := utils.NewCounter(0)
+	assert.Equal(t, 0.0, c.Value()) //nolint:testifylint
+
+	c.AddValue(1)
+
+	assert.Equal(t, 1.0, c.Value()) //nolint:testifylint
+
+	c.AddValue(math.MaxUint32)
+
+	assert.Equal(t, float64(math.MaxUint32)+1.0, c.Value()) //nolint:testifylint
+}