Add vendoring

vendor/github.com/VictoriaMetrics/metrics/gauge.go

@@ -0,0 +1,122 @@
+package metrics
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"sync/atomic"
+)
+
+// NewGauge registers and returns gauge with the given name, which calls f to obtain gauge value.
+//
+// name must be valid Prometheus-compatible metric with possible labels.
+// For instance,
+//
+//   - foo
+//   - foo{bar="baz"}
+//   - foo{bar="baz",aaa="b"}
+//
+// f must be safe for concurrent calls.
+// if f is nil, then it is expected that the gauge value is changed via Set(), Inc(), Dec() and Add() calls.
+//
+// The returned gauge is safe to use from concurrent goroutines.
+//
+// See also FloatCounter for working with floating-point values.
+func NewGauge(name string, f func() float64) *Gauge {
+	return defaultSet.NewGauge(name, f)
+}
+
+// Gauge is a float64 gauge.
+type Gauge struct {
+	// valueBits contains uint64 representation of float64 passed to Gauge.Set.
+	valueBits uint64
+
+	// f is a callback, which is called for returning the gauge value.
+	f func() float64
+}
+
+// Get returns the current value for g.
+func (g *Gauge) Get() float64 {
+	if f := g.f; f != nil {
+		return f()
+	}
+	n := atomic.LoadUint64(&g.valueBits)
+	return math.Float64frombits(n)
+}
+
+// Set sets g value to v.
+//
+// The g must be created with nil callback in order to be able to call this function.
+func (g *Gauge) Set(v float64) {
+	if g.f != nil {
+		panic(fmt.Errorf("cannot call Set on gauge created with non-nil callback"))
+	}
+	n := math.Float64bits(v)
+	atomic.StoreUint64(&g.valueBits, n)
+}
+
+// Inc increments g by 1.
+//
+// The g must be created with nil callback in order to be able to call this function.
+func (g *Gauge) Inc() {
+	g.Add(1)
+}
+
+// Dec decrements g by 1.
+//
+// The g must be created with nil callback in order to be able to call this function.
+func (g *Gauge) Dec() {
+	g.Add(-1)
+}
+
+// Add adds fAdd to g. fAdd may be positive and negative.
+//
+// The g must be created with nil callback in order to be able to call this function.
+func (g *Gauge) Add(fAdd float64) {
+	if g.f != nil {
+		panic(fmt.Errorf("cannot call Set on gauge created with non-nil callback"))
+	}
+	for {
+		n := atomic.LoadUint64(&g.valueBits)
+		f := math.Float64frombits(n)
+		fNew := f + fAdd
+		nNew := math.Float64bits(fNew)
+		if atomic.CompareAndSwapUint64(&g.valueBits, n, nNew) {
+			break
+		}
+	}
+}
+
+func (g *Gauge) marshalTo(prefix string, w io.Writer) {
+	v := g.Get()
+	if float64(int64(v)) == v {
+		// Marshal integer values without scientific notation
+		fmt.Fprintf(w, "%s %d\n", prefix, int64(v))
+	} else {
+		fmt.Fprintf(w, "%s %g\n", prefix, v)
+	}
+}
+
+func (g *Gauge) metricType() string {
+	return "gauge"
+}
+
+// GetOrCreateGauge returns registered gauge with the given name
+// or creates new gauge if the registry doesn't contain gauge with
+// the given name.
+//
+// name must be valid Prometheus-compatible metric with possible labels.
+// For instance,
+//
+//   - foo
+//   - foo{bar="baz"}
+//   - foo{bar="baz",aaa="b"}
+//
+// The returned gauge is safe to use from concurrent goroutines.
+//
+// Performance tip: prefer NewGauge instead of GetOrCreateGauge.
+//
+// See also FloatCounter for working with floating-point values.
+func GetOrCreateGauge(name string, f func() float64) *Gauge {
+	return defaultSet.GetOrCreateGauge(name, f)
+}