1 files changed, 69 insertions, 0 deletions
diff --git a/src/runtime/metrics/value.go b/src/runtime/metrics/value.go
new file mode 100644
index 0000000000..0b056b4ea8
--- /dev/null
+++ b/src/runtime/metrics/value.go
@@ -0,0 +1,69 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package metrics
+
+import (
+	"math"
+	"unsafe"
+)
+
+// ValueKind is a tag for a metric Value which indicates its type.
+type ValueKind int
+
+const (
+	// KindBad indicates that the Value has no type and should not be used.
+	KindBad ValueKind = iota
+
+	// KindUint64 indicates that the type of the Value is a uint64.
+	KindUint64
+
+	// KindFloat64 indicates that the type of the Value is a float64.
+	KindFloat64
+
+	// KindFloat64Histogram indicates that the type of the Value is a *Float64Histogram.
+	KindFloat64Histogram
+)
+
+// Value represents a metric value returned by the runtime.
+type Value struct {
+	kind    ValueKind
+	scalar  uint64         // contains scalar values for scalar Kinds.
+	pointer unsafe.Pointer // contains non-scalar values.
+}
+
+// Kind returns the a tag representing the kind of value this is.
+func (v Value) Kind() ValueKind {
+	return v.kind
+}
+
+// Uint64 returns the internal uint64 value for the metric.
+//
+// If v.Kind() != KindUint64, this method panics.
+func (v Value) Uint64() uint64 {
+	if v.kind != KindUint64 {
+		panic("called Uint64 on non-uint64 metric value")
+	}
+	return v.scalar
+}
+
+// Float64 returns the internal float64 value for the metric.
+//
+// If v.Kind() != KindFloat64, this method panics.
+func (v Value) Float64() float64 {
+	if v.kind != KindFloat64 {
+		panic("called Float64 on non-float64 metric value")
+	}
+	return math.Float64frombits(v.scalar)
+}
+
+// Float64Histogram returns the internal *Float64Histogram value for the metric.
+//
+// If v.Kind() != KindFloat64Histogram, this method panics.
+func (v Value) Float64Histogram() *Float64Histogram {
+	if v.kind != KindFloat64Histogram {
+		panic("called Float64 on non-float64 metric value")
+	}
+	return (*Float64Histogram)(v.pointer)
+}