1// Copyright 2020 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package metrics
6
7import (
8	"math"
9	"unsafe"
10)
11
12// ValueKind is a tag for a metric [Value] which indicates its type.
13type ValueKind int
14
15const (
16	// KindBad indicates that the Value has no type and should not be used.
17	KindBad ValueKind = iota
18
19	// KindUint64 indicates that the type of the Value is a uint64.
20	KindUint64
21
22	// KindFloat64 indicates that the type of the Value is a float64.
23	KindFloat64
24
25	// KindFloat64Histogram indicates that the type of the Value is a *Float64Histogram.
26	KindFloat64Histogram
27)
28
29// Value represents a metric value returned by the runtime.
30type Value struct {
31	kind    ValueKind
32	scalar  uint64         // contains scalar values for scalar Kinds.
33	pointer unsafe.Pointer // contains non-scalar values.
34}
35
36// Kind returns the tag representing the kind of value this is.
37func (v Value) Kind() ValueKind {
38	return v.kind
39}
40
41// Uint64 returns the internal uint64 value for the metric.
42//
43// If v.Kind() != KindUint64, this method panics.
44func (v Value) Uint64() uint64 {
45	if v.kind != KindUint64 {
46		panic("called Uint64 on non-uint64 metric value")
47	}
48	return v.scalar
49}
50
51// Float64 returns the internal float64 value for the metric.
52//
53// If v.Kind() != KindFloat64, this method panics.
54func (v Value) Float64() float64 {
55	if v.kind != KindFloat64 {
56		panic("called Float64 on non-float64 metric value")
57	}
58	return math.Float64frombits(v.scalar)
59}
60
61// Float64Histogram returns the internal *Float64Histogram value for the metric.
62//
63// If v.Kind() != KindFloat64Histogram, this method panics.
64func (v Value) Float64Histogram() *Float64Histogram {
65	if v.kind != KindFloat64Histogram {
66		panic("called Float64Histogram on non-Float64Histogram metric value")
67	}
68	return (*Float64Histogram)(v.pointer)
69}
70