1 // Copyright 2023 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 5 package trace
6 7 import (
8 "fmt"
9 "unsafe"
10 )
11 12 // Value is a dynamically-typed value obtained from a trace.
13 type Value struct {
14 kind ValueKind
15 pointer unsafe.Pointer
16 scalar uint64
17 }
18 19 // ValueKind is the type of a dynamically-typed value from a trace.
20 type ValueKind uint8
21 22 const (
23 ValueBad ValueKind = iota
24 ValueUint64
25 ValueString
26 )
27 28 // Kind returns the ValueKind of the value.
29 //
30 // It represents the underlying structure of the value.
31 //
32 // New ValueKinds may be added in the future. Users of this type must be robust
33 // to that possibility.
34 func (v Value) Kind() ValueKind {
35 return v.kind
36 }
37 38 // Uint64 returns the uint64 value for a ValueUint64.
39 //
40 // Panics if this Value's Kind is not ValueUint64.
41 func (v Value) Uint64() uint64 {
42 if v.kind != ValueUint64 {
43 panic("Uint64 called on Value of a different Kind")
44 }
45 return v.scalar
46 }
47 48 // String returns the string value for a ValueString, and otherwise
49 // a string representation of the value for other kinds of values.
50 func (v Value) String() string {
51 if v.kind == ValueString {
52 return unsafe.String((*byte)(v.pointer), int(v.scalar))
53 }
54 switch v.kind {
55 case ValueUint64:
56 return fmt.Sprintf("Value{Uint64(%d)}", v.Uint64())
57 }
58 return "Value{Bad}"
59 }
60 61 func uint64Value(x uint64) Value {
62 return Value{kind: ValueUint64, scalar: x}
63 }
64 65 func stringValue(s []byte) Value {
66 return Value{kind: ValueString, scalar: uint64(len(s)), pointer: unsafe.Pointer(unsafe.StringData(s))}
67 }
68