// Copyright 2023 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 trace
import (
"fmt"
"unsafe"
)
// Value is a dynamically-typed value obtained from a trace.
type Value struct {
kind ValueKind
pointer unsafe.Pointer
scalar uint64
}
// ValueKind is the type of a dynamically-typed value from a trace.
type ValueKind uint8
const (
ValueBad ValueKind = iota
ValueUint64
ValueString
)
// Kind returns the ValueKind of the value.
//
// It represents the underlying structure of the value.
//
// New ValueKinds may be added in the future. Users of this type must be robust
// to that possibility.
func (v Value) Kind() ValueKind {
return v.kind
}
// Uint64 returns the uint64 value for a ValueUint64.
//
// Panics if this Value's Kind is not ValueUint64.
func (v Value) Uint64() uint64 {
if v.kind != ValueUint64 {
panic("Uint64 called on Value of a different Kind")
}
return v.scalar
}
// String returns the string value for a ValueString, and otherwise
// a string representation of the value for other kinds of values.
func (v Value) String() string {
if v.kind == ValueString {
return unsafe.String((*byte)(v.pointer), int(v.scalar))
}
switch v.kind {
case ValueUint64:
return fmt.Sprintf("Value{Uint64(%d)}", v.Uint64())
}
return "Value{Bad}"
}
func uint64Value(x uint64) Value {
return Value{kind: ValueUint64, scalar: x}
}
func stringValue(s string) Value {
return Value{kind: ValueString, scalar: uint64(len(s)), pointer: unsafe.Pointer(unsafe.StringData(s))}
}
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