testing/protopack/pack.go - protobuf - Git at Google

 // Copyright 2018 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 protopack enables manual encoding and decoding of protobuf wire data.
 //
 // This package is intended for use in debugging and/or creation of test data.
 // Proper usage of this package requires knowledge of the wire format.
 //
 // See https://protobuf.dev/programming-guides/encoding.
 package protopack

 import (
 	"fmt"
 	"io"
 	"math"
 	"path"
 	"reflect"
 	"strconv"
 	"strings"
 	"unicode"
 	"unicode/utf8"

 	"google.golang.org/protobuf/encoding/protowire"
 	"google.golang.org/protobuf/reflect/protoreflect"
 )

 // Number is the field number; aliased from the [protowire] package for convenience.
 type Number = protowire.Number

 // Number type constants; copied from the [protowire] package for convenience.
 const (
 	MinValidNumber      Number = protowire.MinValidNumber
 	FirstReservedNumber Number = protowire.FirstReservedNumber
 	LastReservedNumber  Number = protowire.LastReservedNumber
 	MaxValidNumber      Number = protowire.MaxValidNumber
 )

 // Type is the wire type; aliased from the [protowire] package for convenience.
 type Type = protowire.Type

 // Wire type constants; copied from the [protowire] package for convenience.
 const (
 	VarintType     Type = protowire.VarintType
 	Fixed32Type    Type = protowire.Fixed32Type
 	Fixed64Type    Type = protowire.Fixed64Type
 	BytesType      Type = protowire.BytesType
 	StartGroupType Type = protowire.StartGroupType
 	EndGroupType   Type = protowire.EndGroupType
 )

 type (
 	// Token is any other type (e.g., [Message], [Tag], [Varint], [Float32], etc).
 	Token token
 	// Message is an ordered sequence of [Token] values, where certain tokens may
 	// contain other tokens. It is functionally a concrete syntax tree that
 	// losslessly represents any arbitrary wire data (including invalid input).
 	Message []Token

 	// Tag is a tuple of the field number and the wire type.
 	Tag struct {
 		Number Number
 		Type   Type
 	}
 	// Bool is a boolean.
 	Bool bool
 	// Varint is a signed varint using 64-bit two's complement encoding.
 	Varint int64
 	// Svarint is a signed varint using zig-zag encoding.
 	Svarint int64
 	// Uvarint is a unsigned varint.
 	Uvarint uint64

 	// Int32 is a signed 32-bit fixed-width integer.
 	Int32 int32
 	// Uint32 is an unsigned 32-bit fixed-width integer.
 	Uint32 uint32
 	// Float32 is a 32-bit fixed-width floating point number.
 	Float32 float32

 	// Int64 is a signed 64-bit fixed-width integer.
 	Int64 int64
 	// Uint64 is an unsigned 64-bit fixed-width integer.
 	Uint64 uint64
 	// Float64 is a 64-bit fixed-width floating point number.
 	Float64 float64

 	// String is a length-prefixed string.
 	String string
 	// Bytes is a length-prefixed bytes.
 	Bytes []byte
 	// LengthPrefix is a length-prefixed message.
 	LengthPrefix Message

 	// Denormalized is a denormalized varint value, where a varint is encoded
 	// using more bytes than is strictly necessary. The number of extra bytes
 	// alone is sufficient to losslessly represent the denormalized varint.
 	//
 	// The value may be one of [Tag], [Bool], [Varint], [Svarint], or [Uvarint],
 	// where the varint representation of each token is denormalized.
 	//
 	// Alternatively, the value may be one of [String], [Bytes], or [LengthPrefix],
 	// where the varint representation of the length-prefix is denormalized.
 	Denormalized struct {
 		Count uint // number of extra bytes
 		Value Token
 	}

 	// Raw are bytes directly appended to output.
 	Raw []byte
 )

 type token interface {
 	isToken()
 }

 func (Message) isToken()      {}
 func (Tag) isToken()          {}
 func (Bool) isToken()         {}
 func (Varint) isToken()       {}
 func (Svarint) isToken()      {}
 func (Uvarint) isToken()      {}
 func (Int32) isToken()        {}
 func (Uint32) isToken()       {}
 func (Float32) isToken()      {}
 func (Int64) isToken()        {}
 func (Uint64) isToken()       {}
 func (Float64) isToken()      {}
 func (String) isToken()       {}
 func (Bytes) isToken()        {}
 func (LengthPrefix) isToken() {}
 func (Denormalized) isToken() {}
 func (Raw) isToken()          {}

 // Size reports the size in bytes of the marshaled message.
 func (m Message) Size() int {
 	var n int
 	for _, v := range m {
 		switch v := v.(type) {
 		case Message:
 			n += v.Size()
 		case Tag:
 			n += protowire.SizeTag(v.Number)
 		case Bool:
 			n += protowire.SizeVarint(protowire.EncodeBool(false))
 		case Varint:
 			n += protowire.SizeVarint(uint64(v))
 		case Svarint:
 			n += protowire.SizeVarint(protowire.EncodeZigZag(int64(v)))
 		case Uvarint:
 			n += protowire.SizeVarint(uint64(v))
 		case Int32, Uint32, Float32:
 			n += protowire.SizeFixed32()
 		case Int64, Uint64, Float64:
 			n += protowire.SizeFixed64()
 		case String:
 			n += protowire.SizeBytes(len(v))
 		case Bytes:
 			n += protowire.SizeBytes(len(v))
 		case LengthPrefix:
 			n += protowire.SizeBytes(Message(v).Size())
 		case Denormalized:
 			n += int(v.Count) + Message{v.Value}.Size()
 		case Raw:
 			n += len(v)
 		default:
 			panic(fmt.Sprintf("unknown type: %T", v))
 		}
 	}
 	return n
 }

 // Marshal encodes a syntax tree into the protobuf wire format.
 //
 // Example message definition:
 //
 //	message MyMessage {
 //		string field1 = 1;
 //		int64 field2 = 2;
 //		repeated float32 field3 = 3;
 //	}
 //
 // Example encoded message:
 //
 //	b := Message{
 //		Tag{1, BytesType}, String("Hello, world!"),
 //		Tag{2, VarintType}, Varint(-10),
 //		Tag{3, BytesType}, LengthPrefix{
 //			Float32(1.1), Float32(2.2), Float32(3.3),
 //		},
 //	}.Marshal()
 //
 // Resulting wire data:
 //
 //	0x0000  0a 0d 48 65 6c 6c 6f 2c  20 77 6f 72 6c 64 21 10  |..Hello, world!.|
 //	0x0010  f6 ff ff ff ff ff ff ff  ff 01 1a 0c cd cc 8c 3f  |...............?|
 //	0x0020  cd cc 0c 40 33 33 53 40                           |...@33S@|
 func (m Message) Marshal() []byte {
 	var out []byte
 	for _, v := range m {
 		switch v := v.(type) {
 		case Message:
 			out = append(out, v.Marshal()...)
 		case Tag:
 			out = protowire.AppendTag(out, v.Number, v.Type)
 		case Bool:
 			out = protowire.AppendVarint(out, protowire.EncodeBool(bool(v)))
 		case Varint:
 			out = protowire.AppendVarint(out, uint64(v))
 		case Svarint:
 			out = protowire.AppendVarint(out, protowire.EncodeZigZag(int64(v)))
 		case Uvarint:
 			out = protowire.AppendVarint(out, uint64(v))
 		case Int32:
 			out = protowire.AppendFixed32(out, uint32(v))
 		case Uint32:
 			out = protowire.AppendFixed32(out, uint32(v))
 		case Float32:
 			out = protowire.AppendFixed32(out, math.Float32bits(float32(v)))
 		case Int64:
 			out = protowire.AppendFixed64(out, uint64(v))
 		case Uint64:
 			out = protowire.AppendFixed64(out, uint64(v))
 		case Float64:
 			out = protowire.AppendFixed64(out, math.Float64bits(float64(v)))
 		case String:
 			out = protowire.AppendBytes(out, []byte(v))
 		case Bytes:
 			out = protowire.AppendBytes(out, []byte(v))
 		case LengthPrefix:
 			out = protowire.AppendBytes(out, Message(v).Marshal())
 		case Denormalized:
 			b := Message{v.Value}.Marshal()
 			_, n := protowire.ConsumeVarint(b)
 			out = append(out, b[:n]...)
 			for i := uint(0); i < v.Count; i++ {
 				out[len(out)-1] |= 0x80 // set continuation bit on previous
 				out = append(out, 0)
 			}
 			out = append(out, b[n:]...)
 		case Raw:
 			return append(out, v...)
 		default:
 			panic(fmt.Sprintf("unknown type: %T", v))
 		}
 	}
 	return out
 }

 // Unmarshal parses the input protobuf wire data as a syntax tree.
 // Any parsing error results in the remainder of the input being
 // concatenated to the message as a [Raw] type.
 //
 // Each tag (a tuple of the field number and wire type) encountered is
 // inserted into the syntax tree as a [Tag].
 //
 // The contents of each wire type is mapped to the following Go types:
 //
 //   - [VarintType] ⇒ [Uvarint]
 //   - [Fixed32Type] ⇒ [Uint32]
 //   - [Fixed64Type] ⇒ [Uint64]
 //   - [BytesType] ⇒ [Bytes]
 //   - [StartGroupType] and [StartGroupType] ⇒ [Message]
 //
 // Since the wire format is not self-describing, this function cannot parse
 // sub-messages and will leave them as the [Bytes] type. Further manual parsing
 // can be performed as such:
 //
 //	var m, m1, m2 Message
 //	m.Unmarshal(b)
 //	m1.Unmarshal(m[3].(Bytes))
 //	m[3] = LengthPrefix(m1)
 //	m2.Unmarshal(m[3].(LengthPrefix)[1].(Bytes))
 //	m[3].(LengthPrefix)[1] = LengthPrefix(m2)
 //
 // Unmarshal is useful for debugging the protobuf wire format.
 func (m *Message) Unmarshal(in []byte) {
 	m.unmarshal(in, nil, false)
 }

 // UnmarshalDescriptor parses the input protobuf wire data as a syntax tree
 // using the provided message descriptor for more accurate parsing of fields.
 // It operates like [Message.Unmarshal], but may use a wider range of Go types to
 // represent the wire data.
 //
 // The contents of each wire type is mapped to one of the following Go types:
 //
 //   - [VarintType] ⇒ [Bool], [Varint], [Svarint], [Uvarint]
 //   - [Fixed32Type] ⇒ [Int32], [Uint32], [Float32]
 //   - [Fixed64Type] ⇒ [Uint32], [Uint64], [Float64]
 //   - [BytesType] ⇒ [String], [Bytes], [LengthPrefix]
 //   - [StartGroupType] and [StartGroupType] ⇒ [Message]
 //
 // If the field is unknown, it uses the same mapping as [Message.Unmarshal].
 // Known sub-messages are parsed as a Message and packed repeated fields are
 // parsed as a [LengthPrefix].
 func (m *Message) UnmarshalDescriptor(in []byte, desc protoreflect.MessageDescriptor) {
 	m.unmarshal(in, desc, false)
 }

 // UnmarshalAbductive is like [Message.UnmarshalDescriptor], but infers abductively
 // whether any unknown bytes values is a message based on whether it is
 // a syntactically well-formed message.
 //
 // Note that the protobuf wire format is not fully self-describing,
 // so abductive inference may attempt to expand a bytes value as a message
 // that is not actually a message. It is a best-effort guess.
 func (m *Message) UnmarshalAbductive(in []byte, desc protoreflect.MessageDescriptor) {
 	m.unmarshal(in, desc, true)
 }

 func (m *Message) unmarshal(in []byte, desc protoreflect.MessageDescriptor, inferMessage bool) {
 	p := parser{in: in, out: *m}
 	p.parseMessage(desc, false, inferMessage)
 	*m = p.out
 }

 type parser struct {
 	in  []byte
 	out []Token

 	invalid bool
 }

 func (p *parser) parseMessage(msgDesc protoreflect.MessageDescriptor, group, inferMessage bool) {
 	for len(p.in) > 0 {
 		v, n := protowire.ConsumeVarint(p.in)
 		num, typ := protowire.DecodeTag(v)
 		if n < 0 || num <= 0 || v > math.MaxUint32 {
 			p.out, p.in = append(p.out, Raw(p.in)), nil
 			p.invalid = true
 			return
 		}
 		if typ == EndGroupType && group {
 			return // if inside a group, then stop
 		}
 		p.out, p.in = append(p.out, Tag{num, typ}), p.in[n:]
 		if m := n - protowire.SizeVarint(v); m > 0 {
 			p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
 		}

 		// If descriptor is available, use it for more accurate parsing.
 		var isPacked bool
 		var kind protoreflect.Kind
 		var subDesc protoreflect.MessageDescriptor
 		if msgDesc != nil && !msgDesc.IsPlaceholder() {
 			if fieldDesc := msgDesc.Fields().ByNumber(num); fieldDesc != nil {
 				isPacked = fieldDesc.IsPacked()
 				kind = fieldDesc.Kind()
 				switch kind {
 				case protoreflect.MessageKind, protoreflect.GroupKind:
 					subDesc = fieldDesc.Message()
 					if subDesc == nil || subDesc.IsPlaceholder() {
 						kind = 0
 					}
 				}
 			}
 		}

 		switch typ {
 		case VarintType:
 			p.parseVarint(kind)
 		case Fixed32Type:
 			p.parseFixed32(kind)
 		case Fixed64Type:
 			p.parseFixed64(kind)
 		case BytesType:
 			p.parseBytes(isPacked, kind, subDesc, inferMessage)
 		case StartGroupType:
 			p.parseGroup(num, subDesc, inferMessage)
 		case EndGroupType:
 			// Handled by p.parseGroup.
 		default:
 			p.out, p.in = append(p.out, Raw(p.in)), nil
 			p.invalid = true
 		}
 	}
 }

 func (p *parser) parseVarint(kind protoreflect.Kind) {
 	v, n := protowire.ConsumeVarint(p.in)
 	if n < 0 {
 		p.out, p.in = append(p.out, Raw(p.in)), nil
 		p.invalid = true
 		return
 	}
 	switch kind {
 	case protoreflect.BoolKind:
 		switch v {
 		case 0:
 			p.out, p.in = append(p.out, Bool(false)), p.in[n:]
 		case 1:
 			p.out, p.in = append(p.out, Bool(true)), p.in[n:]
 		default:
 			p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
 		}
 	case protoreflect.Int32Kind, protoreflect.Int64Kind:
 		p.out, p.in = append(p.out, Varint(v)), p.in[n:]
 	case protoreflect.Sint32Kind, protoreflect.Sint64Kind:
 		p.out, p.in = append(p.out, Svarint(protowire.DecodeZigZag(v))), p.in[n:]
 	default:
 		p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
 	}
 	if m := n - protowire.SizeVarint(v); m > 0 {
 		p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
 	}
 }

 func (p *parser) parseFixed32(kind protoreflect.Kind) {
 	v, n := protowire.ConsumeFixed32(p.in)
 	if n < 0 {
 		p.out, p.in = append(p.out, Raw(p.in)), nil
 		p.invalid = true
 		return
 	}
 	switch kind {
 	case protoreflect.FloatKind:
 		p.out, p.in = append(p.out, Float32(math.Float32frombits(v))), p.in[n:]
 	case protoreflect.Sfixed32Kind:
 		p.out, p.in = append(p.out, Int32(v)), p.in[n:]
 	default:
 		p.out, p.in = append(p.out, Uint32(v)), p.in[n:]
 	}
 }

 func (p *parser) parseFixed64(kind protoreflect.Kind) {
 	v, n := protowire.ConsumeFixed64(p.in)
 	if n < 0 {
 		p.out, p.in = append(p.out, Raw(p.in)), nil
 		p.invalid = true
 		return
 	}
 	switch kind {
 	case protoreflect.DoubleKind:
 		p.out, p.in = append(p.out, Float64(math.Float64frombits(v))), p.in[n:]
 	case protoreflect.Sfixed64Kind:
 		p.out, p.in = append(p.out, Int64(v)), p.in[n:]
 	default:
 		p.out, p.in = append(p.out, Uint64(v)), p.in[n:]
 	}
 }

 func (p *parser) parseBytes(isPacked bool, kind protoreflect.Kind, desc protoreflect.MessageDescriptor, inferMessage bool) {
 	v, n := protowire.ConsumeVarint(p.in)
 	if n < 0 {
 		p.out, p.in = append(p.out, Raw(p.in)), nil
 		p.invalid = true
 		return
 	}
 	p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
 	if m := n - protowire.SizeVarint(v); m > 0 {
 		p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
 	}
 	if v > uint64(len(p.in)) {
 		p.out, p.in = append(p.out, Raw(p.in)), nil
 		p.invalid = true
 		return
 	}
 	p.out = p.out[:len(p.out)-1] // subsequent tokens contain prefix-length

 	if isPacked {
 		p.parsePacked(int(v), kind)
 	} else {
 		switch kind {
 		case protoreflect.MessageKind:
 			p2 := parser{in: p.in[:v]}
 			p2.parseMessage(desc, false, inferMessage)
 			p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[v:]
 		case protoreflect.StringKind:
 			p.out, p.in = append(p.out, String(p.in[:v])), p.in[v:]
 		case protoreflect.BytesKind:
 			p.out, p.in = append(p.out, Bytes(p.in[:v])), p.in[v:]
 		default:
 			if inferMessage {
 				// Check whether this is a syntactically valid message.
 				p2 := parser{in: p.in[:v]}
 				p2.parseMessage(nil, false, inferMessage)
 				if !p2.invalid {
 					p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[v:]
 					break
 				}
 			}
 			p.out, p.in = append(p.out, Bytes(p.in[:v])), p.in[v:]
 		}
 	}
 	if m := n - protowire.SizeVarint(v); m > 0 {
 		p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
 	}
 }

 func (p *parser) parsePacked(n int, kind protoreflect.Kind) {
 	p2 := parser{in: p.in[:n]}
 	for len(p2.in) > 0 {
 		switch kind {
 		case protoreflect.BoolKind, protoreflect.EnumKind,
 			protoreflect.Int32Kind, protoreflect.Sint32Kind, protoreflect.Uint32Kind,
 			protoreflect.Int64Kind, protoreflect.Sint64Kind, protoreflect.Uint64Kind:
 			p2.parseVarint(kind)
 		case protoreflect.Fixed32Kind, protoreflect.Sfixed32Kind, protoreflect.FloatKind:
 			p2.parseFixed32(kind)
 		case protoreflect.Fixed64Kind, protoreflect.Sfixed64Kind, protoreflect.DoubleKind:
 			p2.parseFixed64(kind)
 		default:
 			panic(fmt.Sprintf("invalid packed kind: %v", kind))
 		}
 	}
 	p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[n:]
 }

 func (p *parser) parseGroup(startNum protowire.Number, desc protoreflect.MessageDescriptor, inferMessage bool) {
 	p2 := parser{in: p.in}
 	p2.parseMessage(desc, true, inferMessage)
 	if len(p2.out) > 0 {
 		p.out = append(p.out, Message(p2.out))
 	}
 	p.in = p2.in

 	// Append the trailing end group.
 	v, n := protowire.ConsumeVarint(p.in)
 	if endNum, typ := protowire.DecodeTag(v); typ == EndGroupType {
 		if startNum != endNum {
 			p.invalid = true
 		}
 		p.out, p.in = append(p.out, Tag{endNum, typ}), p.in[n:]
 		if m := n - protowire.SizeVarint(v); m > 0 {
 			p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
 		}
 	}
 }

 // Format implements a custom formatter to visualize the syntax tree.
 // Using "%#v" formats the Message in Go source code.
 func (m Message) Format(s fmt.State, r rune) {
 	switch r {
 	case 'x':
 		io.WriteString(s, fmt.Sprintf("%x", m.Marshal()))
 	case 'X':
 		io.WriteString(s, fmt.Sprintf("%X", m.Marshal()))
 	case 'v':
 		switch {
 		case s.Flag('#'):
 			io.WriteString(s, m.format(true, true))
 		case s.Flag('+'):
 			io.WriteString(s, m.format(false, true))
 		default:
 			io.WriteString(s, m.format(false, false))
 		}
 	default:
 		panic("invalid verb: " + string(r))
 	}
 }

 // format formats the message.
 // If source is enabled, this emits valid Go source.
 // If multi is enabled, the output may span multiple lines.
 func (m Message) format(source, multi bool) string {
 	var ss []string
 	var prefix, nextPrefix string
 	for _, v := range m {
 		// Ensure certain tokens have preceding or succeeding newlines.
 		prefix, nextPrefix = nextPrefix, " "
 		if multi {
 			switch v := v.(type) {
 			case Tag: // only has preceding newline
 				prefix = "\n"
 			case Denormalized: // only has preceding newline
 				if _, ok := v.Value.(Tag); ok {
 					prefix = "\n"
 				}
 			case Message, Raw: // has preceding and succeeding newlines
 				prefix, nextPrefix = "\n", "\n"
 			}
 		}

 		s := formatToken(v, source, multi)
 		ss = append(ss, prefix+s+",")
 	}

 	var s string
 	if len(ss) > 0 {
 		s = strings.TrimSpace(strings.Join(ss, ""))
 		if multi {
 			s = "\n\t" + strings.Join(strings.Split(s, "\n"), "\n\t") + "\n"
 		} else {
 			s = strings.TrimSuffix(s, ",")
 		}
 	}
 	s = fmt.Sprintf("%T{%s}", m, s)
 	if !source {
 		s = trimPackage(s)
 	}
 	return s
 }

 // formatToken formats a single token.
 func formatToken(t Token, source, multi bool) (s string) {
 	switch v := t.(type) {
 	case Message:
 		s = v.format(source, multi)
 	case LengthPrefix:
 		s = formatPacked(v, source, multi)
 		if s == "" {
 			ms := Message(v).format(source, multi)
 			s = fmt.Sprintf("%T(%s)", v, ms)
 		}
 	case Tag:
 		s = fmt.Sprintf("%T{%d, %s}", v, v.Number, formatType(v.Type, source))
 	case Bool, Varint, Svarint, Uvarint, Int32, Uint32, Float32, Int64, Uint64, Float64:
 		if source {
 			// Print floats in a way that preserves exact precision.
 			if f, _ := v.(Float32); math.IsNaN(float64(f)) || math.IsInf(float64(f), 0) {
 				switch {
 				case f > 0:
 					s = fmt.Sprintf("%T(math.Inf(+1))", v)
 				case f < 0:
 					s = fmt.Sprintf("%T(math.Inf(-1))", v)
 				case math.Float32bits(float32(math.NaN())) == math.Float32bits(float32(f)):
 					s = fmt.Sprintf("%T(math.NaN())", v)
 				default:
 					s = fmt.Sprintf("%T(math.Float32frombits(0x%08x))", v, math.Float32bits(float32(f)))
 				}
 				break
 			}
 			if f, _ := v.(Float64); math.IsNaN(float64(f)) || math.IsInf(float64(f), 0) {
 				switch {
 				case f > 0:
 					s = fmt.Sprintf("%T(math.Inf(+1))", v)
 				case f < 0:
 					s = fmt.Sprintf("%T(math.Inf(-1))", v)
 				case math.Float64bits(float64(math.NaN())) == math.Float64bits(float64(f)):
 					s = fmt.Sprintf("%T(math.NaN())", v)
 				default:
 					s = fmt.Sprintf("%T(math.Float64frombits(0x%016x))", v, math.Float64bits(float64(f)))
 				}
 				break
 			}
 		}
 		s = fmt.Sprintf("%T(%v)", v, v)
 	case String, Bytes, Raw:
 		s = fmt.Sprintf("%s", v)
 		s = fmt.Sprintf("%T(%s)", v, formatString(s))
 	case Denormalized:
 		s = fmt.Sprintf("%T{+%d, %v}", v, v.Count, formatToken(v.Value, source, multi))
 	default:
 		panic(fmt.Sprintf("unknown type: %T", v))
 	}
 	if !source {
 		s = trimPackage(s)
 	}
 	return s
 }

 // formatPacked returns a non-empty string if LengthPrefix looks like a packed
 // repeated field of primitives.
 func formatPacked(v LengthPrefix, source, multi bool) string {
 	var ss []string
 	for _, v := range v {
 		switch v.(type) {
 		case Bool, Varint, Svarint, Uvarint, Int32, Uint32, Float32, Int64, Uint64, Float64, Denormalized, Raw:
 			if v, ok := v.(Denormalized); ok {
 				switch v.Value.(type) {
 				case Bool, Varint, Svarint, Uvarint:
 				default:
 					return ""
 				}
 			}
 			ss = append(ss, formatToken(v, source, multi))
 		default:
 			return ""
 		}
 	}
 	s := fmt.Sprintf("%T{%s}", v, strings.Join(ss, ", "))
 	if !source {
 		s = trimPackage(s)
 	}
 	return s
 }

 // formatType returns the name for Type.
 func formatType(t Type, source bool) (s string) {
 	switch t {
 	case VarintType:
 		s = pkg + ".VarintType"
 	case Fixed32Type:
 		s = pkg + ".Fixed32Type"
 	case Fixed64Type:
 		s = pkg + ".Fixed64Type"
 	case BytesType:
 		s = pkg + ".BytesType"
 	case StartGroupType:
 		s = pkg + ".StartGroupType"
 	case EndGroupType:
 		s = pkg + ".EndGroupType"
 	default:
 		s = fmt.Sprintf("Type(%d)", t)
 	}
 	if !source {
 		s = strings.TrimSuffix(trimPackage(s), "Type")
 	}
 	return s
 }

 // formatString returns a quoted string for s.
 func formatString(s string) string {
 	// Use quoted string if it the same length as a raw string literal.
 	// Otherwise, attempt to use the raw string form.
 	qs := strconv.Quote(s)
 	if len(qs) == 1+len(s)+1 {
 		return qs
 	}

 	// Disallow newlines to ensure output is a single line.
 	// Disallow non-printable runes for readability purposes.
 	rawInvalid := func(r rune) bool {
 		return r == '`' || r == '\n' || r == utf8.RuneError || !unicode.IsPrint(r)
 	}
 	if strings.IndexFunc(s, rawInvalid) < 0 {
 		return "`" + s + "`"
 	}
 	return qs
 }

 var pkg = path.Base(reflect.TypeOf(Tag{}).PkgPath())

 func trimPackage(s string) string {
 	return strings.TrimPrefix(strings.TrimPrefix(s, pkg), ".")
 }
	// Copyright 2018 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 protopack enables manual encoding and decoding of protobuf wire data.
	//
	// This package is intended for use in debugging and/or creation of test data.
	// Proper usage of this package requires knowledge of the wire format.
	//
	// See https://protobuf.dev/programming-guides/encoding.
	package protopack

	import (
	"fmt"
	"io"
	"math"
	"path"
	"reflect"
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"

	"google.golang.org/protobuf/encoding/protowire"
	"google.golang.org/protobuf/reflect/protoreflect"
	)

	// Number is the field number; aliased from the [protowire] package for convenience.
	type Number = protowire.Number

	// Number type constants; copied from the [protowire] package for convenience.
	const (
	MinValidNumber Number = protowire.MinValidNumber
	FirstReservedNumber Number = protowire.FirstReservedNumber
	LastReservedNumber Number = protowire.LastReservedNumber
	MaxValidNumber Number = protowire.MaxValidNumber
	)

	// Type is the wire type; aliased from the [protowire] package for convenience.
	type Type = protowire.Type

	// Wire type constants; copied from the [protowire] package for convenience.
	const (
	VarintType Type = protowire.VarintType
	Fixed32Type Type = protowire.Fixed32Type
	Fixed64Type Type = protowire.Fixed64Type
	BytesType Type = protowire.BytesType
	StartGroupType Type = protowire.StartGroupType
	EndGroupType Type = protowire.EndGroupType
	)

	type (
	// Token is any other type (e.g., [Message], [Tag], [Varint], [Float32], etc).
	Token token
	// Message is an ordered sequence of [Token] values, where certain tokens may
	// contain other tokens. It is functionally a concrete syntax tree that
	// losslessly represents any arbitrary wire data (including invalid input).
	Message []Token

	// Tag is a tuple of the field number and the wire type.
	Tag struct {
	Number Number
	Type Type
	}
	// Bool is a boolean.
	Bool bool
	// Varint is a signed varint using 64-bit two's complement encoding.
	Varint int64
	// Svarint is a signed varint using zig-zag encoding.
	Svarint int64
	// Uvarint is a unsigned varint.
	Uvarint uint64

	// Int32 is a signed 32-bit fixed-width integer.
	Int32 int32
	// Uint32 is an unsigned 32-bit fixed-width integer.
	Uint32 uint32
	// Float32 is a 32-bit fixed-width floating point number.
	Float32 float32

	// Int64 is a signed 64-bit fixed-width integer.
	Int64 int64
	// Uint64 is an unsigned 64-bit fixed-width integer.
	Uint64 uint64
	// Float64 is a 64-bit fixed-width floating point number.
	Float64 float64

	// String is a length-prefixed string.
	String string
	// Bytes is a length-prefixed bytes.
	Bytes []byte
	// LengthPrefix is a length-prefixed message.
	LengthPrefix Message

	// Denormalized is a denormalized varint value, where a varint is encoded
	// using more bytes than is strictly necessary. The number of extra bytes
	// alone is sufficient to losslessly represent the denormalized varint.
	//
	// The value may be one of [Tag], [Bool], [Varint], [Svarint], or [Uvarint],
	// where the varint representation of each token is denormalized.
	//
	// Alternatively, the value may be one of [String], [Bytes], or [LengthPrefix],
	// where the varint representation of the length-prefix is denormalized.
	Denormalized struct {
	Count uint // number of extra bytes
	Value Token
	}

	// Raw are bytes directly appended to output.
	Raw []byte
	)

	type token interface {
	isToken()
	}

	func (Message) isToken() {}
	func (Tag) isToken() {}
	func (Bool) isToken() {}
	func (Varint) isToken() {}
	func (Svarint) isToken() {}
	func (Uvarint) isToken() {}
	func (Int32) isToken() {}
	func (Uint32) isToken() {}
	func (Float32) isToken() {}
	func (Int64) isToken() {}
	func (Uint64) isToken() {}
	func (Float64) isToken() {}
	func (String) isToken() {}
	func (Bytes) isToken() {}
	func (LengthPrefix) isToken() {}
	func (Denormalized) isToken() {}
	func (Raw) isToken() {}

	// Size reports the size in bytes of the marshaled message.
	func (m Message) Size() int {
	var n int
	for _, v := range m {
	switch v := v.(type) {
	case Message:
	n += v.Size()
	case Tag:
	n += protowire.SizeTag(v.Number)
	case Bool:
	n += protowire.SizeVarint(protowire.EncodeBool(false))
	case Varint:
	n += protowire.SizeVarint(uint64(v))
	case Svarint:
	n += protowire.SizeVarint(protowire.EncodeZigZag(int64(v)))
	case Uvarint:
	n += protowire.SizeVarint(uint64(v))
	case Int32, Uint32, Float32:
	n += protowire.SizeFixed32()
	case Int64, Uint64, Float64:
	n += protowire.SizeFixed64()
	case String:
	n += protowire.SizeBytes(len(v))
	case Bytes:
	n += protowire.SizeBytes(len(v))
	case LengthPrefix:
	n += protowire.SizeBytes(Message(v).Size())
	case Denormalized:
	n += int(v.Count) + Message{v.Value}.Size()
	case Raw:
	n += len(v)
	default:
	panic(fmt.Sprintf("unknown type: %T", v))
	}
	}
	return n
	}

	// Marshal encodes a syntax tree into the protobuf wire format.
	//
	// Example message definition:
	//
	// message MyMessage {
	// string field1 = 1;
	// int64 field2 = 2;
	// repeated float32 field3 = 3;
	// }
	//
	// Example encoded message:
	//
	// b := Message{
	// Tag{1, BytesType}, String("Hello, world!"),
	// Tag{2, VarintType}, Varint(-10),
	// Tag{3, BytesType}, LengthPrefix{
	// Float32(1.1), Float32(2.2), Float32(3.3),
	// },
	// }.Marshal()
	//
	// Resulting wire data:
	//
	// 0x0000 0a 0d 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 10 \|..Hello, world!.\|
	// 0x0010 f6 ff ff ff ff ff ff ff ff 01 1a 0c cd cc 8c 3f \|...............?\|
	// 0x0020 cd cc 0c 40 33 33 53 40 \|...@33S@\|
	func (m Message) Marshal() []byte {
	var out []byte
	for _, v := range m {
	switch v := v.(type) {
	case Message:
	out = append(out, v.Marshal()...)
	case Tag:
	out = protowire.AppendTag(out, v.Number, v.Type)
	case Bool:
	out = protowire.AppendVarint(out, protowire.EncodeBool(bool(v)))
	case Varint:
	out = protowire.AppendVarint(out, uint64(v))
	case Svarint:
	out = protowire.AppendVarint(out, protowire.EncodeZigZag(int64(v)))
	case Uvarint:
	out = protowire.AppendVarint(out, uint64(v))
	case Int32:
	out = protowire.AppendFixed32(out, uint32(v))
	case Uint32:
	out = protowire.AppendFixed32(out, uint32(v))
	case Float32:
	out = protowire.AppendFixed32(out, math.Float32bits(float32(v)))
	case Int64:
	out = protowire.AppendFixed64(out, uint64(v))
	case Uint64:
	out = protowire.AppendFixed64(out, uint64(v))
	case Float64:
	out = protowire.AppendFixed64(out, math.Float64bits(float64(v)))
	case String:
	out = protowire.AppendBytes(out, []byte(v))
	case Bytes:
	out = protowire.AppendBytes(out, []byte(v))
	case LengthPrefix:
	out = protowire.AppendBytes(out, Message(v).Marshal())
	case Denormalized:
	b := Message{v.Value}.Marshal()
	_, n := protowire.ConsumeVarint(b)
	out = append(out, b[:n]...)
	for i := uint(0); i < v.Count; i++ {
	out[len(out)-1] \|= 0x80 // set continuation bit on previous
	out = append(out, 0)
	}
	out = append(out, b[n:]...)
	case Raw:
	return append(out, v...)
	default:
	panic(fmt.Sprintf("unknown type: %T", v))
	}
	}
	return out
	}

	// Unmarshal parses the input protobuf wire data as a syntax tree.
	// Any parsing error results in the remainder of the input being
	// concatenated to the message as a [Raw] type.
	//
	// Each tag (a tuple of the field number and wire type) encountered is
	// inserted into the syntax tree as a [Tag].
	//
	// The contents of each wire type is mapped to the following Go types:
	//
	// - [VarintType] ⇒ [Uvarint]
	// - [Fixed32Type] ⇒ [Uint32]
	// - [Fixed64Type] ⇒ [Uint64]
	// - [BytesType] ⇒ [Bytes]
	// - [StartGroupType] and [StartGroupType] ⇒ [Message]
	//
	// Since the wire format is not self-describing, this function cannot parse
	// sub-messages and will leave them as the [Bytes] type. Further manual parsing
	// can be performed as such:
	//
	// var m, m1, m2 Message
	// m.Unmarshal(b)
	// m1.Unmarshal(m[3].(Bytes))
	// m[3] = LengthPrefix(m1)
	// m2.Unmarshal(m[3].(LengthPrefix)[1].(Bytes))
	// m[3].(LengthPrefix)[1] = LengthPrefix(m2)
	//
	// Unmarshal is useful for debugging the protobuf wire format.
	func (m *Message) Unmarshal(in []byte) {
	m.unmarshal(in, nil, false)
	}

	// UnmarshalDescriptor parses the input protobuf wire data as a syntax tree
	// using the provided message descriptor for more accurate parsing of fields.
	// It operates like [Message.Unmarshal], but may use a wider range of Go types to
	// represent the wire data.
	//
	// The contents of each wire type is mapped to one of the following Go types:
	//
	// - [VarintType] ⇒ [Bool], [Varint], [Svarint], [Uvarint]
	// - [Fixed32Type] ⇒ [Int32], [Uint32], [Float32]
	// - [Fixed64Type] ⇒ [Uint32], [Uint64], [Float64]
	// - [BytesType] ⇒ [String], [Bytes], [LengthPrefix]
	// - [StartGroupType] and [StartGroupType] ⇒ [Message]
	//
	// If the field is unknown, it uses the same mapping as [Message.Unmarshal].
	// Known sub-messages are parsed as a Message and packed repeated fields are
	// parsed as a [LengthPrefix].
	func (m *Message) UnmarshalDescriptor(in []byte, desc protoreflect.MessageDescriptor) {
	m.unmarshal(in, desc, false)
	}

	// UnmarshalAbductive is like [Message.UnmarshalDescriptor], but infers abductively
	// whether any unknown bytes values is a message based on whether it is
	// a syntactically well-formed message.
	//
	// Note that the protobuf wire format is not fully self-describing,
	// so abductive inference may attempt to expand a bytes value as a message
	// that is not actually a message. It is a best-effort guess.
	func (m *Message) UnmarshalAbductive(in []byte, desc protoreflect.MessageDescriptor) {
	m.unmarshal(in, desc, true)
	}

	func (m *Message) unmarshal(in []byte, desc protoreflect.MessageDescriptor, inferMessage bool) {
	p := parser{in: in, out: *m}
	p.parseMessage(desc, false, inferMessage)
	*m = p.out
	}

	type parser struct {
	in []byte
	out []Token

	invalid bool
	}

	func (p *parser) parseMessage(msgDesc protoreflect.MessageDescriptor, group, inferMessage bool) {
	for len(p.in) > 0 {
	v, n := protowire.ConsumeVarint(p.in)
	num, typ := protowire.DecodeTag(v)
	if n < 0 \|\| num <= 0 \|\| v > math.MaxUint32 {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	if typ == EndGroupType && group {
	return // if inside a group, then stop
	}
	p.out, p.in = append(p.out, Tag{num, typ}), p.in[n:]
	if m := n - protowire.SizeVarint(v); m > 0 {
	p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
	}

	// If descriptor is available, use it for more accurate parsing.
	var isPacked bool
	var kind protoreflect.Kind
	var subDesc protoreflect.MessageDescriptor
	if msgDesc != nil && !msgDesc.IsPlaceholder() {
	if fieldDesc := msgDesc.Fields().ByNumber(num); fieldDesc != nil {
	isPacked = fieldDesc.IsPacked()
	kind = fieldDesc.Kind()
	switch kind {
	case protoreflect.MessageKind, protoreflect.GroupKind:
	subDesc = fieldDesc.Message()
	if subDesc == nil \|\| subDesc.IsPlaceholder() {
	kind = 0
	}
	}
	}
	}

	switch typ {
	case VarintType:
	p.parseVarint(kind)
	case Fixed32Type:
	p.parseFixed32(kind)
	case Fixed64Type:
	p.parseFixed64(kind)
	case BytesType:
	p.parseBytes(isPacked, kind, subDesc, inferMessage)
	case StartGroupType:
	p.parseGroup(num, subDesc, inferMessage)
	case EndGroupType:
	// Handled by p.parseGroup.
	default:
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	}
	}
	}

	func (p *parser) parseVarint(kind protoreflect.Kind) {
	v, n := protowire.ConsumeVarint(p.in)
	if n < 0 {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	switch kind {
	case protoreflect.BoolKind:
	switch v {
	case 0:
	p.out, p.in = append(p.out, Bool(false)), p.in[n:]
	case 1:
	p.out, p.in = append(p.out, Bool(true)), p.in[n:]
	default:
	p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
	}
	case protoreflect.Int32Kind, protoreflect.Int64Kind:
	p.out, p.in = append(p.out, Varint(v)), p.in[n:]
	case protoreflect.Sint32Kind, protoreflect.Sint64Kind:
	p.out, p.in = append(p.out, Svarint(protowire.DecodeZigZag(v))), p.in[n:]
	default:
	p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
	}
	if m := n - protowire.SizeVarint(v); m > 0 {
	p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
	}
	}

	func (p *parser) parseFixed32(kind protoreflect.Kind) {
	v, n := protowire.ConsumeFixed32(p.in)
	if n < 0 {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	switch kind {
	case protoreflect.FloatKind:
	p.out, p.in = append(p.out, Float32(math.Float32frombits(v))), p.in[n:]
	case protoreflect.Sfixed32Kind:
	p.out, p.in = append(p.out, Int32(v)), p.in[n:]
	default:
	p.out, p.in = append(p.out, Uint32(v)), p.in[n:]
	}
	}

	func (p *parser) parseFixed64(kind protoreflect.Kind) {
	v, n := protowire.ConsumeFixed64(p.in)
	if n < 0 {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	switch kind {
	case protoreflect.DoubleKind:
	p.out, p.in = append(p.out, Float64(math.Float64frombits(v))), p.in[n:]
	case protoreflect.Sfixed64Kind:
	p.out, p.in = append(p.out, Int64(v)), p.in[n:]
	default:
	p.out, p.in = append(p.out, Uint64(v)), p.in[n:]
	}
	}

	func (p *parser) parseBytes(isPacked bool, kind protoreflect.Kind, desc protoreflect.MessageDescriptor, inferMessage bool) {
	v, n := protowire.ConsumeVarint(p.in)
	if n < 0 {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	p.out, p.in = append(p.out, Uvarint(v)), p.in[n:]
	if m := n - protowire.SizeVarint(v); m > 0 {
	p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
	}
	if v > uint64(len(p.in)) {
	p.out, p.in = append(p.out, Raw(p.in)), nil
	p.invalid = true
	return
	}
	p.out = p.out[:len(p.out)-1] // subsequent tokens contain prefix-length

	if isPacked {
	p.parsePacked(int(v), kind)
	} else {
	switch kind {
	case protoreflect.MessageKind:
	p2 := parser{in: p.in[:v]}
	p2.parseMessage(desc, false, inferMessage)
	p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[v:]
	case protoreflect.StringKind:
	p.out, p.in = append(p.out, String(p.in[:v])), p.in[v:]
	case protoreflect.BytesKind:
	p.out, p.in = append(p.out, Bytes(p.in[:v])), p.in[v:]
	default:
	if inferMessage {
	// Check whether this is a syntactically valid message.
	p2 := parser{in: p.in[:v]}
	p2.parseMessage(nil, false, inferMessage)
	if !p2.invalid {
	p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[v:]
	break
	}
	}
	p.out, p.in = append(p.out, Bytes(p.in[:v])), p.in[v:]
	}
	}
	if m := n - protowire.SizeVarint(v); m > 0 {
	p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
	}
	}

	func (p *parser) parsePacked(n int, kind protoreflect.Kind) {
	p2 := parser{in: p.in[:n]}
	for len(p2.in) > 0 {
	switch kind {
	case protoreflect.BoolKind, protoreflect.EnumKind,
	protoreflect.Int32Kind, protoreflect.Sint32Kind, protoreflect.Uint32Kind,
	protoreflect.Int64Kind, protoreflect.Sint64Kind, protoreflect.Uint64Kind:
	p2.parseVarint(kind)
	case protoreflect.Fixed32Kind, protoreflect.Sfixed32Kind, protoreflect.FloatKind:
	p2.parseFixed32(kind)
	case protoreflect.Fixed64Kind, protoreflect.Sfixed64Kind, protoreflect.DoubleKind:
	p2.parseFixed64(kind)
	default:
	panic(fmt.Sprintf("invalid packed kind: %v", kind))
	}
	}
	p.out, p.in = append(p.out, LengthPrefix(p2.out)), p.in[n:]
	}

	func (p *parser) parseGroup(startNum protowire.Number, desc protoreflect.MessageDescriptor, inferMessage bool) {
	p2 := parser{in: p.in}
	p2.parseMessage(desc, true, inferMessage)
	if len(p2.out) > 0 {
	p.out = append(p.out, Message(p2.out))
	}
	p.in = p2.in

	// Append the trailing end group.
	v, n := protowire.ConsumeVarint(p.in)
	if endNum, typ := protowire.DecodeTag(v); typ == EndGroupType {
	if startNum != endNum {
	p.invalid = true
	}
	p.out, p.in = append(p.out, Tag{endNum, typ}), p.in[n:]
	if m := n - protowire.SizeVarint(v); m > 0 {
	p.out[len(p.out)-1] = Denormalized{uint(m), p.out[len(p.out)-1]}
	}
	}
	}

	// Format implements a custom formatter to visualize the syntax tree.
	// Using "%#v" formats the Message in Go source code.
	func (m Message) Format(s fmt.State, r rune) {
	switch r {
	case 'x':
	io.WriteString(s, fmt.Sprintf("%x", m.Marshal()))
	case 'X':
	io.WriteString(s, fmt.Sprintf("%X", m.Marshal()))
	case 'v':
	switch {
	case s.Flag('#'):
	io.WriteString(s, m.format(true, true))
	case s.Flag('+'):
	io.WriteString(s, m.format(false, true))
	default:
	io.WriteString(s, m.format(false, false))
	}
	default:
	panic("invalid verb: " + string(r))
	}
	}

	// format formats the message.
	// If source is enabled, this emits valid Go source.
	// If multi is enabled, the output may span multiple lines.
	func (m Message) format(source, multi bool) string {
	var ss []string
	var prefix, nextPrefix string
	for _, v := range m {
	// Ensure certain tokens have preceding or succeeding newlines.
	prefix, nextPrefix = nextPrefix, " "
	if multi {
	switch v := v.(type) {
	case Tag: // only has preceding newline
	prefix = "\n"
	case Denormalized: // only has preceding newline
	if _, ok := v.Value.(Tag); ok {
	prefix = "\n"
	}
	case Message, Raw: // has preceding and succeeding newlines
	prefix, nextPrefix = "\n", "\n"
	}
	}

	s := formatToken(v, source, multi)
	ss = append(ss, prefix+s+",")
	}

	var s string
	if len(ss) > 0 {
	s = strings.TrimSpace(strings.Join(ss, ""))
	if multi {
	s = "\n\t" + strings.Join(strings.Split(s, "\n"), "\n\t") + "\n"
	} else {
	s = strings.TrimSuffix(s, ",")
	}
	}
	s = fmt.Sprintf("%T{%s}", m, s)
	if !source {
	s = trimPackage(s)
	}
	return s
	}

	// formatToken formats a single token.
	func formatToken(t Token, source, multi bool) (s string) {
	switch v := t.(type) {
	case Message:
	s = v.format(source, multi)
	case LengthPrefix:
	s = formatPacked(v, source, multi)
	if s == "" {
	ms := Message(v).format(source, multi)
	s = fmt.Sprintf("%T(%s)", v, ms)
	}
	case Tag:
	s = fmt.Sprintf("%T{%d, %s}", v, v.Number, formatType(v.Type, source))
	case Bool, Varint, Svarint, Uvarint, Int32, Uint32, Float32, Int64, Uint64, Float64:
	if source {
	// Print floats in a way that preserves exact precision.
	if f, _ := v.(Float32); math.IsNaN(float64(f)) \|\| math.IsInf(float64(f), 0) {
	switch {
	case f > 0:
	s = fmt.Sprintf("%T(math.Inf(+1))", v)
	case f < 0:
	s = fmt.Sprintf("%T(math.Inf(-1))", v)
	case math.Float32bits(float32(math.NaN())) == math.Float32bits(float32(f)):
	s = fmt.Sprintf("%T(math.NaN())", v)
	default:
	s = fmt.Sprintf("%T(math.Float32frombits(0x%08x))", v, math.Float32bits(float32(f)))
	}
	break
	}
	if f, _ := v.(Float64); math.IsNaN(float64(f)) \|\| math.IsInf(float64(f), 0) {
	switch {
	case f > 0:
	s = fmt.Sprintf("%T(math.Inf(+1))", v)
	case f < 0:
	s = fmt.Sprintf("%T(math.Inf(-1))", v)
	case math.Float64bits(float64(math.NaN())) == math.Float64bits(float64(f)):
	s = fmt.Sprintf("%T(math.NaN())", v)
	default:
	s = fmt.Sprintf("%T(math.Float64frombits(0x%016x))", v, math.Float64bits(float64(f)))
	}
	break
	}
	}
	s = fmt.Sprintf("%T(%v)", v, v)
	case String, Bytes, Raw:
	s = fmt.Sprintf("%s", v)
	s = fmt.Sprintf("%T(%s)", v, formatString(s))
	case Denormalized:
	s = fmt.Sprintf("%T{+%d, %v}", v, v.Count, formatToken(v.Value, source, multi))
	default:
	panic(fmt.Sprintf("unknown type: %T", v))
	}
	if !source {
	s = trimPackage(s)
	}
	return s
	}

	// formatPacked returns a non-empty string if LengthPrefix looks like a packed
	// repeated field of primitives.
	func formatPacked(v LengthPrefix, source, multi bool) string {
	var ss []string
	for _, v := range v {
	switch v.(type) {
	case Bool, Varint, Svarint, Uvarint, Int32, Uint32, Float32, Int64, Uint64, Float64, Denormalized, Raw:
	if v, ok := v.(Denormalized); ok {
	switch v.Value.(type) {
	case Bool, Varint, Svarint, Uvarint:
	default:
	return ""
	}
	}
	ss = append(ss, formatToken(v, source, multi))
	default:
	return ""
	}
	}
	s := fmt.Sprintf("%T{%s}", v, strings.Join(ss, ", "))
	if !source {
	s = trimPackage(s)
	}
	return s
	}

	// formatType returns the name for Type.
	func formatType(t Type, source bool) (s string) {
	switch t {
	case VarintType:
	s = pkg + ".VarintType"
	case Fixed32Type:
	s = pkg + ".Fixed32Type"
	case Fixed64Type:
	s = pkg + ".Fixed64Type"
	case BytesType:
	s = pkg + ".BytesType"
	case StartGroupType:
	s = pkg + ".StartGroupType"
	case EndGroupType:
	s = pkg + ".EndGroupType"
	default:
	s = fmt.Sprintf("Type(%d)", t)
	}
	if !source {
	s = strings.TrimSuffix(trimPackage(s), "Type")
	}
	return s
	}

	// formatString returns a quoted string for s.
	func formatString(s string) string {
	// Use quoted string if it the same length as a raw string literal.
	// Otherwise, attempt to use the raw string form.
	qs := strconv.Quote(s)
	if len(qs) == 1+len(s)+1 {
	return qs
	}

	// Disallow newlines to ensure output is a single line.
	// Disallow non-printable runes for readability purposes.
	rawInvalid := func(r rune) bool {
	return r == '`' \|\| r == '\n' \|\| r == utf8.RuneError \|\| !unicode.IsPrint(r)
	}
	if strings.IndexFunc(s, rawInvalid) < 0 {
	return "`" + s + "`"
	}
	return qs
	}

	var pkg = path.Base(reflect.TypeOf(Tag{}).PkgPath())

	func trimPackage(s string) string {
	return strings.TrimPrefix(strings.TrimPrefix(s, pkg), ".")
	}