Source: text_encode.go in package github.com/golang/protobuf/proto


package proto

import (
	"bytes"
	"encoding"
	"fmt"
	"io"
	"math"
	"sort"
	"strings"

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

const wrapTextMarshalV2 = false

TextMarshaler is a configurable text format marshaler.

type TextMarshaler struct {
	Compact   bool // use compact text format (one line)
	ExpandAny bool // expand google.protobuf.Any messages of known types
}

Marshal writes the proto text format of m to w.

func (tm *TextMarshaler) Marshal(w io.Writer, m Message) error {
	b, err := tm.marshal(m)
	if len(b) > 0 {
		if _, err := w.Write(b); err != nil {
			return err
		}
	}
	return err
}

Text returns a proto text formatted string of m.

func (tm *TextMarshaler) Text(m Message) string {
	b, _ := tm.marshal(m)
	return string(b)
}

func (tm *TextMarshaler) marshal(m Message) ([]byte, error) {
	mr := MessageReflect(m)
	if mr == nil || !mr.IsValid() {
		return []byte("<nil>"), nil
	}

	if wrapTextMarshalV2 {
		if m, ok := m.(encoding.TextMarshaler); ok {
			return m.MarshalText()
		}

		opts := prototext.MarshalOptions{
			AllowPartial: true,
			EmitUnknown:  true,
		}
		if !tm.Compact {
			opts.Indent = "  "
		}
		if !tm.ExpandAny {
			opts.Resolver = (*protoregistry.Types)(nil)
		}
		return opts.Marshal(mr.Interface())
	} else {
		w := &textWriter{
			compact:   tm.Compact,
			expandAny: tm.ExpandAny,
			complete:  true,
		}

		if m, ok := m.(encoding.TextMarshaler); ok {
			b, err := m.MarshalText()
			if err != nil {
				return nil, err
			}
			w.Write(b)
			return w.buf, nil
		}

		err := w.writeMessage(mr)
		return w.buf, err
	}
}

var (
	defaultTextMarshaler = TextMarshaler{}
	compactTextMarshaler = TextMarshaler{Compact: true}
)

MarshalText writes the proto text format of m to w.

func MarshalText(w io.Writer, m Message) error { return defaultTextMarshaler.Marshal(w, m) }

MarshalTextString returns a proto text formatted string of m.

func MarshalTextString(m Message) string { return defaultTextMarshaler.Text(m) }

CompactText writes the compact proto text format of m to w.

func CompactText(w io.Writer, m Message) error { return compactTextMarshaler.Marshal(w, m) }

CompactTextString returns a compact proto text formatted string of m.

func CompactTextString(m Message) string { return compactTextMarshaler.Text(m) }

var (
	newline         = []byte("\n")
	endBraceNewline = []byte("}\n")
	posInf          = []byte("inf")
	negInf          = []byte("-inf")
	nan             = []byte("nan")
)

textWriter is an io.Writer that tracks its indentation level.

type textWriter struct {
	compact   bool // same as TextMarshaler.Compact
	expandAny bool // same as TextMarshaler.ExpandAny
	complete  bool // whether the current position is a complete line
	indent    int  // indentation level; never negative
	buf       []byte
}

func (w *textWriter) Write(p []byte) (n int, _ error) {
	newlines := bytes.Count(p, newline)
	if newlines == 0 {
		if !w.compact && w.complete {
			w.writeIndent()
		}
		w.buf = append(w.buf, p...)
		w.complete = false
		return len(p), nil
	}

	frags := bytes.SplitN(p, newline, newlines+1)
	if w.compact {
		for i, frag := range frags {
			if i > 0 {
				w.buf = append(w.buf, ' ')
				n++
			}
			w.buf = append(w.buf, frag...)
			n += len(frag)
		}
		return n, nil
	}

	for i, frag := range frags {
		if w.complete {
			w.writeIndent()
		}
		w.buf = append(w.buf, frag...)
		n += len(frag)
		if i+1 < len(frags) {
			w.buf = append(w.buf, '\n')
			n++
		}
	}
	w.complete = len(frags[len(frags)-1]) == 0
	return n, nil
}

func (w *textWriter) WriteByte(c byte) error {
	if w.compact && c == '\n' {
		c = ' '
	}
	if !w.compact && w.complete {
		w.writeIndent()
	}
	w.buf = append(w.buf, c)
	w.complete = c == '\n'
	return nil
}

func (w *textWriter) writeName(fd protoreflect.FieldDescriptor) {
	if !w.compact && w.complete {
		w.writeIndent()
	}
	w.complete = false

	if fd.Kind() != protoreflect.GroupKind {
		w.buf = append(w.buf, fd.Name()...)
		w.WriteByte(':')

Use message type name for group field name.

		w.buf = append(w.buf, fd.Message().Name()...)
	}

	if !w.compact {
		w.WriteByte(' ')
	}
}

When type URL contains any characters except [0-9A-Za-z./\-]*, it must be quoted.

	for _, ch := range u {
		switch {
		case ch == '.' || ch == '/' || ch == '_':
			continue
		case '0' <= ch && ch <= '9':
			continue
		case 'A' <= ch && ch <= 'Z':
			continue
		case 'a' <= ch && ch <= 'z':
			continue
		default:
			return true
		}
	}
	return false
}

writeProto3Any writes an expanded google.protobuf.Any message. It returns (false, nil) if sv value can't be unmarshaled (e.g. because required messages are not linked in). It returns (true, error) when sv was written in expanded format or an error was encountered.

func (w *textWriter) writeProto3Any(m protoreflect.Message) (bool, error) {
	md := m.Descriptor()
	fdURL := md.Fields().ByName("type_url")
	fdVal := md.Fields().ByName("value")

	url := m.Get(fdURL).String()
	mt, err := protoregistry.GlobalTypes.FindMessageByURL(url)
	if err != nil {
		return false, nil
	}

	b := m.Get(fdVal).Bytes()
	m2 := mt.New()
	if err := proto.Unmarshal(b, m2.Interface()); err != nil {
		return false, nil
	}
	w.Write([]byte("["))
	if requiresQuotes(url) {
		w.writeQuotedString(url)
	} else {
		w.Write([]byte(url))
	}
	if w.compact {
		w.Write([]byte("]:<"))
	} else {
		w.Write([]byte("]: <\n"))
		w.indent++
	}
	if err := w.writeMessage(m2); err != nil {
		return true, err
	}
	if w.compact {
		w.Write([]byte("> "))
	} else {
		w.indent--
		w.Write([]byte(">\n"))
	}
	return true, nil
}

func (w *textWriter) writeMessage(m protoreflect.Message) error {
	md := m.Descriptor()
	if w.expandAny && md.FullName() == "google.protobuf.Any" {
		if canExpand, err := w.writeProto3Any(m); canExpand {
			return err
		}
	}

	fds := md.Fields()
	for i := 0; i < fds.Len(); {
		fd := fds.Get(i)
		if od := fd.ContainingOneof(); od != nil {
			fd = m.WhichOneof(od)
			i += od.Fields().Len()
		} else {
			i++
		}
		if fd == nil || !m.Has(fd) {
			continue
		}

		switch {
		case fd.IsList():
			lv := m.Get(fd).List()
			for j := 0; j < lv.Len(); j++ {
				w.writeName(fd)
				v := lv.Get(j)
				if err := w.writeSingularValue(v, fd); err != nil {
					return err
				}
				w.WriteByte('\n')
			}
		case fd.IsMap():
			kfd := fd.MapKey()
			vfd := fd.MapValue()
			mv := m.Get(fd).Map()

			type entry struct{ key, val protoreflect.Value }
			var entries []entry
			mv.Range(func(k protoreflect.MapKey, v protoreflect.Value) bool {
				entries = append(entries, entry{k.Value(), v})
				return true
			})
			sort.Slice(entries, func(i, j int) bool {
				switch kfd.Kind() {
				case protoreflect.BoolKind:
					return !entries[i].key.Bool() && entries[j].key.Bool()
				case protoreflect.Int32Kind, protoreflect.Sint32Kind, protoreflect.Sfixed32Kind, protoreflect.Int64Kind, protoreflect.Sint64Kind, protoreflect.Sfixed64Kind:
					return entries[i].key.Int() < entries[j].key.Int()
				case protoreflect.Uint32Kind, protoreflect.Fixed32Kind, protoreflect.Uint64Kind, protoreflect.Fixed64Kind:
					return entries[i].key.Uint() < entries[j].key.Uint()
				case protoreflect.StringKind:
					return entries[i].key.String() < entries[j].key.String()
				default:
					panic("invalid kind")
				}
			})
			for _, entry := range entries {
				w.writeName(fd)
				w.WriteByte('<')
				if !w.compact {
					w.WriteByte('\n')
				}
				w.indent++
				w.writeName(kfd)
				if err := w.writeSingularValue(entry.key, kfd); err != nil {
					return err
				}
				w.WriteByte('\n')
				w.writeName(vfd)
				if err := w.writeSingularValue(entry.val, vfd); err != nil {
					return err
				}
				w.WriteByte('\n')
				w.indent--
				w.WriteByte('>')
				w.WriteByte('\n')
			}
		default:
			w.writeName(fd)
			if err := w.writeSingularValue(m.Get(fd), fd); err != nil {
				return err
			}
			w.WriteByte('\n')
		}
	}

	if b := m.GetUnknown(); len(b) > 0 {
		w.writeUnknownFields(b)
	}
	return w.writeExtensions(m)
}

func (w *textWriter) writeSingularValue(v protoreflect.Value, fd protoreflect.FieldDescriptor) error {
	switch fd.Kind() {
	case protoreflect.FloatKind, protoreflect.DoubleKind:
		switch vf := v.Float(); {
		case math.IsInf(vf, +1):
			w.Write(posInf)
		case math.IsInf(vf, -1):
			w.Write(negInf)
		case math.IsNaN(vf):
			w.Write(nan)
		default:
			fmt.Fprint(w, v.Interface())
		}

NOTE: This does not validate UTF-8 for historical reasons.

		w.writeQuotedString(string(v.String()))
	case protoreflect.BytesKind:
		w.writeQuotedString(string(v.Bytes()))
	case protoreflect.MessageKind, protoreflect.GroupKind:
		var bra, ket byte = '<', '>'
		if fd.Kind() == protoreflect.GroupKind {
			bra, ket = '{', '}'
		}
		w.WriteByte(bra)
		if !w.compact {
			w.WriteByte('\n')
		}
		w.indent++
		m := v.Message()
		if m2, ok := m.Interface().(encoding.TextMarshaler); ok {
			b, err := m2.MarshalText()
			if err != nil {
				return err
			}
			w.Write(b)
		} else {
			w.writeMessage(m)
		}
		w.indent--
		w.WriteByte(ket)
	case protoreflect.EnumKind:
		if ev := fd.Enum().Values().ByNumber(v.Enum()); ev != nil {
			fmt.Fprint(w, ev.Name())
		} else {
			fmt.Fprint(w, v.Enum())
		}
	default:
		fmt.Fprint(w, v.Interface())
	}
	return nil
}

writeQuotedString writes a quoted string in the protocol buffer text format.

func (w *textWriter) writeQuotedString(s string) {
	w.WriteByte('"')
	for i := 0; i < len(s); i++ {
		switch c := s[i]; c {
		case '\n':
			w.buf = append(w.buf, `\n`...)
		case '\r':
			w.buf = append(w.buf, `\r`...)
		case '\t':
			w.buf = append(w.buf, `\t`...)
		case '"':
			w.buf = append(w.buf, `\"`...)
		case '\\':
			w.buf = append(w.buf, `\\`...)
		default:
			if isPrint := c >= 0x20 && c < 0x7f; isPrint {
				w.buf = append(w.buf, c)
			} else {
				w.buf = append(w.buf, fmt.Sprintf(`\%03o`, c)...)
			}
		}
	}
	w.WriteByte('"')
}

func (w *textWriter) writeUnknownFields(b []byte) {
	if !w.compact {
		fmt.Fprintf(w, "/* %d unknown bytes */\n", len(b))
	}

	for len(b) > 0 {
		num, wtyp, n := protowire.ConsumeTag(b)
		if n < 0 {
			return
		}
		b = b[n:]

		if wtyp == protowire.EndGroupType {
			w.indent--
			w.Write(endBraceNewline)
			continue
		}
		fmt.Fprint(w, num)
		if wtyp != protowire.StartGroupType {
			w.WriteByte(':')
		}
		if !w.compact || wtyp == protowire.StartGroupType {
			w.WriteByte(' ')
		}
		switch wtyp {
		case protowire.VarintType:
			v, n := protowire.ConsumeVarint(b)
			if n < 0 {
				return
			}
			b = b[n:]
			fmt.Fprint(w, v)
		case protowire.Fixed32Type:
			v, n := protowire.ConsumeFixed32(b)
			if n < 0 {
				return
			}
			b = b[n:]
			fmt.Fprint(w, v)
		case protowire.Fixed64Type:
			v, n := protowire.ConsumeFixed64(b)
			if n < 0 {
				return
			}
			b = b[n:]
			fmt.Fprint(w, v)
		case protowire.BytesType:
			v, n := protowire.ConsumeBytes(b)
			if n < 0 {
				return
			}
			b = b[n:]
			fmt.Fprintf(w, "%q", v)
		case protowire.StartGroupType:
			w.WriteByte('{')
			w.indent++
		default:
			fmt.Fprintf(w, "/* unknown wire type %d */", wtyp)
		}
		w.WriteByte('\n')
	}
}

writeExtensions writes all the extensions in m.

func (w *textWriter) writeExtensions(m protoreflect.Message) error {
	md := m.Descriptor()
	if md.ExtensionRanges().Len() == 0 {
		return nil
	}

	type ext struct {
		desc protoreflect.FieldDescriptor
		val  protoreflect.Value
	}
	var exts []ext
	m.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
		if fd.IsExtension() {
			exts = append(exts, ext{fd, v})
		}
		return true
	})
	sort.Slice(exts, func(i, j int) bool {
		return exts[i].desc.Number() < exts[j].desc.Number()
	})

For message set, use the name of the message as the extension name.

		name := string(ext.desc.FullName())
		if isMessageSet(ext.desc.ContainingMessage()) {
			name = strings.TrimSuffix(name, ".message_set_extension")
		}

		if !ext.desc.IsList() {
			if err := w.writeSingularExtension(name, ext.val, ext.desc); err != nil {
				return err
			}
		} else {
			lv := ext.val.List()
			for i := 0; i < lv.Len(); i++ {
				if err := w.writeSingularExtension(name, lv.Get(i), ext.desc); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func (w *textWriter) writeSingularExtension(name string, v protoreflect.Value, fd protoreflect.FieldDescriptor) error {
	fmt.Fprintf(w, "[%s]:", name)
	if !w.compact {
		w.WriteByte(' ')
	}
	if err := w.writeSingularValue(v, fd); err != nil {
		return err
	}
	w.WriteByte('\n')
	return nil
}

func (w *textWriter) writeIndent() {
	if !w.complete {
		return
	}
	for i := 0; i < w.indent*2; i++ {
		w.buf = append(w.buf, ' ')
	}
	w.complete = false