gitea/vendor/google.golang.org/protobuf/internal/encoding/messageset/messageset.go

242 lines
7.4 KiB
Go

// Copyright 2019 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 messageset encodes and decodes the obsolete MessageSet wire format.
package messageset
import (
"math"
"google.golang.org/protobuf/encoding/protowire"
"google.golang.org/protobuf/internal/errors"
pref "google.golang.org/protobuf/reflect/protoreflect"
)
// The MessageSet wire format is equivalent to a message defined as follows,
// where each Item defines an extension field with a field number of 'type_id'
// and content of 'message'. MessageSet extensions must be non-repeated message
// fields.
//
// message MessageSet {
// repeated group Item = 1 {
// required int32 type_id = 2;
// required string message = 3;
// }
// }
const (
FieldItem = protowire.Number(1)
FieldTypeID = protowire.Number(2)
FieldMessage = protowire.Number(3)
)
// ExtensionName is the field name for extensions of MessageSet.
//
// A valid MessageSet extension must be of the form:
// message MyMessage {
// extend proto2.bridge.MessageSet {
// optional MyMessage message_set_extension = 1234;
// }
// ...
// }
const ExtensionName = "message_set_extension"
// IsMessageSet returns whether the message uses the MessageSet wire format.
func IsMessageSet(md pref.MessageDescriptor) bool {
xmd, ok := md.(interface{ IsMessageSet() bool })
return ok && xmd.IsMessageSet()
}
// IsMessageSetExtension reports this field properly extends a MessageSet.
func IsMessageSetExtension(fd pref.FieldDescriptor) bool {
switch {
case fd.Name() != ExtensionName:
return false
case !IsMessageSet(fd.ContainingMessage()):
return false
case fd.FullName().Parent() != fd.Message().FullName():
return false
}
return true
}
// SizeField returns the size of a MessageSet item field containing an extension
// with the given field number, not counting the contents of the message subfield.
func SizeField(num protowire.Number) int {
return 2*protowire.SizeTag(FieldItem) + protowire.SizeTag(FieldTypeID) + protowire.SizeVarint(uint64(num))
}
// Unmarshal parses a MessageSet.
//
// It calls fn with the type ID and value of each item in the MessageSet.
// Unknown fields are discarded.
//
// If wantLen is true, the item values include the varint length prefix.
// This is ugly, but simplifies the fast-path decoder in internal/impl.
func Unmarshal(b []byte, wantLen bool, fn func(typeID protowire.Number, value []byte) error) error {
for len(b) > 0 {
num, wtyp, n := protowire.ConsumeTag(b)
if n < 0 {
return protowire.ParseError(n)
}
b = b[n:]
if num != FieldItem || wtyp != protowire.StartGroupType {
n := protowire.ConsumeFieldValue(num, wtyp, b)
if n < 0 {
return protowire.ParseError(n)
}
b = b[n:]
continue
}
typeID, value, n, err := ConsumeFieldValue(b, wantLen)
if err != nil {
return err
}
b = b[n:]
if typeID == 0 {
continue
}
if err := fn(typeID, value); err != nil {
return err
}
}
return nil
}
// ConsumeFieldValue parses b as a MessageSet item field value until and including
// the trailing end group marker. It assumes the start group tag has already been parsed.
// It returns the contents of the type_id and message subfields and the total
// item length.
//
// If wantLen is true, the returned message value includes the length prefix.
func ConsumeFieldValue(b []byte, wantLen bool) (typeid protowire.Number, message []byte, n int, err error) {
ilen := len(b)
for {
num, wtyp, n := protowire.ConsumeTag(b)
if n < 0 {
return 0, nil, 0, protowire.ParseError(n)
}
b = b[n:]
switch {
case num == FieldItem && wtyp == protowire.EndGroupType:
if wantLen && len(message) == 0 {
// The message field was missing, which should never happen.
// Be prepared for this case anyway.
message = protowire.AppendVarint(message, 0)
}
return typeid, message, ilen - len(b), nil
case num == FieldTypeID && wtyp == protowire.VarintType:
v, n := protowire.ConsumeVarint(b)
if n < 0 {
return 0, nil, 0, protowire.ParseError(n)
}
b = b[n:]
if v < 1 || v > math.MaxInt32 {
return 0, nil, 0, errors.New("invalid type_id in message set")
}
typeid = protowire.Number(v)
case num == FieldMessage && wtyp == protowire.BytesType:
m, n := protowire.ConsumeBytes(b)
if n < 0 {
return 0, nil, 0, protowire.ParseError(n)
}
if message == nil {
if wantLen {
message = b[:n:n]
} else {
message = m[:len(m):len(m)]
}
} else {
// This case should never happen in practice, but handle it for
// correctness: The MessageSet item contains multiple message
// fields, which need to be merged.
//
// In the case where we're returning the length, this becomes
// quite inefficient since we need to strip the length off
// the existing data and reconstruct it with the combined length.
if wantLen {
_, nn := protowire.ConsumeVarint(message)
m0 := message[nn:]
message = nil
message = protowire.AppendVarint(message, uint64(len(m0)+len(m)))
message = append(message, m0...)
message = append(message, m...)
} else {
message = append(message, m...)
}
}
b = b[n:]
default:
// We have no place to put it, so we just ignore unknown fields.
n := protowire.ConsumeFieldValue(num, wtyp, b)
if n < 0 {
return 0, nil, 0, protowire.ParseError(n)
}
b = b[n:]
}
}
}
// AppendFieldStart appends the start of a MessageSet item field containing
// an extension with the given number. The caller must add the message
// subfield (including the tag).
func AppendFieldStart(b []byte, num protowire.Number) []byte {
b = protowire.AppendTag(b, FieldItem, protowire.StartGroupType)
b = protowire.AppendTag(b, FieldTypeID, protowire.VarintType)
b = protowire.AppendVarint(b, uint64(num))
return b
}
// AppendFieldEnd appends the trailing end group marker for a MessageSet item field.
func AppendFieldEnd(b []byte) []byte {
return protowire.AppendTag(b, FieldItem, protowire.EndGroupType)
}
// SizeUnknown returns the size of an unknown fields section in MessageSet format.
//
// See AppendUnknown.
func SizeUnknown(unknown []byte) (size int) {
for len(unknown) > 0 {
num, typ, n := protowire.ConsumeTag(unknown)
if n < 0 || typ != protowire.BytesType {
return 0
}
unknown = unknown[n:]
_, n = protowire.ConsumeBytes(unknown)
if n < 0 {
return 0
}
unknown = unknown[n:]
size += SizeField(num) + protowire.SizeTag(FieldMessage) + n
}
return size
}
// AppendUnknown appends unknown fields to b in MessageSet format.
//
// For historic reasons, unresolved items in a MessageSet are stored in a
// message's unknown fields section in non-MessageSet format. That is, an
// unknown item with typeID T and value V appears in the unknown fields as
// a field with number T and value V.
//
// This function converts the unknown fields back into MessageSet form.
func AppendUnknown(b, unknown []byte) ([]byte, error) {
for len(unknown) > 0 {
num, typ, n := protowire.ConsumeTag(unknown)
if n < 0 || typ != protowire.BytesType {
return nil, errors.New("invalid data in message set unknown fields")
}
unknown = unknown[n:]
_, n = protowire.ConsumeBytes(unknown)
if n < 0 {
return nil, errors.New("invalid data in message set unknown fields")
}
b = AppendFieldStart(b, num)
b = protowire.AppendTag(b, FieldMessage, protowire.BytesType)
b = append(b, unknown[:n]...)
b = AppendFieldEnd(b)
unknown = unknown[n:]
}
return b, nil
}