gtsocial-umbx

messageset.go (7595B)

---

 // 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"
 	"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 protoreflect.MessageDescriptor) bool {
 	xmd, ok := md.(interface{ IsMessageSet() bool })
 	return ok && xmd.IsMessageSet()
 }
 
 // IsMessageSetExtension reports this field properly extends a MessageSet.
 func IsMessageSetExtension(fd protoreflect.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
 }