Matteo Scandolo | a428586 | 2020-12-01 18:10:10 -0800 | [diff] [blame] | 1 | // Copyright 2019 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Package messageset encodes and decodes the obsolete MessageSet wire format. |
| 6 | package messageset |
| 7 | |
| 8 | import ( |
| 9 | "math" |
| 10 | |
| 11 | "google.golang.org/protobuf/encoding/protowire" |
| 12 | "google.golang.org/protobuf/internal/errors" |
| 13 | pref "google.golang.org/protobuf/reflect/protoreflect" |
| 14 | preg "google.golang.org/protobuf/reflect/protoregistry" |
| 15 | ) |
| 16 | |
| 17 | // The MessageSet wire format is equivalent to a message defiend as follows, |
| 18 | // where each Item defines an extension field with a field number of 'type_id' |
| 19 | // and content of 'message'. MessageSet extensions must be non-repeated message |
| 20 | // fields. |
| 21 | // |
| 22 | // message MessageSet { |
| 23 | // repeated group Item = 1 { |
| 24 | // required int32 type_id = 2; |
| 25 | // required string message = 3; |
| 26 | // } |
| 27 | // } |
| 28 | const ( |
| 29 | FieldItem = protowire.Number(1) |
| 30 | FieldTypeID = protowire.Number(2) |
| 31 | FieldMessage = protowire.Number(3) |
| 32 | ) |
| 33 | |
| 34 | // ExtensionName is the field name for extensions of MessageSet. |
| 35 | // |
| 36 | // A valid MessageSet extension must be of the form: |
| 37 | // message MyMessage { |
| 38 | // extend proto2.bridge.MessageSet { |
| 39 | // optional MyMessage message_set_extension = 1234; |
| 40 | // } |
| 41 | // ... |
| 42 | // } |
| 43 | const ExtensionName = "message_set_extension" |
| 44 | |
| 45 | // IsMessageSet returns whether the message uses the MessageSet wire format. |
| 46 | func IsMessageSet(md pref.MessageDescriptor) bool { |
| 47 | xmd, ok := md.(interface{ IsMessageSet() bool }) |
| 48 | return ok && xmd.IsMessageSet() |
| 49 | } |
| 50 | |
| 51 | // IsMessageSetExtension reports this field extends a MessageSet. |
| 52 | func IsMessageSetExtension(fd pref.FieldDescriptor) bool { |
| 53 | if fd.Name() != ExtensionName { |
| 54 | return false |
| 55 | } |
| 56 | if fd.FullName().Parent() != fd.Message().FullName() { |
| 57 | return false |
| 58 | } |
| 59 | return IsMessageSet(fd.ContainingMessage()) |
| 60 | } |
| 61 | |
| 62 | // FindMessageSetExtension locates a MessageSet extension field by name. |
| 63 | // In text and JSON formats, the extension name used is the message itself. |
| 64 | // The extension field name is derived by appending ExtensionName. |
| 65 | func FindMessageSetExtension(r preg.ExtensionTypeResolver, s pref.FullName) (pref.ExtensionType, error) { |
| 66 | name := s.Append(ExtensionName) |
| 67 | xt, err := r.FindExtensionByName(name) |
| 68 | if err != nil { |
| 69 | if err == preg.NotFound { |
| 70 | return nil, err |
| 71 | } |
| 72 | return nil, errors.Wrap(err, "%q", name) |
| 73 | } |
| 74 | if !IsMessageSetExtension(xt.TypeDescriptor()) { |
| 75 | return nil, preg.NotFound |
| 76 | } |
| 77 | return xt, nil |
| 78 | } |
| 79 | |
| 80 | // SizeField returns the size of a MessageSet item field containing an extension |
| 81 | // with the given field number, not counting the contents of the message subfield. |
| 82 | func SizeField(num protowire.Number) int { |
| 83 | return 2*protowire.SizeTag(FieldItem) + protowire.SizeTag(FieldTypeID) + protowire.SizeVarint(uint64(num)) |
| 84 | } |
| 85 | |
| 86 | // Unmarshal parses a MessageSet. |
| 87 | // |
| 88 | // It calls fn with the type ID and value of each item in the MessageSet. |
| 89 | // Unknown fields are discarded. |
| 90 | // |
| 91 | // If wantLen is true, the item values include the varint length prefix. |
| 92 | // This is ugly, but simplifies the fast-path decoder in internal/impl. |
| 93 | func Unmarshal(b []byte, wantLen bool, fn func(typeID protowire.Number, value []byte) error) error { |
| 94 | for len(b) > 0 { |
| 95 | num, wtyp, n := protowire.ConsumeTag(b) |
| 96 | if n < 0 { |
| 97 | return protowire.ParseError(n) |
| 98 | } |
| 99 | b = b[n:] |
| 100 | if num != FieldItem || wtyp != protowire.StartGroupType { |
| 101 | n := protowire.ConsumeFieldValue(num, wtyp, b) |
| 102 | if n < 0 { |
| 103 | return protowire.ParseError(n) |
| 104 | } |
| 105 | b = b[n:] |
| 106 | continue |
| 107 | } |
| 108 | typeID, value, n, err := ConsumeFieldValue(b, wantLen) |
| 109 | if err != nil { |
| 110 | return err |
| 111 | } |
| 112 | b = b[n:] |
| 113 | if typeID == 0 { |
| 114 | continue |
| 115 | } |
| 116 | if err := fn(typeID, value); err != nil { |
| 117 | return err |
| 118 | } |
| 119 | } |
| 120 | return nil |
| 121 | } |
| 122 | |
| 123 | // ConsumeFieldValue parses b as a MessageSet item field value until and including |
| 124 | // the trailing end group marker. It assumes the start group tag has already been parsed. |
| 125 | // It returns the contents of the type_id and message subfields and the total |
| 126 | // item length. |
| 127 | // |
| 128 | // If wantLen is true, the returned message value includes the length prefix. |
| 129 | func ConsumeFieldValue(b []byte, wantLen bool) (typeid protowire.Number, message []byte, n int, err error) { |
| 130 | ilen := len(b) |
| 131 | for { |
| 132 | num, wtyp, n := protowire.ConsumeTag(b) |
| 133 | if n < 0 { |
| 134 | return 0, nil, 0, protowire.ParseError(n) |
| 135 | } |
| 136 | b = b[n:] |
| 137 | switch { |
| 138 | case num == FieldItem && wtyp == protowire.EndGroupType: |
| 139 | if wantLen && len(message) == 0 { |
| 140 | // The message field was missing, which should never happen. |
| 141 | // Be prepared for this case anyway. |
| 142 | message = protowire.AppendVarint(message, 0) |
| 143 | } |
| 144 | return typeid, message, ilen - len(b), nil |
| 145 | case num == FieldTypeID && wtyp == protowire.VarintType: |
| 146 | v, n := protowire.ConsumeVarint(b) |
| 147 | if n < 0 { |
| 148 | return 0, nil, 0, protowire.ParseError(n) |
| 149 | } |
| 150 | b = b[n:] |
| 151 | if v < 1 || v > math.MaxInt32 { |
| 152 | return 0, nil, 0, errors.New("invalid type_id in message set") |
| 153 | } |
| 154 | typeid = protowire.Number(v) |
| 155 | case num == FieldMessage && wtyp == protowire.BytesType: |
| 156 | m, n := protowire.ConsumeBytes(b) |
| 157 | if n < 0 { |
| 158 | return 0, nil, 0, protowire.ParseError(n) |
| 159 | } |
| 160 | if message == nil { |
| 161 | if wantLen { |
| 162 | message = b[:n:n] |
| 163 | } else { |
| 164 | message = m[:len(m):len(m)] |
| 165 | } |
| 166 | } else { |
| 167 | // This case should never happen in practice, but handle it for |
| 168 | // correctness: The MessageSet item contains multiple message |
| 169 | // fields, which need to be merged. |
| 170 | // |
| 171 | // In the case where we're returning the length, this becomes |
| 172 | // quite inefficient since we need to strip the length off |
| 173 | // the existing data and reconstruct it with the combined length. |
| 174 | if wantLen { |
| 175 | _, nn := protowire.ConsumeVarint(message) |
| 176 | m0 := message[nn:] |
| 177 | message = nil |
| 178 | message = protowire.AppendVarint(message, uint64(len(m0)+len(m))) |
| 179 | message = append(message, m0...) |
| 180 | message = append(message, m...) |
| 181 | } else { |
| 182 | message = append(message, m...) |
| 183 | } |
| 184 | } |
| 185 | b = b[n:] |
| 186 | default: |
| 187 | // We have no place to put it, so we just ignore unknown fields. |
| 188 | n := protowire.ConsumeFieldValue(num, wtyp, b) |
| 189 | if n < 0 { |
| 190 | return 0, nil, 0, protowire.ParseError(n) |
| 191 | } |
| 192 | b = b[n:] |
| 193 | } |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | // AppendFieldStart appends the start of a MessageSet item field containing |
| 198 | // an extension with the given number. The caller must add the message |
| 199 | // subfield (including the tag). |
| 200 | func AppendFieldStart(b []byte, num protowire.Number) []byte { |
| 201 | b = protowire.AppendTag(b, FieldItem, protowire.StartGroupType) |
| 202 | b = protowire.AppendTag(b, FieldTypeID, protowire.VarintType) |
| 203 | b = protowire.AppendVarint(b, uint64(num)) |
| 204 | return b |
| 205 | } |
| 206 | |
| 207 | // AppendFieldEnd appends the trailing end group marker for a MessageSet item field. |
| 208 | func AppendFieldEnd(b []byte) []byte { |
| 209 | return protowire.AppendTag(b, FieldItem, protowire.EndGroupType) |
| 210 | } |
| 211 | |
| 212 | // SizeUnknown returns the size of an unknown fields section in MessageSet format. |
| 213 | // |
| 214 | // See AppendUnknown. |
| 215 | func SizeUnknown(unknown []byte) (size int) { |
| 216 | for len(unknown) > 0 { |
| 217 | num, typ, n := protowire.ConsumeTag(unknown) |
| 218 | if n < 0 || typ != protowire.BytesType { |
| 219 | return 0 |
| 220 | } |
| 221 | unknown = unknown[n:] |
| 222 | _, n = protowire.ConsumeBytes(unknown) |
| 223 | if n < 0 { |
| 224 | return 0 |
| 225 | } |
| 226 | unknown = unknown[n:] |
| 227 | size += SizeField(num) + protowire.SizeTag(FieldMessage) + n |
| 228 | } |
| 229 | return size |
| 230 | } |
| 231 | |
| 232 | // AppendUnknown appends unknown fields to b in MessageSet format. |
| 233 | // |
| 234 | // For historic reasons, unresolved items in a MessageSet are stored in a |
| 235 | // message's unknown fields section in non-MessageSet format. That is, an |
| 236 | // unknown item with typeID T and value V appears in the unknown fields as |
| 237 | // a field with number T and value V. |
| 238 | // |
| 239 | // This function converts the unknown fields back into MessageSet form. |
| 240 | func AppendUnknown(b, unknown []byte) ([]byte, error) { |
| 241 | for len(unknown) > 0 { |
| 242 | num, typ, n := protowire.ConsumeTag(unknown) |
| 243 | if n < 0 || typ != protowire.BytesType { |
| 244 | return nil, errors.New("invalid data in message set unknown fields") |
| 245 | } |
| 246 | unknown = unknown[n:] |
| 247 | _, n = protowire.ConsumeBytes(unknown) |
| 248 | if n < 0 { |
| 249 | return nil, errors.New("invalid data in message set unknown fields") |
| 250 | } |
| 251 | b = AppendFieldStart(b, num) |
| 252 | b = protowire.AppendTag(b, FieldMessage, protowire.BytesType) |
| 253 | b = append(b, unknown[:n]...) |
| 254 | b = AppendFieldEnd(b) |
| 255 | unknown = unknown[n:] |
| 256 | } |
| 257 | return b, nil |
| 258 | } |