vendor/github.com/golang/protobuf/proto/discard.go

   1 // Go support for Protocol Buffers - Google's data interchange format
   2 //
   3 // Copyright 2017 The Go Authors.  All rights reserved.
   4 // https://github.com/golang/protobuf
   5 //
   6 // Redistribution and use in source and binary forms, with or without
   7 // modification, are permitted provided that the following conditions are
   8 // met:
   9 //
  10 //     * Redistributions of source code must retain the above copyright
  11 // notice, this list of conditions and the following disclaimer.
  12 //     * Redistributions in binary form must reproduce the above
  13 // copyright notice, this list of conditions and the following disclaimer
  14 // in the documentation and/or other materials provided with the
  15 // distribution.
  16 //     * Neither the name of Google Inc. nor the names of its
  17 // contributors may be used to endorse or promote products derived from
  18 // this software without specific prior written permission.
  19 //
  20 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  21 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  22 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  23 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  24 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  25 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  26 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  27 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  28 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  30 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31
  32 package proto
  33
  34 import (
  35         "fmt"
  36         "reflect"
  37         "strings"
  38         "sync"
  39         "sync/atomic"
  40 )
  41
  42 type generatedDiscarder interface {
  43         XXX_DiscardUnknown()
  44 }
  45
  46 // DiscardUnknown recursively discards all unknown fields from this message
  47 // and all embedded messages.
  48 //
  49 // When unmarshaling a message with unrecognized fields, the tags and values
  50 // of such fields are preserved in the Message. This allows a later call to
  51 // marshal to be able to produce a message that continues to have those
  52 // unrecognized fields. To avoid this, DiscardUnknown is used to
  53 // explicitly clear the unknown fields after unmarshaling.
  54 //
  55 // For proto2 messages, the unknown fields of message extensions are only
  56 // discarded from messages that have been accessed via GetExtension.
  57 func DiscardUnknown(m Message) {
  58         if m, ok := m.(generatedDiscarder); ok {
  59                 m.XXX_DiscardUnknown()
  60                 return
  61         }
  62         // TODO: Dynamically populate a InternalMessageInfo for legacy messages,
  63         // but the master branch has no implementation for InternalMessageInfo,
  64         // so it would be more work to replicate that approach.
  65         discardLegacy(m)
  66 }
  67
  68 // DiscardUnknown recursively discards all unknown fields.
  69 func (a *InternalMessageInfo) DiscardUnknown(m Message) {
  70         di := atomicLoadDiscardInfo(&a.discard)
  71         if di == nil {
  72                 di = getDiscardInfo(reflect.TypeOf(m).Elem())
  73                 atomicStoreDiscardInfo(&a.discard, di)
  74         }
  75         di.discard(toPointer(&m))
  76 }
  77
  78 type discardInfo struct {
  79         typ reflect.Type
  80
  81         initialized int32 // 0: only typ is valid, 1: everything is valid
  82         lock        sync.Mutex
  83
  84         fields       []discardFieldInfo
  85         unrecognized field
  86 }
  87
  88 type discardFieldInfo struct {
  89         field   field // Offset of field, guaranteed to be valid
  90         discard func(src pointer)
  91 }
  92
  93 var (
  94         discardInfoMap  = map[reflect.Type]*discardInfo{}
  95         discardInfoLock sync.Mutex
  96 )
  97
  98 func getDiscardInfo(t reflect.Type) *discardInfo {
  99         discardInfoLock.Lock()
 100         defer discardInfoLock.Unlock()
 101         di := discardInfoMap[t]
 102         if di == nil {
 103                 di = &discardInfo{typ: t}
 104                 discardInfoMap[t] = di
 105         }
 106         return di
 107 }
 108
 109 func (di *discardInfo) discard(src pointer) {
 110         if src.isNil() {
 111                 return // Nothing to do.
 112         }
 113
 114         if atomic.LoadInt32(&di.initialized) == 0 {
 115                 di.computeDiscardInfo()
 116         }
 117
 118         for _, fi := range di.fields {
 119                 sfp := src.offset(fi.field)
 120                 fi.discard(sfp)
 121         }
 122
 123         // For proto2 messages, only discard unknown fields in message extensions
 124         // that have been accessed via GetExtension.
 125         if em, err := extendable(src.asPointerTo(di.typ).Interface()); err == nil {
 126                 // Ignore lock since DiscardUnknown is not concurrency safe.
 127                 emm, _ := em.extensionsRead()
 128                 for _, mx := range emm {
 129                         if m, ok := mx.value.(Message); ok {
 130                                 DiscardUnknown(m)
 131                         }
 132                 }
 133         }
 134
 135         if di.unrecognized.IsValid() {
 136                 *src.offset(di.unrecognized).toBytes() = nil
 137         }
 138 }
 139
 140 func (di *discardInfo) computeDiscardInfo() {
 141         di.lock.Lock()
 142         defer di.lock.Unlock()
 143         if di.initialized != 0 {
 144                 return
 145         }
 146         t := di.typ
 147         n := t.NumField()
 148
 149         for i := 0; i < n; i++ {
 150                 f := t.Field(i)
 151                 if strings.HasPrefix(f.Name, "XXX_") {
 152                         continue
 153                 }
 154
 155                 dfi := discardFieldInfo{field: toField(&f)}
 156                 tf := f.Type
 157
 158                 // Unwrap tf to get its most basic type.
 159                 var isPointer, isSlice bool
 160                 if tf.Kind() == reflect.Slice && tf.Elem().Kind() != reflect.Uint8 {
 161                         isSlice = true
 162                         tf = tf.Elem()
 163                 }
 164                 if tf.Kind() == reflect.Ptr {
 165                         isPointer = true
 166                         tf = tf.Elem()
 167                 }
 168                 if isPointer && isSlice && tf.Kind() != reflect.Struct {
 169                         panic(fmt.Sprintf("%v.%s cannot be a slice of pointers to primitive types", t, f.Name))
 170                 }
 171
 172                 switch tf.Kind() {
 173                 case reflect.Struct:
 174                         switch {
 175                         case !isPointer:
 176                                 panic(fmt.Sprintf("%v.%s cannot be a direct struct value", t, f.Name))
 177                         case isSlice: // E.g., []*pb.T
 178                                 di := getDiscardInfo(tf)
 179                                 dfi.discard = func(src pointer) {
 180                                         sps := src.getPointerSlice()
 181                                         for _, sp := range sps {
 182                                                 if !sp.isNil() {
 183                                                         di.discard(sp)
 184                                                 }
 185                                         }
 186                                 }
 187                         default: // E.g., *pb.T
 188                                 di := getDiscardInfo(tf)
 189                                 dfi.discard = func(src pointer) {
 190                                         sp := src.getPointer()
 191                                         if !sp.isNil() {
 192                                                 di.discard(sp)
 193                                         }
 194                                 }
 195                         }
 196                 case reflect.Map:
 197                         switch {
 198                         case isPointer || isSlice:
 199                                 panic(fmt.Sprintf("%v.%s cannot be a pointer to a map or a slice of map values", t, f.Name))
 200                         default: // E.g., map[K]V
 201                                 if tf.Elem().Kind() == reflect.Ptr { // Proto struct (e.g., *T)
 202                                         dfi.discard = func(src pointer) {
 203                                                 sm := src.asPointerTo(tf).Elem()
 204                                                 if sm.Len() == 0 {
 205                                                         return
 206                                                 }
 207                                                 for _, key := range sm.MapKeys() {
 208                                                         val := sm.MapIndex(key)
 209                                                         DiscardUnknown(val.Interface().(Message))
 210                                                 }
 211                                         }
 212                                 } else {
 213                                         dfi.discard = func(pointer) {} // Noop
 214                                 }
 215                         }
 216                 case reflect.Interface:
 217                         // Must be oneof field.
 218                         switch {
 219                         case isPointer || isSlice:
 220                                 panic(fmt.Sprintf("%v.%s cannot be a pointer to a interface or a slice of interface values", t, f.Name))
 221                         default: // E.g., interface{}
 222                                 // TODO: Make this faster?
 223                                 dfi.discard = func(src pointer) {
 224                                         su := src.asPointerTo(tf).Elem()
 225                                         if !su.IsNil() {
 226                                                 sv := su.Elem().Elem().Field(0)
 227                                                 if sv.Kind() == reflect.Ptr && sv.IsNil() {
 228                                                         return
 229                                                 }
 230                                                 switch sv.Type().Kind() {
 231                                                 case reflect.Ptr: // Proto struct (e.g., *T)
 232                                                         DiscardUnknown(sv.Interface().(Message))
 233                                                 }
 234                                         }
 235                                 }
 236                         }
 237                 default:
 238                         continue
 239                 }
 240                 di.fields = append(di.fields, dfi)
 241         }
 242
 243         di.unrecognized = invalidField
 244         if f, ok := t.FieldByName("XXX_unrecognized"); ok {
 245                 if f.Type != reflect.TypeOf([]byte{}) {
 246                         panic("expected XXX_unrecognized to be of type []byte")
 247                 }
 248                 di.unrecognized = toField(&f)
 249         }
 250
 251         atomic.StoreInt32(&di.initialized, 1)
 252 }
 253
 254 func discardLegacy(m Message) {
 255         v := reflect.ValueOf(m)
 256         if v.Kind() != reflect.Ptr || v.IsNil() {
 257                 return
 258         }
 259         v = v.Elem()
 260         if v.Kind() != reflect.Struct {
 261                 return
 262         }
 263         t := v.Type()
 264
 265         for i := 0; i < v.NumField(); i++ {
 266                 f := t.Field(i)
 267                 if strings.HasPrefix(f.Name, "XXX_") {
 268                         continue
 269                 }
 270                 vf := v.Field(i)
 271                 tf := f.Type
 272
 273                 // Unwrap tf to get its most basic type.
 274                 var isPointer, isSlice bool
 275                 if tf.Kind() == reflect.Slice && tf.Elem().Kind() != reflect.Uint8 {
 276                         isSlice = true
 277                         tf = tf.Elem()
 278                 }
 279                 if tf.Kind() == reflect.Ptr {
 280                         isPointer = true
 281                         tf = tf.Elem()
 282                 }
 283                 if isPointer && isSlice && tf.Kind() != reflect.Struct {
 284                         panic(fmt.Sprintf("%T.%s cannot be a slice of pointers to primitive types", m, f.Name))
 285                 }
 286
 287                 switch tf.Kind() {
 288                 case reflect.Struct:
 289                         switch {
 290                         case !isPointer:
 291                                 panic(fmt.Sprintf("%T.%s cannot be a direct struct value", m, f.Name))
 292                         case isSlice: // E.g., []*pb.T
 293                                 for j := 0; j < vf.Len(); j++ {
 294                                         discardLegacy(vf.Index(j).Interface().(Message))
 295                                 }
 296                         default: // E.g., *pb.T
 297                                 discardLegacy(vf.Interface().(Message))
 298                         }
 299                 case reflect.Map:
 300                         switch {
 301                         case isPointer || isSlice:
 302                                 panic(fmt.Sprintf("%T.%s cannot be a pointer to a map or a slice of map values", m, f.Name))
 303                         default: // E.g., map[K]V
 304                                 tv := vf.Type().Elem()
 305                                 if tv.Kind() == reflect.Ptr && tv.Implements(protoMessageType) { // Proto struct (e.g., *T)
 306                                         for _, key := range vf.MapKeys() {
 307                                                 val := vf.MapIndex(key)
 308                                                 discardLegacy(val.Interface().(Message))
 309                                         }
 310                                 }
 311                         }
 312                 case reflect.Interface:
 313                         // Must be oneof field.
 314                         switch {
 315                         case isPointer || isSlice:
 316                                 panic(fmt.Sprintf("%T.%s cannot be a pointer to a interface or a slice of interface values", m, f.Name))
 317                         default: // E.g., test_proto.isCommunique_Union interface
 318                                 if !vf.IsNil() && f.Tag.Get("protobuf_oneof") != "" {
 319                                         vf = vf.Elem() // E.g., *test_proto.Communique_Msg
 320                                         if !vf.IsNil() {
 321                                                 vf = vf.Elem()   // E.g., test_proto.Communique_Msg
 322                                                 vf = vf.Field(0) // E.g., Proto struct (e.g., *T) or primitive value
 323                                                 if vf.Kind() == reflect.Ptr {
 324                                                         discardLegacy(vf.Interface().(Message))
 325                                                 }
 326                                         }
 327                                 }
 328                         }
 329                 }
 330         }
 331
 332         if vf := v.FieldByName("XXX_unrecognized"); vf.IsValid() {
 333                 if vf.Type() != reflect.TypeOf([]byte{}) {
 334                         panic("expected XXX_unrecognized to be of type []byte")
 335                 }
 336                 vf.Set(reflect.ValueOf([]byte(nil)))
 337         }
 338
 339         // For proto2 messages, only discard unknown fields in message extensions
 340         // that have been accessed via GetExtension.
 341         if em, err := extendable(m); err == nil {
 342                 // Ignore lock since discardLegacy is not concurrency safe.
 343                 emm, _ := em.extensionsRead()
 344                 for _, mx := range emm {
 345                         if m, ok := mx.value.(Message); ok {
 346                                 discardLegacy(m)
 347                         }
 348                 }
 349         }
 350 }