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unmarshal.go
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unmarshal.go
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package protoenc
import (
"encoding"
"errors"
"fmt"
"reflect"
"google.golang.org/protobuf/encoding/protowire"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/types/known/durationpb"
"google.golang.org/protobuf/types/known/structpb"
"google.golang.org/protobuf/types/known/timestamppb"
)
// Unmarshal a protobuf value into a Go value.
// The caller must pass a pointer to the struct to decode into.
func Unmarshal(buf []byte, structPtr interface{}) error {
return unmarshal(buf, structPtr)
}
func unmarshal(buf []byte, structPtr interface{}) (returnErr error) {
defer func() {
if r := recover(); r != nil {
switch e := r.(type) {
case string:
returnErr = errors.New(e)
case error:
returnErr = e
default:
returnErr = errors.New("failed to decode the field")
}
}
}()
if structPtr == nil {
return nil
}
if hasCustomEncoders(reflect.TypeOf(structPtr)) {
return errors.New("custom decoders are not supported for top-level structs, use BinaryUnmarshaler instead")
}
if bu, ok := structPtr.(encoding.BinaryUnmarshaler); ok {
return bu.UnmarshalBinary(buf)
}
val := reflect.ValueOf(structPtr)
if val.Kind() != reflect.Pointer || val.Type().Elem().Kind() != reflect.Struct {
return errors.New("unmarshal takes a pointer to struct")
}
return unmarshalStruct(val.Elem(), buf)
}
func unmarshalStruct(structVal reflect.Value, buf []byte) error {
zeroStructFields(structVal)
structFields, err := StructFields(structVal.Type())
if err != nil {
return err
}
rdr := makeScanner(buf)
for rdr.Scan() {
var field reflect.Value
fieldIndex := findField(structFields, rdr.FieldNum())
if fieldIndex != -1 {
field = initStructField(structVal, structFields[fieldIndex])
}
if err = putValue(field, rdr); err != nil {
if fieldIndex != -1 {
return fmt.Errorf("error while unmarshalling field '%s' of struct '%s.%s': %w",
structFields[fieldIndex].Field.Name,
structVal.Type().PkgPath(),
structVal.Type().Name(),
err)
}
return err
}
}
if err := rdr.Err(); err != nil {
return err
}
return nil
}
func putValue(dst reflect.Value, rdr *scanner) error {
if val, ok := rdr.Primitive(); ok {
err := unmarshalPrimitive(dst, val)
if err != nil {
return fmt.Errorf("error while unmarshalling primitive '%v': %w", val, err)
}
return nil
} else if val, ok := rdr.Complex(); ok {
err := unmarshalBytes(dst, val)
if err != nil {
return fmt.Errorf("error while unmarshalling complex '%v': %w", val, err)
}
return nil
}
panic("unexpected value")
}
func zeroStructFields(val reflect.Value) {
for i := 0; i < val.NumField(); i++ {
field := val.Field(i)
if field.CanSet() {
field.Set(reflect.Zero(field.Type()))
}
}
}
func initStructField(structField reflect.Value, fieldData FieldData) reflect.Value {
index := fieldData.FieldIndex
if len(index) == 0 {
panic(fmt.Errorf("field '%s' has no index", fieldData.Field.Name))
}
var result reflect.Value
for i := range index {
path := index[:i+1]
result = structField.FieldByIndex(path)
if result.Kind() == reflect.Pointer && result.IsNil() {
result.Set(reflect.New(result.Type().Elem()))
}
}
if !result.IsValid() {
panic(fmt.Errorf("field was not initialized"))
}
return result
}
func findField(fields []FieldData, fieldnum protowire.Number) int {
idx := 0
for idx < len(fields) && fields[idx].Num != fieldnum {
idx++
}
if idx == len(fields) {
return -1
}
return idx
}
func tryDecodeFunc(vb []byte, dst reflect.Value) (bool, error) {
dec, ok := decoders.Get(dst.Type())
if !ok {
return false, nil
}
if err := dec(vb, dst); err != nil {
return false, err
}
return true, nil
}
func mapEntry(dstEntry reflect.Value, buf []byte) error {
entryKey := reflect.New(dstEntry.Type().Key()).Elem()
entryVal := reflect.New(dstEntry.Type().Elem()).Elem()
s := makeScanner(buf)
// scan key
if !s.Scan() {
if s.Err() != nil {
return s.Err()
}
return errors.New("map key is missing")
}
if err := putValue(entryKey, s); err != nil {
return fmt.Errorf("failed to unmarshal map key type:'%s': %w", entryKey.Type().String(), err)
}
// scan value
if s.Scan() {
if err := putValue(entryVal, s); err != nil {
return fmt.Errorf("failed to unmarshal map value type:'%s': %w", entryKey.Type().String(), err)
}
}
if s.Err() != nil {
return fmt.Errorf("map scanning failed: %w", s.Err())
}
// scan more and fail if there is more
if s.Scan() {
return errors.New("map entry cannot have several values")
}
if !entryKey.IsValid() || !entryVal.IsValid() {
return errors.New("proto: bad map data: missing key/val")
}
dstEntry.SetMapIndex(entryKey, entryVal)
return nil
}
func unmarshalPrimitive(dst reflect.Value, value primitiveValue) error {
// Value is not settable (invalid reflect.Value, private)
if !dst.CanSet() {
return nil
}
switch dst.Kind() { //nolint:exhaustive
case reflect.Pointer:
if dst.IsNil() {
instantiate(dst)
}
return unmarshalPrimitive(dst.Elem(), value)
case reflect.Bool:
val, err := value.Bool()
if err != nil {
return err
}
dst.SetBool(val)
return nil
case reflect.Int, reflect.Int32, reflect.Int64,
reflect.Int8, reflect.Int16: // Those two are a special case
if dst.Kind() == reflect.Int && dst.Type().Size() < 8 {
return errors.New("detected a 32bit machine, please use either int64 or int32")
}
val, err := value.Int()
if err != nil {
return err
}
dst.SetInt(val)
return nil
case reflect.Uint, reflect.Uint32, reflect.Uint64,
reflect.Uint8, // This is a special case for uint8 kind, []uint8 values will be decoded as protobuf 'bytes'
reflect.Uint16:
if dst.Kind() == reflect.Uint && dst.Type().Size() < 8 {
return errors.New("detected a 32bit machine, please use either uint64 or uint32")
}
val, err := value.Uint()
if err != nil {
return err
}
dst.SetUint(val)
return nil
case reflect.Float32:
val, err := value.Float32()
if err != nil {
return err
}
dst.SetFloat(float64(val))
return nil
case reflect.Float64:
val, err := value.Float64()
if err != nil {
return err
}
dst.SetFloat(val)
return nil
default:
return fmt.Errorf("unsupported primitive kind " + dst.Kind().String())
}
}
// Instantiate an arbitrary type, handling dynamic interface types.
// Returns a Ptr value.
func instantiate(dst reflect.Value) {
dstType := dst.Type().Elem()
dst.Set(reflect.New(dstType))
}
//nolint:cyclop,gocyclo
func unmarshalBytes(dst reflect.Value, value complexValue) (err error) {
defer func() {
if err != nil {
err = fmt.Errorf("failed to unmarshal bytes: %w", err)
}
}()
// Value is not settable (invalid reflect.Value, private)
if !dst.CanSet() {
return nil
}
bytes, err := value.Bytes()
if err != nil {
return fmt.Errorf("bad wiretype for complex types: %w", err)
}
// Check predefined pb types
switch dst.Type() {
case typeTime:
var result timestamppb.Timestamp
err = proto.Unmarshal(bytes, &result)
if err != nil {
return err
}
dst.Set(reflect.ValueOf(result.AsTime()))
return nil
case typeDuration:
var result durationpb.Duration
err = proto.Unmarshal(bytes, &result)
if err != nil {
return err
}
dst.Set(reflect.ValueOf(result.AsDuration()))
return nil
case typeMapInterface:
var result structpb.Struct
err = proto.Unmarshal(bytes, &result)
if err != nil {
return err
}
dst.Set(reflect.ValueOf(result.AsMap()))
return nil
}
switch dst.Kind() { //nolint:exhaustive
case reflect.Pointer:
if dst.IsNil() {
instantiate(dst)
}
// If the pointer is to a struct
if indirect(dst.Type()).Kind() == reflect.Struct {
ok, err := tryDecodeFunc(bytes, dst)
if err != nil {
return err
}
if ok {
return nil
}
}
return unmarshalBytes(dst.Elem(), value)
case reflect.String:
dst.SetString(string(bytes))
return nil
case reflect.Struct:
if ok, err := tryDecodeFunc(bytes, dst); ok {
return nil
} else if err != nil {
return err
}
if enc, ok := dst.Addr().Interface().(encoding.BinaryUnmarshaler); ok {
return enc.UnmarshalBinary(bytes)
}
return unmarshalStruct(dst, bytes)
case reflect.Slice, reflect.Array:
return slice(dst, value)
case reflect.Map:
if dst.IsNil() {
dst.Set(reflect.MakeMap(dst.Type()))
}
return mapEntry(dst, bytes)
default:
return fmt.Errorf("unsupported value kind " + dst.Kind().String())
}
}
func unmarshalByteSeqeunce(dst reflect.Value, val complexValue) error {
unmarshalBytes, err := val.Bytes()
if err != nil {
return err
}
if dst.Kind() == reflect.Array {
if dst.Len() != len(unmarshalBytes) {
return errors.New("array length and buffer length differ")
}
for i := 0; i < dst.Len(); i++ {
// no SetByte method in reflect so has to pass down by uint64
dst.Index(i).SetUint(uint64(unmarshalBytes[i]))
}
} else {
dst.SetBytes(unmarshalBytes)
}
return nil
}
func slice(dst reflect.Value, val complexValue) error {
// TODO: this code doesn't support the case when slice is encoded in several chunks across the message
elemType := dst.Type().Elem()
// we only decode bytes as []byte or [n]byte field
if elemType == typeByte {
err := unmarshalByteSeqeunce(dst, val)
if err != nil {
return err
}
return nil
}
bytes, err := val.Bytes()
if err != nil {
return err
}
ds, ok, err := getDataScannerFor(elemType, bytes)
if err != nil {
return err
}
if !ok { // Other unpacked repeated types
// Just unpack and append one value from buf.
elem := reflect.New(elemType).Elem()
if err = unmarshalBytes(elem, val); err != nil {
return err
}
dst.Set(reflect.Append(dst, elem))
return nil
}
ok, err = tryUnmarshalPredefinedSliceTypes(ds.Wiretype(), bytes, dst)
switch {
case ok:
return nil
case err != nil:
return err
}
sw := sequenceWrapper{
seq: dst,
}
defer sw.FixLen()
// Decode packed values from the buffer and append them to the dst.
for ds.Scan() {
nextElem := sw.NextElem()
value, ok := ds.PrimitiveValue()
if !ok {
return errors.New("incorrect value in packed slice")
}
err := unmarshalPrimitive(nextElem, value)
if err != nil {
return fmt.Errorf("failed to unmarshal slice type '%s': %w", dst.Type(), err)
}
}
return ds.Err()
}
type sequenceWrapper struct {
seq reflect.Value
idx int
}
func (w *sequenceWrapper) NextElem() reflect.Value {
if w.seq.Kind() == reflect.Array {
result := w.seq.Index(w.idx)
w.idx++
return result
}
if sliceCap := w.seq.Cap(); w.idx == sliceCap {
w.seq.Set(grow(w.seq, 1))
}
result := w.seq.Index(w.idx)
w.idx++
return result
}
func (w *sequenceWrapper) FixLen() {
if w.seq.Kind() == reflect.Array {
return
}
w.seq.SetLen(w.idx)
}
// grow grows the slice s so that it can hold extra more values, allocating
// more capacity if needed. It also returns the new cap.
func grow(s reflect.Value, extra int) reflect.Value {
oldLen := s.Len()
newLen := oldLen + extra
if newLen < oldLen {
panic("reflect.Append: slice overflow")
}
targetCap := s.Cap()
if newLen <= targetCap {
return s.Slice(0, targetCap)
}
if targetCap == 0 {
targetCap = extra
} else {
const threshold = 256
for targetCap < newLen {
if oldLen < threshold {
targetCap += targetCap
} else {
targetCap += (targetCap + 3*threshold) / 4
}
}
}
t := reflect.MakeSlice(s.Type(), targetCap, targetCap)
reflect.Copy(t, s)
return t
}