tape/dynamic.go

@@ -101,6 +101,7 @@ func EncodeAny(encoder *Encoder, value any, tag Tag) (n int, err error) {
 
 // DecodeAnyInto decodes data and places it into destination, which must be a
 // pointer to a supported type. See [EncodeAny] for a list of supported types.
+// The head of the decoder must be at the start of the payload.
 func DecodeAnyInto(decoder *Decoder, destination any, tag Tag) (n int, err error) {
 	reflectDestination := reflect.ValueOf(destination)
 	if reflectDestination.Kind() != reflect.Pointer {
@@ -110,7 +111,8 @@ func DecodeAnyInto(decoder *Decoder, destination any, tag Tag) (n int, err error
 }
 
 // DecodeAny is like [DecodeAnyInto], but it automatically creates the
-// destination from the tag and data.
+// destination from the tag and data. The head of the decoder must be at the
+// start of the payload.
 func DecodeAny(decoder *Decoder, tag Tag) (value any, n int, err error) {
 	destination, err := skeletonValue(decoder, tag)
 	if err != nil { return nil, n, err }
@@ -128,7 +130,8 @@ var unknownSlicePlaceholderType = reflect.TypeOf(unknownSlicePlaceholder { })
 // decodeAny is internal to [DecodeAny]. It takes in an addressable
 // [reflect.Value] as the destination. If the decoded value cannot fit in the
 // destination, it skims over the payload, leaves the destination empty, and
-// returns without an error.
+// returns without an error. The head of the decoder must be at the start of the
+// payload.
 func decodeAny(decoder *Decoder, destination reflect.Value, tag Tag) (n int, err error) {
 	n, err = decodeAnyOrError(decoder, destination, tag)
 	if _, ok := err.(errCantAssign); ok {
@@ -145,7 +148,7 @@ func decodeAny(decoder *Decoder, destination reflect.Value, tag Tag) (n int, err
 // destination, it decodes nothing and returns an error of type errCantAssign,
 // except for the case of a mismatched OTA element tag, wherein it will skim
 // over the rest of the payload, leave the destination empty, and return without
-// an error.
+// an error. The head of the decoder must be at the start of the payload.
 func decodeAnyOrError(decoder *Decoder, destination reflect.Value, tag Tag) (n int, err error) {
 	err = canSet(destination.Type(), tag)
 	if err != nil { return n, err }
@@ -189,6 +192,13 @@ func decodeAnyOrError(decoder *Decoder, destination reflect.Value, tag Tag) (n i
 		setString(destination, string(buffer))
 	case OTA:
 		// OTA: <length: UN> <elementTag: tape.Tag> <values>*
+		if isTypeAny(destination.Type()) {
+			// need a skeleton value if we are assigning to any.
+			value, err := skeletonValue(decoder, tag)
+			if err != nil { return n, err }
+			destination.Set(value)
+			destination = value.Elem()
+		}
 		length, nn, err := decoder.ReadUintN(tag.CN() + 1)
 		n += nn; if err != nil { return n, err }
 		if length > uint64(MaxStructureLength) {
@@ -356,6 +366,7 @@ func canSet(destination reflect.Type, tag Tag) error {
 			return errCantAssignf("cannot assign float to %v", destination)
 		}
 	case SBA, LBA:
+		if destination.Kind() == reflect.String { return nil }
 		if destination.Kind() != reflect.Slice {
 			return errCantAssignf("cannot assign byte array to %v", destination)
 		}
@@ -463,7 +474,8 @@ func decodeAndSetFloat(decoder *Decoder, destination reflect.Value, bytes int) (
 }
 
 // skeletonValue returns a pointer value. In order for it to be set, it must be
-// dereferenced using Elem().
+// dereferenced using Elem(). The head of the decoder must be at the start of
+// the payload.
 func skeletonValue(decoder *Decoder, tag Tag) (reflect.Value, error) {
 	typ, err := typeOf(decoder, tag)
 	if err != nil { return reflect.Value { }, err }
@@ -471,7 +483,8 @@ func skeletonValue(decoder *Decoder, tag Tag) (reflect.Value, error) {
 }
 
 // typeOf returns the type of the current tag being decoded. It does not use up
-// the decoder, it only peeks.
+// the decoder, it only peeks. The head of the decoder must be at the start of
+// the payload.
 func typeOf(decoder *Decoder, tag Tag) (reflect.Type, error) {
 	switch tag.WithoutCN() {
 	case SI: