rlp: add Stream.Raw

rlp/decode.go

@@ -540,6 +540,31 @@ func (s *Stream) Bytes() ([]byte, error) {
 	}
 }
 
+// Raw reads a raw encoded value including RLP type information.
+func (s *Stream) Raw() ([]byte, error) {
+	kind, size, err := s.Kind()
+	if err != nil {
+		return nil, err
+	}
+	if kind == Byte {
+		s.kind = -1 // rearm Kind
+		return []byte{s.byteval}, nil
+	}
+	// the original header has already been read and is no longer
+	// available. read content and put a new header in front of it.
+	start := headsize(size)
+	buf := make([]byte, uint64(start)+size)
+	if err := s.readFull(buf[start:]); err != nil {
+		return nil, err
+	}
+	if kind == String {
+		puthead(buf, 0x80, 0xB8, size)
+	} else {
+		puthead(buf, 0xC0, 0xF7, size)
+	}
+	return buf, nil
+}
+
 var errUintOverflow = errors.New("rlp: uint overflow")
 
 // Uint reads an RLP string of up to 8 bytes and returns its contents