check for parsing of the headers so it's not attempted again

flac.go

@@ -64,7 +64,7 @@ type (
 		c io.Closer
 	}
 
-	// Option is a func that modifies Stream and allows detail of the Stream's behaivor to be set.
+	// Option is a func that modifies Stream and allows details of the Stream's behaivor to be set.
 	Option func(s *Stream, r io.Reader) error
 )
 
@@ -91,6 +91,11 @@ func New(r io.Reader, opts ...Option) (stream *Stream, err error) {
 }
 
 func Buffered(stream *Stream, r io.Reader) error {
+	if stream.r != nil {
+		// The initial parsing has already happened
+		return ErrInvalidOption
+	}
+
 	stream.r = bufio.NewReader(r)
 
 	// Verify FLAC signature and parse the StreamInfo metadata block.
@@ -114,12 +119,17 @@ func Buffered(stream *Stream, r io.Reader) error {
 }
 
 func EnableSeek(stream *Stream, r io.Reader) error {
+	if stream.r != nil {
+		// The initial parsing has already happened
+		return ErrInvalidOption
+	}
+
 	rs, ok := r.(io.ReadSeeker)
 	if !ok {
 		return ErrNoSeeker
 	}
 
-	stream.r = rs
+	stream.r = r
 
 	// Verify FLAC signature and parse the StreamInfo metadata block.
 	block, err := stream.parseStreamInfo()
@@ -159,8 +169,9 @@ var (
 	// id3Signature marks the beginning of an ID3 stream, used to skip over ID3 data.
 	id3Signature = []byte("ID3")
 
-	ErrInvalidSeek = errors.New("stream.Seek: out of stream seek")
-	ErrNoSeeker    = errors.New("stream.Seek: no a Seeker")
+	ErrInvalidSeek   = errors.New("stream.Seek: out of stream seek")
+	ErrNoSeeker      = errors.New("stream.Seek: no a Seeker")
+	ErrInvalidOption = errors.New("stream.New: invalid Option")
 )
 
 // parseStreamInfo verifies the signature which marks the beginning of a FLAC