Reduce use of binary.Read and, by extention, reflection

internal/metadata/reader.go

@@ -23,14 +23,15 @@ func NewReader(r io.Reader, d decompress.Decompressor) *Reader {
 
 func (r *Reader) advance() error {
 	r.curOffset = 0
-	var size uint16
-	err := binary.Read(r.r, binary.LittleEndian, &size)
+	dat := make([]byte, 2)
+	_, err := r.r.Read(dat)
 	if err != nil {
 		return err
 	}
+	size := binary.LittleEndian.Uint16(dat)
 	realSize := size &^ 0x8000
 	r.dat = make([]byte, realSize)
-	err = binary.Read(r.r, binary.LittleEndian, &r.dat)
+	_, err = r.r.Read(r.dat)
 	if err != nil {
 		return err
 	}