// Len returns the number of bytes of the unread portion of the
// string.
func (r *Reader) Len() int {
	if r.i >= int64(len(r.s)) {
		return 0
	}
	return int(int64(len(r.s)) - r.i)
}

// Size returns the original length of the underlying string.
// Size is the number of bytes available for reading via [Reader.ReadAt].
// The returned value is always the same and is not affected by calls
// to any other method.

	if checksum != z.digest.Sum32() {
		z.err = ErrChecksum
		return n, z.err
	}
	return n, io.EOF
}

// Calling Close does not close the wrapped [io.Reader] originally passed to [NewReader].
// In order for the ZLIB checksum to be verified, the reader must be
// fully consumed until the [io.EOF].
func (z *reader) Close() error {
	if z.err != nil && z.err != io.EOF {
		return z.err