var (
		cntNewline int64
		buf        bytes.Buffer
		blk        block
	)

	// feedTokens copies data in blocks from r into buf until there are
	// at least cnt newlines in buf. It will not read more blocks than needed.
	feedTokens := func(n int64) error {
		for cntNewline < n {
			if _, err := mustReadFull(r, blk[:]); err != nil {
				return err
			}
			buf.Write(blk[:])
			for _, c := range blk {

	var buf []byte
	var directoryEndOffset int64
	for i, bLen := range []int64{1024, 65 * 1024} {
		if bLen > size {
			bLen = size
		}
		buf = make([]byte, int(bLen))
		if _, err := r.ReadAt(buf, size-bLen); err != nil && err != io.EOF {
			return nil, 0, err
		}
		if p := findSignatureInBlock(buf); p >= 0 {
			buf = buf[p:]
			directoryEndOffset = size - bLen + int64(p)

	BucketOptions
	HeaderSize int
}

// Read implements a throttled read
func (r *MonitoredReader) Read(buf []byte) (n int, err error) {
	if r.throttle == nil {
		return r.r.Read(buf)
	}
	if r.lastErr != nil {
		err = r.lastErr
		return
	}
	b := r.throttle.Burst()  // maximum available tokens
	need := len(buf)         // number of bytes requested by caller
	hdr := r.opts.HeaderSize // remaining header bytes

	if skip > 0 {
		n, err := io.ReadFull(r.buf, dst)
		if err != nil && err != io.ErrUnexpectedEOF {
			// If an EOF happens after reading some but not all the bytes,
			// ReadFull returns ErrUnexpectedEOF.
			return dst[:n], err
		}
		dst = dst[:n]
		if err == io.ErrUnexpectedEOF {
			return dst, io.EOF
		}
	}
	// Read until next line.
	in, err := r.buf.ReadBytes('\n')
	dst = append(dst, in...)