func (tw *Writer) Flush() error {
	if tw.err != nil {
		return tw.err
	}
	if nb := tw.curr.logicalRemaining(); nb > 0 {
		return fmt.Errorf("archive/tar: missed writing %d bytes", nb)
	}
	if _, tw.err = tw.w.Write(zeroBlock[:tw.pad]); tw.err != nil {
		return tw.err
	}
	tw.pad = 0
	return nil
}

// WriteHeader writes hdr and prepares to accept the file's contents.

// blockPadding computes the number of bytes needed to pad offset up to the
// nearest block edge where 0 <= n < blockSize.
func blockPadding(offset int64) (n int64) {
	return -offset & (blockSize - 1)
}

var zeroBlock block

type block [blockSize]byte

// Convert block to any number of formats.
func (b *block) toV7() *headerV7       { return (*headerV7)(b) }
func (b *block) toGNU() *headerGNU     { return (*headerGNU)(b) }

		return nil, nil, err // EOF is okay here; exactly 0 bytes read
	}
	if bytes.Equal(tr.blk[:], zeroBlock[:]) {
		if _, err := io.ReadFull(tr.r, tr.blk[:]); err != nil {
			return nil, nil, err // EOF is okay here; exactly 1 block of zeros read
		}
		if bytes.Equal(tr.blk[:], zeroBlock[:]) {
			return nil, nil, io.EOF // normal EOF; exactly 2 block of zeros read
		}

			t.Errorf("test %d, Header.Size = %d, want %d", i, hdr.Size, v.wantSize)
		}
	}
}

func TestReadGNUSparsePAXHeaders(t *testing.T) {
	padInput := func(s string) string {
		return s + string(zeroBlock[:blockPadding(int64(len(s)))])
	}

	vectors := []struct {
		inputData string
		inputHdrs map[string]string
		wantMap   sparseDatas
		wantSize  int64
		wantName  string
		wantErr   error