f.walk(n.Body, ctxSwitch, visit)
	case *ast.TypeSwitchStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(n.Assign, ctxStmt, visit)
		f.walk(n.Body, ctxTypeSwitch, visit)
	case *ast.CommClause:
		f.walk(n.Comm, ctxStmt, visit)
		f.walk(n.Body, ctxStmt, visit)
	case *ast.SelectStmt:
		f.walk(n.Body, ctxStmt, visit)
	case *ast.ForStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(&n.Cond, ctxExpr, visit)

const (
	// Type '0' indicates a regular file.
	TypeReg = '0'

	// Deprecated: Use TypeReg instead.
	TypeRegA = '\x00'

	// Type '1' to '6' are header-only flags and may not have a data body.
	TypeLink    = '1' // Hard link
	TypeSymlink = '2' // Symbolic link
	TypeChar    = '3' // Character device node
	TypeBlock   = '4' // Block device node
	TypeDir     = '5' // Directory
	TypeFifo    = '6' // FIFO node

			}
		}
	}
	r.err = err
	return
}

func (r *checksumReader) Close() error { return r.rc.Close() }

// findBodyOffset does the minimum work to verify the file has a header
// and returns the file body offset.
func (f *File) findBodyOffset() (int64, error) {
	var buf [fileHeaderLen]byte
	if _, err := f.zipr.ReadAt(buf[:], f.headerOffset); err != nil {
		return 0, err
	}
	b := readBuf(buf[:])

	fmtNum(ustar.devMinor(), hdr.Devminor)

	return &tw.blk
}

// writeRawFile writes a minimal file with the given name and flag type.
// It uses format to encode the header format and will write data as the body.
// It uses default values for all of the other fields (as BSD and GNU tar does).
func (tw *Writer) writeRawFile(name, data string, flag byte, format Format) error {
	tw.blk.reset()

	// Best effort for the filename.

	}
	testValidHeader(&h, t)
}

// Issue 4393. It is valid to have an extra data header
// which contains no body.
func TestZeroLengthHeader(t *testing.T) {
	h := FileHeader{
		Name:   "extadata.txt",
		Method: Deflate,
		Extra: []byte{
			85, 84, 5, 0, 3, 154, 144, 195, 77, // tag 21589 size 5

For example, here is a simple complete function definition. The <code>TEXT</code>
directive declares the symbol <code>runtime·profileloop</code> and the instructions
that follow form the body of the function.
The last instruction in a <code>TEXT</code> block must be some sort of jump, usually a <code>RET</code> (pseudo-)instruction.

		}
		if (formats == FormatUnknown) && (err == nil) {
			t.Errorf("test %d, got nil-error, want non-nil error", i)
		}
	}
}

func Benchmark(b *testing.B) {
	type file struct {
		hdr  *Header
		body []byte
	}

	vectors := []struct {
		label string
		files []file
	}{{
		"USTAR",
		[]file{{
			&Header{Name: "bar", Mode: 0640, Size: int64(3)},
			[]byte("foo"),
		}, {