</p>
<pre class="ebnf">
rune_lit         = "'" ( unicode_value | byte_value ) "'" .
unicode_value    = unicode_char | little_u_value | big_u_value | escaped_char .
byte_value       = octal_byte_value | hex_byte_value .
octal_byte_value = `\` octal_digit octal_digit octal_digit .
hex_byte_value   = `\` "x" hex_digit hex_digit .
little_u_value   = `\` "u" hex_digit hex_digit hex_digit hex_digit .

<pre class="ebnf">
rune_lit         = "'" ( unicode_value | byte_value ) "'" .
unicode_value    = unicode_char | little_u_value | big_u_value | escaped_char .
byte_value       = octal_byte_value | hex_byte_value .
octal_byte_value = `\` octal_digit octal_digit octal_digit .
hex_byte_value   = `\` "x" hex_digit hex_digit .
little_u_value   = `\` "u" hex_digit hex_digit hex_digit hex_digit .

			// files generated by a pre-Go1.8 toolchain. If the generated file
			// happened to have a prefix field that parses as valid
			// atime and ctime fields (e.g., when they are valid octal strings),
			// then it is impossible to distinguish between a valid GNU file
			// and an invalid pre-Go1.8 file.
			//
			// See https://golang.org/issues/12594
			// See https://golang.org/issues/21005

}

func TestRoundTrip(t *testing.T) {
	data := []byte("some file contents")

	var b bytes.Buffer
	tw := NewWriter(&b)
	hdr := &Header{
		Name:       "file.txt",
		Uid:        1 << 21, // Too big for 8 octal digits
		Size:       int64(len(data)),
		ModTime:    time.Now().Round(time.Second),
		PAXRecords: map[string]string{"uid": "2097152"},
		Format:     FormatPAX,
		Typeflag:   TypeReg,
	}