return string(b[:i])
	}
	return string(b)
}

// formatString copies s into b, NUL-terminating if possible.
func (f *formatter) formatString(b []byte, s string) {
	if len(s) > len(b) {
		f.err = ErrFieldTooLong
	}
	copy(b, s)
	if len(s) < len(b) {
		b[len(s)] = 0
	}

	// Some buggy readers treat regular files with a trailing slash
	// in the V7 path field as a directory even though the full path

		h:    &Header{PAXRecords: map[string]string{"GOLANG.x": strings.Repeat("a", maxSpecialFileSize)}},
	}} {
		w := NewWriter(io.Discard)
		if err := w.WriteHeader(test.h); err != ErrFieldTooLong {
			t.Errorf("%v: w.WriteHeader() = %v, want ErrFieldTooLong", test.name, err)
		}
	}
}

// testNonEmptyWriter wraps an io.Writer and ensures that
// Write is never called with an empty buffer.

			},
			Format: FormatPAX,
		}},
	}, {
		file: "testdata/pax-bad-hdr-file.tar",
		err:  ErrHeader,
	}, {
		file: "testdata/pax-bad-hdr-large.tar.bz2",
		err:  ErrFieldTooLong,
	}, {
		file: "testdata/pax-bad-mtime-file.tar",
		err:  ErrHeader,
	}, {
		file: "testdata/pax-pos-size-file.tar",
		headers: []*Header{{
			Name:     "foo",
			Mode:     0640,