// isZip64 reports whether the file size exceeds the 32 bit limit
func (h *FileHeader) isZip64() bool {
	return h.CompressedSize64 >= uint32max || h.UncompressedSize64 >= uint32max
}

func (h *FileHeader) hasDataDescriptor() bool {
	return h.Flags&0x8 != 0
}

func msdosModeToFileMode(m uint32) (mode fs.FileMode) {
	if m&msdosDir != 0 {
		mode = fs.ModeDir | 0777
	} else {
		mode = 0666
	}

	dcomp := f.zip.decompressor(f.Method)
	if dcomp == nil {
		return nil, ErrAlgorithm
	}
	var rc io.ReadCloser = dcomp(r)
	var desr io.Reader
	if f.hasDataDescriptor() {
		desr = io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset+size, dataDescriptorLen)
	}
	rc = &checksumReader{
		rc:   rc,
		hash: crc32.NewIEEE(),
		f:    f,
		desr: desr,
	}