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,
	}