fragmenting_writer.go
func (f *writableFragment) finish(hasMoreFragments bool) {
	f.checksumRef.Update(f.checksum.Sum())
	if hasMoreFragments {
		f.flagsRef.Update(hasMoreFragmentsFlag)
	} else {
		f.checksum.Release()
	}
}
func (f *writableFragment) finish(hasMoreFragments bool) {
	f.checksumRef.Update(f.checksum.Sum())
	if hasMoreFragments {
		f.flagsRef.Update(hasMoreFragmentsFlag)
	} else {
		f.checksum.Release()
	}
}
// finish finishes the fragment, updating the final checksum and fragment flags