# Read `self` between `nstart` and `nend` (excluded) and writte chars to `out`.
	private fun read(out: FlatBuffer, nstart, nend: Int): Int do
		var pos = nstart
		while pos < length and pos < nend do
			out.add self[pos]
			pos += 1
		end
		if pos == length then return -1
		return pos
	end