# Scan a sequence of characters with code `delimiter_char`
	#
	# Return information about the number of delimiters and whether they are positioned
	# such as they can open and/or close emphasis or strong emphasis.
	private fun scan_delimiters(delimiter_processor: MdDelimiterProcessor, delimiter_char: Char): nullable MdDelimiterData do
		var start_index = index
		var start_column = column

		var delimiter_count = 0
		while peek == delimiter_char do
			delimiter_count += 1
			advance 1
		end

		if delimiter_count < delimiter_processor.min_length then
			index = start_index
			column = start_column
			return null
		end

		var before = "\n"
		if start_index > 0 then
			before = input.substring(start_index - 1, 1)
		end

		var char_after = peek
		var after = "\n"
		if char_after != '\0' then
			after = char_after.to_s
		end

		var before_is_punctuation = before.has(re_punctuation)
		var before_is_whitespace = before.has(re_whitespace_char)
		var after_is_punctuation = after.has(re_punctuation)
		var after_is_whitespace = after.has(re_whitespace_char)

		var left_flanking = not after_is_whitespace and
			(not after_is_punctuation or before_is_whitespace or before_is_punctuation)
		var right_flanking = not before_is_whitespace and
			(not before_is_punctuation or after_is_whitespace or after_is_punctuation)

		var can_open
		var can_close
		if delimiter_char == '_' then
			can_open = left_flanking and (not right_flanking or before_is_punctuation)
			can_close = right_flanking and (not left_flanking or after_is_punctuation)
		else
			can_open = left_flanking and delimiter_char == delimiter_processor.opening_delimiter
			can_close = right_flanking and delimiter_char == delimiter_processor.closing_delimiter
		end

		index = start_index
		column = start_column
		return new MdDelimiterData(delimiter_count, can_open, can_close)
	end