CSV::Parser#resolve_row_separator

# File tmp/rubies/ruby-3.1.3/lib/csv/parser.rb, line 676
def resolve_row_separator(separator)
  if separator == :auto
    cr = "\r".encode(@encoding)
    lf = "\n".encode(@encoding)
    if @input.is_a?(StringIO)
      pos = @input.pos
      separator = detect_row_separator(@input.read, cr, lf)
      @input.seek(pos)
    elsif @input.respond_to?(:gets)
      if @input.is_a?(File)
        chunk_size = 32 * 1024
      else
        chunk_size = 1024
      end
      begin
        while separator == :auto
          #
          # if we run out of data, it's probably a single line
          # (ensure will set default value)
          #
          break unless sample = @input.gets(nil, chunk_size)

          # extend sample if we're unsure of the line ending
          if sample.end_with?(cr)
            sample << (@input.gets(nil, 1) || "")
          end

          @samples << sample

          separator = detect_row_separator(sample, cr, lf)
        end
      rescue IOError
        # do nothing:  ensure will set default
      end
    end
    separator = InputRecordSeparator.value if separator == :auto
  end
  separator.to_s.encode(@encoding)
end