CSV::Parser::InputsScanner#read_chunk

# File tmp/rubies/ruby-3.0.5/lib/csv/parser.rb, line 206
def read_chunk
  return false if @last_scanner

  unless @keeps.empty?
    keep = @keeps.last
    keep_start = keep[0]
    string = @scanner.string
    keep_data = string.byteslice(keep_start, @scanner.pos - keep_start)
    if keep_data
      keep_buffer = keep[1]
      if keep_buffer
        keep_buffer << keep_data
      else
        keep[1] = keep_data.dup
      end
    end
    keep[0] = 0
  end

  input = @inputs.first
  case input
  when StringIO
    string = input.read
    raise InvalidEncoding unless string.valid_encoding?
    @scanner = StringScanner.new(string)
    @inputs.shift
    @last_scanner = @inputs.empty?
    true
  else
    chunk = input.gets(nil, @chunk_size)
    if chunk
      raise InvalidEncoding unless chunk.valid_encoding?
      @scanner = StringScanner.new(chunk)
      if input.respond_to?(:eof?) and input.eof?
        @inputs.shift
        @last_scanner = @inputs.empty?
      end
      true
    else
      @scanner = StringScanner.new("".encode(@encoding))
      @inputs.shift
      @last_scanner = @inputs.empty?
      if @last_scanner
        false
      else
        read_chunk
      end
    end
  end
end