CSV::Parser#prepare_backslash

# File tmp/rubies/ruby-3.3.0/lib/csv/parser.rb, line 494
def prepare_backslash
  return unless @backslash_quote

  @backslash_character = "\\".encode(@encoding)

  @escaped_backslash_character = Regexp.escape(@backslash_character)
  @escaped_backslash = Regexp.new(@escaped_backslash_character)
  if @quote_character.nil?
    @backslash_quote_character = nil
  else
    @backslash_quote_character =
      @backslash_character + @escaped_quote_character
  end
end