init (PDF::Writer::ARC4)

        # File lib/pdf/writer/arc4.rb, line 28
    28:   def init(key)
    29:     @arc4 = ""
    30:
    31:       # Setup the control array
    32:     return if key.empty?
    33:
    34:     a = []
    35:     (0..255).each { |ii| a[ii] = "%c" % ii }
    36:
    37:     k = (key * 256)[0..255].split(//)
    38:
    39:     jj = 0
    40:     @arc4.each_with_index do |el, ii|
    41:       jj = ((jj + el.to_i) + k[ii].to_i) % 256
    42:       a[ii], a[jj] = a[jj], a[ii]
    43:     end
    44:     @arc4 = a.join
    45:   end