class RDoc::Parser::C

def rb_scan_args(method_body)
  method_body =~ /rb_scan_args\((.*?)\)/m
  return '(*args)' unless $1
  $1.split(/,/)[2] =~ /"(.*?)"/ # format argument
  format = $1.split(//)
  lead = opt = trail = 0
  if format.first =~ /\d/ then
    lead = $&.to_i
    format.shift
    if format.first =~ /\d/ then
      opt = $&.to_i
      format.shift
      if format.first =~ /\d/ then
        trail = $&.to_i
        format.shift
        block_arg = true
      end
    end
  end
  if format.first == '*' and not block_arg then
    var = true
    format.shift
    if format.first =~ /\d/ then
      trail = $&.to_i
      format.shift
    end
  end
  if format.first == ':' then
    hash = true
    format.shift
  end
  if format.first == '&' then
    block = true
    format.shift
  end
  # if the format string is not empty there's a bug in the C code, ignore it
  args = []
  position = 1
  (1...(position + lead)).each do |index|
    args << "p#{index}"
  end
  position += lead
  (position...(position + opt)).each do |index|
    args << "p#{index} = v#{index}"
  end
  position += opt
  if var then
    args << '*args'
    position += 1
  end
  (position...(position + trail)).each do |index|
    args << "p#{index}"
  end
  position += trail
  if hash then
    args << "p#{position} = {}"
  end
  args << '&block' if block
  "(#{args.join ', '})"
end