ブロック中のでgotoが使えるメソッド書いてみた

goto.rb

#! ./ruby -I.ext/x86_64-darwin14 --disable-gems
require '-test-/iseq_load/iseq_load'

def spaghetti(&block)
  iseq_data_magic_index         = 0
  iseq_data_major_version_index = 1
  iseq_data_minor_version_index = 2
  iseq_data_format_type_index   = 3
  iseq_data_misc_index          = 4
  iseq_data_label_index         = 5
  iseq_data_path_index          = 6
  iseq_data_absolute_path_index = 7
  iseq_data_first_lineno_index  = 8
  iseq_data_type_index          = 9
  iseq_data_locals_index        = 10
  iseq_data_params_index        = 11
  iseq_data_catch_table_index   = 12
  iseq_data_bytecode_index      = 13

  iseq = RubyVM::InstructionSequence.of(block)

  iseq_data     = iseq.to_a
  old_bytecodes = iseq_data[iseq_data_bytecode_index]
  max_label = old_bytecodes.grep(/^label_/).map{|l|l.to_s.scan(/\d+/)[0].to_i}.max || 0
  labels = {}
  label_of = ->key{
    labels[key] ||= (max_label += 1)
  }
  new_bytecodes = []
  old_bytecodes.map do |code|
    op, arg = code
    if op == :opt_send_without_block && arg[:mid] == :label
      label = new_bytecodes.pop[1]
      label = label[:mid] if Hash === label
      new_bytecodes << "label_#{label_of[label]}".to_sym
    elsif op == :opt_send_without_block && arg[:mid] == :goto
      label = new_bytecodes.pop[1]
      label = label[:mid] if Hash === label
      new_bytecodes << [:jump, "label_#{label_of[label]}".to_sym]
    else
      new_bytecodes << code
    end
  end

  new_iseq_data = iseq_data.dup
  new_iseq_data[iseq_data_bytecode_index] = new_bytecodes

  # topじゃないとevalときエラーになるのでblockをtopに細工
  if new_iseq_data[iseq_data_type_index] == :block
    new_iseq_data[iseq_data_type_index] = :top
  end
  new_iseq = RubyVM::InstructionSequence.iseq_load(new_iseq_data)
  new_iseq.eval
end

spaghetti {
  goto hoge
  label :hoge
  goto :piyo
  label piyo
  max = 1
  label :restart_point
  n = 0
  goto :for_start
  label :for_continue
    n += 1
  label :for_start
  goto :for_end unless n < max
    STDOUT.write n%10
  goto :for_continue
  label :for_end
  puts
  sleep 1
  max += 1
  goto restart_point
}

# 0
# 01
# 012
# 0123
# 01234
# 012345
# 0123456
# 01234567
# 012345678
# 0123456789
# 01234567890