require "fiddle/import"
class RubyVM::InstructionSequence
  module InternalFunction
    extend Fiddle::Importer
    dlload Fiddle::Handle::DEFAULT

    if Fiddle::SIZEOF_LONG == Fiddle::SIZEOF_VOIDP
      typealias "VALUE", "unsigned long"
    elsif Fiddle::SIZEOF_LONG_LONG == Fiddle::SIZEOF_VOIDP
      typealias "VALUE", "unsigned long long"
    end
    extern "const rb_iseq_t *rb_iseqw_to_iseq(VALUE iseqw)"
    begin
      extern "void rb_iseq_code_location(const rb_iseq_t *iseq, int *first_lineno, int *first_column, int *last_lineno, int *last_column)"
    rescue Fiddle::DLError
      extern "void rb_iseq_code_range(const rb_iseq_t *iseq, int *first_lineno, int *first_column, int *last_lineno, int *last_column)"
      singleton_class.alias_method :rb_iseq_code_location, :rb_iseq_code_range
    end
  end

  def first_column
    code_locations[1]
  end

  def last_lineno
    code_locations[2]
  end

  def last_column
    code_locations[3]
  end

  def code_locations
    size = Fiddle::SIZEOF_INT
    buf = "\0" * (size * 4)
    ptr = Fiddle::Pointer[buf]

    iseq = InternalFunction.rb_iseqw_to_iseq(Fiddle.dlwrap(self))
    InternalFunction.rb_iseq_code_location(iseq, ptr, ptr + size, ptr + size * 2, ptr + size * 3)
    buf.unpack("i4")
  end
end

if $0 == __FILE__
  b1 = ->(){ foo() }; a = 1; b2 = ->(){ bar() }
  p RubyVM::InstructionSequence.of(b1).code_locations
  p RubyVM::InstructionSequence.of(b2).yield_self {|iseq| [iseq.first_lineno, iseq.first_column, iseq.last_lineno, iseq.last_column] }
end