diff --git a/ext/ripper/tools/generate.rb b/ext/ripper/tools/generate.rb
new file mode 100755
index 0000000000..a93d6cd839
--- /dev/null
+++ b/ext/ripper/tools/generate.rb
@@ -0,0 +1,180 @@
+# $Id$
+
+require 'stringio'
+require 'optparse'
+
+def main
+  mode = nil
+  ids1src = nil
+  ids2src = nil
+  template = nil
+  output = nil
+
+  parser = @parser = OptionParser.new
+  parser.banner = "Usage: #{File.basename($0)} --mode=MODE [--ids1src=PATH] [--ids2src=PATH] [--template=PATH] [--output=PATH]"
+  parser.on('--mode=MODE', '"ripper/core" or "eventids1".') {|m|
+    mode = m
+  }
+  parser.on('--ids1src=PATH', 'A source file of event-IDs 1 (parse.y).') {|path|
+    ids1src = path
+  }
+  parser.on('--ids2src=PATH', 'A source file of event-IDs 2 (eventids2.c).') {|path|
+    ids2src = path
+  }
+  parser.on('--template=PATH', 'A template file of ripper/core.rb.') {|path|
+    template = path
+  }
+  parser.on('--output=PATH', 'An output file.') {|path|
+    output = path
+  }
+  parser.on('--help', 'Prints this message and quit.') {
+    puts parser.help
+    exit 0
+  }
+  begin
+    parser.parse!
+  rescue OptionParser::ParseError => err
+    usage err.message
+  end
+  usage 'no mode given' unless mode
+  case mode
+  when 'ripper/core', 'ripper/core.rb'
+    usage 'no --ids1src' unless ids1src
+    usage 'no --ids2src' unless ids2src
+    usage 'no --template' unless template
+    result = generate_ripper_core(template, read_ids1(ids1src), read_ids2(ids2src))
+  when 'eventids1', 'eventids1.c'
+    usage 'no --ids1src' unless ids1src
+    result = generate_eventids1(read_ids1(ids1src))
+  end
+  if output
+    File.open(output, 'w') {|f|
+      f.write result
+    }
+  else
+    puts result
+  end
+end
+
+def usage(msg)
+  $stderr.puts msg
+  $stderr.puts @parser.help
+  exit 1
+end
+
+def generate_ripper_core(template, ids1, ids2)
+  f = StringIO.new
+  f.print <<header
+# This file is automatically generated from #{File.basename(template)} and parse.y.
+# DO NOT MODIFY!!!!!!
+
+header
+  File.foreach(template) do |line|
+    case line
+    when /\A\#include ids1/
+      comma = ''
+      ids1.each do |id, arity|
+        f.print comma; comma = ",\n"
+        f.print "    #{id.intern.inspect} => #{arity}"
+      end
+      f.puts
+    when /\A\#include ids2/
+      comma = ''
+      ids2.each do |id|
+        f.print comma; comma = ",\n"
+        f.print "    #{id.intern.inspect} => 1"
+      end
+      f.puts
+    when /\A\#include handlers1/
+      ids1.each do |id, arity|
+        f.puts
+        f.puts "  def on_#{id}#{paramdecl(arity)}"
+        f.puts "    #{arity == 0 ? 'nil' : 'a'}"
+        f.puts "  end"
+      end
+    when /\A\#include handlers2/
+      ids2.each do |id|
+        f.puts
+        f.puts "  def on_#{id}(token)"
+        f.puts "    token"
+        f.puts "  end"
+      end
+    when /\A\#include (.*)/
+      raise "unknown operation: #include #{$1}"
+    else
+      f.print line
+    end
+  end
+  f.string
+end
+
+def paramdecl(n)
+  return '' if n == 0
+  '(' + ('a'..'z').to_a[0, n].join(', ') + ')'
+end
+
+def generate_eventids1(ids)
+  f = StringIO.new
+  ids.each do |id, arity|
+    f.puts "static ID ripper_id_#{id};"
+  end
+  f.puts
+  f.puts 'static void'
+  f.puts 'ripper_init_eventids1()'
+  f.puts '{'
+  ids.each do |id, arity|
+    f.puts %Q[    ripper_id_#{id} = rb_intern("on_#{id}");]
+  end
+  f.puts '}'
+  f.string
+end
+
+def read_ids1(path)
+  check_arity path
+  ids = {}
+  File.open(path) {|f|
+    f.each do |line|
+      next if /\A\#\s*define\s+s?dispatch/ =~ line
+      next if /ripper_dispatch/ =~ line
+      if a = line.scan(/dispatch(\d)\((\w+)/)
+        a.each do |arity, event|
+          ids[event] = arity.to_i
+        end
+      end
+    end
+  }
+  ids.to_a.sort_by {|event, arity| event.to_s }
+end
+
+def check_arity(path)
+  invalid = false
+  table = {}
+  File.open(path) {|f|
+    File.foreach(path) do |line|
+      next if /\A\#\s*define\s+s?dispatch\d/ =~ line
+      next if /ripper_dispatch\d/ =~ line
+      line.scan(/dispatch(\d)\((\w+)/) do |num, ev|
+        num = num.to_i
+        if table.key?(ev)
+          locations, arity = *table[ev]
+          unless num == arity
+            invalid = true
+            $stderr.puts "arity differ [event=#{ev}]: #{f.lineno}=#{num}; #{locations.join(',')}=#{arity}"
+          end
+          locations.push f.lineno
+        else
+          table[ev] = [[f.lineno], num.to_i]
+        end
+      end
+    end
+  }
+  exit 1 if invalid
+end
+
+def read_ids2(path)
+  File.open(path) {|f|
+    return f.read.scan(/ripper_id_(\w+)/).flatten.uniq.sort
+  }
+end
+
+main