require 'dl/import'
module Win32

=begin rdoc
= Win32 Registry

win32/registry is registry accessor library for Win32 platform.
It uses dl/import to call Win32 Registry APIs.

== example
  Win32::Registry::HKEY_CURRENT_USER.open('SOFTWARE\foo') do |reg|
    value = reg['foo']                               # read a value
    value = reg['foo', Win32::Registry::REG_SZ]      # read a value with type
    type, value = reg.read('foo')                    # read a value
    reg['foo'] = 'bar'                               # write a value
    reg['foo', Win32::Registry::REG_SZ] = 'bar'      # write a value with type
    reg.write('foo', Win32::Registry::REG_SZ, 'bar') # write a value

    reg.each_value { |name, type, data| ... }        # Enumerate values
    reg.each_key { |key, wtime| ... }                # Enumerate subkeys

    reg.delete_value(name)                         # Delete a value
    reg.delete_key(name)                           # Delete a subkey
    reg.delete_key(name, true)                     # Delete a subkey recursively
  end

= Reference

== Win32::Registry class

--- info

--- num_keys

--- max_key_length

--- num_values

--- max_value_name_length

--- max_value_length

--- descriptor_length

--- wtime
    Returns an item of key information.

=== constants
--- HKEY_CLASSES_ROOT

--- HKEY_CURRENT_USER

--- HKEY_LOCAL_MACHINE

--- HKEY_PERFORMANCE_DATA

--- HKEY_CURRENT_CONFIG

--- HKEY_DYN_DATA

    Win32::Registry object whose key is predefined key.
For detail, see the MSDN[http://msdn.microsoft.com/library/en-us/sysinfo/base/predefined_keys.asp] article.

=end rdoc

  WCHAR = Encoding::UTF_16LE
  WCHAR_SPACE = "\0".encode(WCHAR).freeze
  LOCALE = Encoding.find(Encoding.locale_charmap)

  class Registry

    #
    # For detail, see the MSDN[http://msdn.microsoft.com/library/en-us/sysinfo/base/registry.asp].
    #
    # --- HKEY_*
    #
    #     Predefined key ((*handle*)).
    #     These are Integer, not Win32::Registry.
    #
    # --- REG_*
    #
    #     Registry value type.
    #
    # --- KEY_*
    #
    #     Security access mask.
    #
    # --- KEY_OPTIONS_*
    #
    #     Key options.
    #
    # --- REG_CREATED_NEW_KEY
    #
    # --- REG_OPENED_EXISTING_KEY
    #
    #     If the key is created newly or opened existing key.
    #     See also Registry#disposition method.
    module Constants
      HKEY_CLASSES_ROOT = 0x80000000
      HKEY_CURRENT_USER = 0x80000001
      HKEY_LOCAL_MACHINE = 0x80000002
      HKEY_USERS = 0x80000003
      HKEY_PERFORMANCE_DATA = 0x80000004
      HKEY_PERFORMANCE_TEXT = 0x80000050
      HKEY_PERFORMANCE_NLSTEXT = 0x80000060
      HKEY_CURRENT_CONFIG = 0x80000005
      HKEY_DYN_DATA = 0x80000006

      REG_NONE = 0
      REG_SZ = 1
      REG_EXPAND_SZ = 2
      REG_BINARY = 3
      REG_DWORD = 4
      REG_DWORD_LITTLE_ENDIAN = 4
      REG_DWORD_BIG_ENDIAN = 5
      REG_LINK = 6
      REG_MULTI_SZ = 7
      REG_RESOURCE_LIST = 8
      REG_FULL_RESOURCE_DESCRIPTOR = 9
      REG_RESOURCE_REQUIREMENTS_LIST = 10
      REG_QWORD = 11
      REG_QWORD_LITTLE_ENDIAN = 11

      STANDARD_RIGHTS_READ = 0x00020000
      STANDARD_RIGHTS_WRITE = 0x00020000
      KEY_QUERY_VALUE = 0x0001
      KEY_SET_VALUE = 0x0002
      KEY_CREATE_SUB_KEY = 0x0004
      KEY_ENUMERATE_SUB_KEYS = 0x0008
      KEY_NOTIFY = 0x0010
      KEY_CREATE_LINK = 0x0020
      KEY_READ = STANDARD_RIGHTS_READ |
        KEY_QUERY_VALUE | KEY_ENUMERATE_SUB_KEYS | KEY_NOTIFY
      KEY_WRITE = STANDARD_RIGHTS_WRITE |
        KEY_SET_VALUE | KEY_CREATE_SUB_KEY
      KEY_EXECUTE = KEY_READ
      KEY_ALL_ACCESS = KEY_READ | KEY_WRITE | KEY_CREATE_LINK

      REG_OPTION_RESERVED = 0x0000
      REG_OPTION_NON_VOLATILE = 0x0000
      REG_OPTION_VOLATILE = 0x0001
      REG_OPTION_CREATE_LINK = 0x0002
      REG_OPTION_BACKUP_RESTORE = 0x0004
      REG_OPTION_OPEN_LINK = 0x0008
      REG_LEGAL_OPTION = REG_OPTION_RESERVED |
        REG_OPTION_NON_VOLATILE | REG_OPTION_CREATE_LINK |
        REG_OPTION_BACKUP_RESTORE | REG_OPTION_OPEN_LINK

      REG_CREATED_NEW_KEY = 1
      REG_OPENED_EXISTING_KEY = 2

      REG_WHOLE_HIVE_VOLATILE = 0x0001
      REG_REFRESH_HIVE = 0x0002
      REG_NO_LAZY_FLUSH = 0x0004
      REG_FORCE_RESTORE = 0x0008

      MAX_KEY_LENGTH = 514
      MAX_VALUE_LENGTH = 32768
    end
    include Constants
    include Enumerable

    #
    # Error
    #
    class Error < ::StandardError
      module Kernel32
        extend DL::Importer
        dlload "kernel32.dll"
      end
      FormatMessageW = Kernel32.extern "int FormatMessageW(int, void *, int, int, void *, int, void *)", :stdcall
      def initialize(code)
        @code = code
        msg = WCHAR_SPACE * 1024
        len = FormatMessageW.call(0x1200, 0, code, 0, msg, 1024, 0)
        msg = msg[0, len].encode
        super msg.tr("\r", '').chomp
      end
      attr_reader :code
    end

    #
    # Predefined Keys
    #
    class PredefinedKey < Registry
      def initialize(hkey, keyname)
        @hkey = hkey
        @parent = nil
        @keyname = keyname
        @disposition = REG_OPENED_EXISTING_KEY
      end

      # Predefined keys cannot be closed
      def close
        raise Error.new(5) ## ERROR_ACCESS_DENIED
      end

      # Fake #class method for Registry#open, Registry#create
      def class
        Registry
      end

      # Make all
      Constants.constants.grep(/^HKEY_/) do |c|
        Registry.const_set c, new(Constants.const_get(c), c.to_s)
      end
    end

    #
    # Win32 APIs
    #
    module API
      extend DL::Importer
      dlload "advapi32.dll"
      [
        "long RegOpenKeyExW(void *, void *, long, long, void *)",
        "long RegCreateKeyExW(void *, void *, long, long, long, long, void *, void *, void *)",
        "long RegEnumValueW(void *, long, void *, void *, void *, void *, void *, void *)",
        "long RegEnumKeyExW(void *, long, void *, void *, void *, void *, void *, void *)",
        "long RegQueryValueExW(void *, void *, void *, void *, void *, void *)",
        "long RegSetValueExW(void *, void *, long, long, void *, long)",
        "long RegDeleteValue(void *, void *)",
        "long RegDeleteKey(void *, void *)",
        "long RegFlushKey(void *)",
        "long RegCloseKey(void *)",
        "long RegQueryInfoKey(void *, void *, void *, void *, void *, void *, void *, void *, void *, void *, void *, void *)",
      ].each do |fn|
        cfunc = extern fn, :stdcall
        const_set cfunc.name.intern, cfunc
      end

      module_function

      def check(result)
        raise Error, result, caller(2) if result != 0
      end

      def packdw(dw)
        [dw].pack('V')
      end

      def unpackdw(dw)
        dw += [0].pack('V')
        dw.unpack('V')[0]
      end

      def packqw(qw)
        [ qw & 0xFFFFFFFF, qw >> 32 ].pack('VV')
      end

      def unpackqw(qw)
        qw = qw.unpack('VV')
        (qw[1] << 32) | qw[0]
      end

      def OpenKey(hkey, name, opt, desired)
        result = packdw(0)
        check RegOpenKeyExW.call(hkey, name.encode(WCHAR), opt, desired, result)
        unpackdw(result)
      end

      def CreateKey(hkey, name, opt, desired)
        result = packdw(0)
        disp = packdw(0)
        check RegCreateKeyExW.call(hkey, name.encode(WCHAR), 0, 0, opt, desired,
                                   0, result, disp)
        [ unpackdw(result), unpackdw(disp) ]
      end

      def EnumValue(hkey, index)
        name = WCHAR_SPACE * Constants::MAX_KEY_LENGTH
        size = packdw(Constants::MAX_KEY_LENGTH)
        check RegEnumValueW.call(hkey, index, name, size, 0, 0, 0, 0)
        name[0, unpackdw(size)].encode
      end

      def EnumKey(hkey, index)
        name = WCHAR_SPACE * Constants::MAX_KEY_LENGTH
        size = packdw(Constants::MAX_KEY_LENGTH)
        wtime = ' ' * 8
        check RegEnumKeyExW.call(hkey, index, name, size, 0, 0, 0, wtime)
        [ name[0, unpackdw(size)].encode, unpackqw(wtime) ]
      end

      def QueryValue(hkey, name)
        type = packdw(0)
        size = packdw(0)
        name = name.encode(WCHAR)
        check RegQueryValueExW.call(hkey, name, 0, type, 0, size)
        data = WCHAR_SPACE * unpackdw(size)
        check RegQueryValueExW.call(hkey, name, 0, type, data, size)
        [ unpackdw(type), data[0, unpackdw(size)].encode ]
      end

      def SetValue(hkey, name, type, data, size)
        case type
        when REG_SZ, REG_EXPAND_SZ, REG_MULTI_SZ
          data = data.encode(WCHAR)
          size ||= data.size + 1
        end
        check RegSetValueExW.call(hkey, name.encode(WCHAR), 0, type, data, size)
      end

      def DeleteValue(hkey, name)
        check RegDeleteValue.call(hkey, name.encode(WCHAR))
      end

      def DeleteKey(hkey, name)
        check RegDeleteKey.call(hkey, name.encode(WCHAR))
      end

      def FlushKey(hkey)
        check RegFlushKey.call(hkey)
      end

      def CloseKey(hkey)
        check RegCloseKey.call(hkey)
      end

      def QueryInfoKey(hkey)
        subkeys = packdw(0)
        maxsubkeylen = packdw(0)
        values = packdw(0)
        maxvaluenamelen = packdw(0)
        maxvaluelen = packdw(0)
        secdescs = packdw(0)
        wtime = ' ' * 8
        check RegQueryInfoKey.call(hkey, 0, 0, 0, subkeys, maxsubkeylen, 0,
          values, maxvaluenamelen, maxvaluelen, secdescs, wtime)
        [ unpackdw(subkeys), unpackdw(maxsubkeylen), unpackdw(values),
          unpackdw(maxvaluenamelen), unpackdw(maxvaluelen),
          unpackdw(secdescs), unpackqw(wtime) ]
      end
    end

    #
    # Replace %\w+% into the environment value of what is contained between the %'s
    # This method is used for REG_EXPAND_SZ.
    #
    # For detail, see expandEnvironmentStrings[http://msdn.microsoft.com/library/en-us/sysinfo/base/expandenvironmentstrings.asp] \Win32 \API.
    #
    def self.expand_environ(str)
      str.gsub(Regexp.compile("%([^%]+)%".encode(str.encoding))) { ENV[$1] || ENV[$1.upcase] || $& }
    end

    @@type2name = { }
    %w[
      REG_NONE REG_SZ REG_EXPAND_SZ REG_BINARY REG_DWORD
      REG_DWORD_BIG_ENDIAN REG_LINK REG_MULTI_SZ
      REG_RESOURCE_LIST REG_FULL_RESOURCE_DESCRIPTOR
      REG_RESOURCE_REQUIREMENTS_LIST REG_QWORD
    ].each do |type|
      @@type2name[Constants.const_get(type)] = type
    end

    #
    # Convert registry type value to readable string.
    #
    def self.type2name(type)
      @@type2name[type] || type.to_s
    end

    #
    # Convert 64-bit FILETIME integer into Time object.
    #
    def self.wtime2time(wtime)
      Time.at((wtime - 116444736000000000) / 10000000)
    end

    #
    # Convert Time object or Integer object into 64-bit FILETIME.
    #
    def self.time2wtime(time)
      time.to_i * 10000000 + 116444736000000000
    end

    #
    # constructor
    #
    private_class_method :new

    #
    # --- Registry.open(key, subkey, desired = KEY_READ, opt = REG_OPTION_RESERVED)
    #
    # --- Registry.open(key, subkey, desired = KEY_READ, opt = REG_OPTION_RESERVED) { |reg| ... }
    #
    # Open the registry key subkey under key.
    # key is Win32::Registry object of parent key.
    # You can use predefined key HKEY_* (see Constants)
    # desired and opt is access mask and key option.
    # For detail, see the MSDN[http://msdn.microsoft.com/library/en-us/sysinfo/base/regopenkeyex.asp].
    # If block is given, the key is closed automatically.
    def self.open(hkey, subkey, desired = KEY_READ, opt = REG_OPTION_RESERVED)
      subkey = subkey.chomp('\\')
      newkey = API.OpenKey(hkey.hkey, subkey, opt, desired)
      obj = new(newkey, hkey, subkey, REG_OPENED_EXISTING_KEY)
      if block_given?
        begin
          yield obj
        ensure
          obj.close
        end
      else
        obj
      end
    end

    #
    # --- Registry.create(key, subkey, desired = KEY_ALL_ACCESS, opt = REG_OPTION_RESERVED)
    #
    # --- Registry.create(key, subkey, desired = KEY_ALL_ACCESS, opt = REG_OPTION_RESERVED) { |reg| ... }
    #
    # Create or open the registry key subkey under key.
    # You can use predefined key HKEY_* (see Constants)
    #
    # If subkey is already exists, key is opened and Registry#created?
    # method will return false.
    #
    # If block is given, the key is closed automatically.
    #
    def self.create(hkey, subkey, desired = KEY_ALL_ACCESS, opt = REG_OPTION_RESERVED)
      newkey, disp = API.CreateKey(hkey.hkey, subkey, opt, desired)
      obj = new(newkey, hkey, subkey, disp)
      if block_given?
        begin
          yield obj
        ensure
          obj.close
        end
      else
        obj
      end
    end

    #
    # finalizer
    #
    @@final = proc { |hkey| proc { API.CloseKey(hkey[0]) if hkey[0] } }

    #
    # initialize
    #
    def initialize(hkey, parent, keyname, disposition)
      @hkey = hkey
      @parent = parent
      @keyname = keyname
      @disposition = disposition
      @hkeyfinal = [ hkey ]
      ObjectSpace.define_finalizer self, @@final.call(@hkeyfinal)
    end

    #  Returns key handle value.
    attr_reader :hkey
    # Win32::Registry object of parent key, or nil if predefeined key.
    attr_reader :parent
    # Same as subkey value of Registry.open or
    # Registry.create method.
    attr_reader :keyname
    #  Disposition value (REG_CREATED_NEW_KEY or REG_OPENED_EXISTING_KEY).
    attr_reader :disposition

    #
    # Returns if key is created ((*newly*)).
    # (see Registry.create) -- basically you call create
    # then when you call created? on the instance returned
    # it will tell if it was successful or not
    #
    def created?
      @disposition == REG_CREATED_NEW_KEY
    end

    #
    # Returns if key is not closed.
    #
    def open?
      !@hkey.nil?
    end

    #
    # Full path of key such as 'HKEY_CURRENT_USER\SOFTWARE\foo\bar'.
    #
    def name
      parent = self
      name = @keyname
      while parent = parent.parent
        name = parent.keyname + '\\' + name
      end
      name
    end

    def inspect
      "\#<Win32::Registry key=#{name.inspect}>"
    end

    #
    # marshalling is not allowed
    #
    def _dump(depth)
      raise TypeError, "can't dump Win32::Registry"
    end

    #
    # Same as Win32::Registry.open (self, subkey, desired, opt)
    #
    def open(subkey, desired = KEY_READ, opt = REG_OPTION_RESERVED, &blk)
      self.class.open(self, subkey, desired, opt, &blk)
    end

    #
    # Same as Win32::Registry.create (self, subkey, desired, opt)
    #
    def create(subkey, desired = KEY_ALL_ACCESS, opt = REG_OPTION_RESERVED, &blk)
      self.class.create(self, subkey, desired, opt, &blk)
    end

    #
    # Close key.
    #
    # After close, most method raise an error.
    #
    def close
      API.CloseKey(@hkey)
      @hkey = @parent = @keyname = nil
      @hkeyfinal[0] = nil
    end

    #
    # Enumerate values.
    #
    def each_value
      index = 0
      while true
        begin
          subkey = API.EnumValue(@hkey, index)
        rescue Error
          break
        end
        begin
          type, data = read(subkey)
        rescue Error
          next
        end
        yield subkey, type, data
        index += 1
      end
      index
    end
    alias each each_value

    #
    # Enumerate subkeys.
    #
    # subkey is String which contains name of subkey.
    # wtime is last write time as FILETIME (64-bit integer).
    # (see Registry.wtime2time)
    #
    def each_key
      index = 0
      while true
        begin
          subkey, wtime = API.EnumKey(@hkey, index)
        rescue Error
          break
        end
        yield subkey, wtime
        index += 1
      end
      index
    end

    #
    # return keys as an array
    #
    def keys
      keys_ary = []
      each_key { |key,| keys_ary << key }
      keys_ary
    end

    # Read a registry value named name and return array of
    # [ type, data ].
    # When name is nil, the `default' value is read.
    # type is value type. (see Win32::Registry::Constants module)
    # data is value data, its class is:
    # :REG_SZ, REG_EXPAND_SZ
    #    String
    # :REG_MULTI_SZ
    #    Array of String
    # :REG_DWORD, REG_DWORD_BIG_ENDIAN, REG_QWORD
    #    Integer
    # :REG_BINARY
    #    String (contains binary data)
    #
    # When rtype is specified, the value type must be included by
    # rtype array, or TypeError is raised.
    def read(name, *rtype)
      type, data = API.QueryValue(@hkey, name)
      unless rtype.empty? or rtype.include?(type)
        raise TypeError, "Type mismatch (expect #{rtype.inspect} but #{type} present)"
      end
      case type
      when REG_SZ, REG_EXPAND_SZ
        [ type, data.chop ]
      when REG_MULTI_SZ
        [ type, data.split(/\0/) ]
      when REG_BINARY
        [ type, data ]
      when REG_DWORD
        [ type, API.unpackdw(data) ]
      when REG_DWORD_BIG_ENDIAN
        [ type, data.unpack('N')[0] ]
      when REG_QWORD
        [ type, API.unpackqw(data) ]
      else
        raise TypeError, "Type #{type} is not supported."
      end
    end

    #
    # Read a registry value named name and return its value data.
    # The class of value is same as #read method returns.
    #
    # If the value type is REG_EXPAND_SZ, returns value data whose environment
    # variables are replaced.
    # If the value type is neither REG_SZ, REG_MULTI_SZ, REG_DWORD,
    # REG_DWORD_BIG_ENDIAN, nor REG_QWORD, TypeError is raised.
    #
    # The meaning of rtype is same as #read method.
    #
    def [](name, *rtype)
      type, data = read(name, *rtype)
      case type
      when REG_SZ, REG_DWORD, REG_QWORD, REG_MULTI_SZ
        data
      when REG_EXPAND_SZ
        Registry.expand_environ(data)
      else
        raise TypeError, "Type #{type} is not supported."
      end
    end

    # Read a REG_SZ(read_s), REG_DWORD(read_i), or REG_BINARY(read_bin)
    # registry value named name.
    #
    # If the values type does not match, TypeError is raised.
    def read_s(name)
      read(name, REG_SZ)[1]
    end

    #
    # Read a REG_SZ or REG_EXPAND_SZ registry value named name.
    #
    # If the value type is REG_EXPAND_SZ, environment variables are replaced.
    # Unless the value type is REG_SZ or REG_EXPAND_SZ, TypeError is raised.
    #
    def read_s_expand(name)
      type, data = read(name, REG_SZ, REG_EXPAND_SZ)
      if type == REG_EXPAND_SZ
        Registry.expand_environ(data)
      else
        data
      end
    end

    #
    # Read a REG_SZ(read_s), REG_DWORD(read_i), or REG_BINARY(read_bin)
    # registry value named name.
    #
    # If the values type does not match, TypeError is raised.
    #
    def read_i(name)
      read(name, REG_DWORD, REG_DWORD_BIG_ENDIAN, REG_QWORD)[1]
    end

    #
    # Read a REG_SZ(read_s), REG_DWORD(read_i), or REG_BINARY(read_bin)
    # registry value named name.
    #
    # If the values type does not match, TypeError is raised.
    #
    def read_bin(name)
      read(name, REG_BINARY)[1]
    end

    #
    # Write data to a registry value named name.
    # When name is nil, write to the `default' value.
    #
    # type is type value. (see Registry::Constants module)
    # Class of data must be same as which #read
    # method returns.
    #
    def write(name, type, data)
      case type
      when REG_SZ, REG_EXPAND_SZ
        data = data.to_s + "\0"
      when REG_MULTI_SZ
        data = data.to_a.join("\0") + "\0\0"
      when REG_BINARY
        data = data.to_s
      when REG_DWORD
        data = API.packdw(data.to_i)
      when REG_DWORD_BIG_ENDIAN
        data = [data.to_i].pack('N')
      when REG_QWORD
        data = API.packqw(data.to_i)
      else
        raise TypeError, "Unsupported type #{type}"
      end
      API.SetValue(@hkey, name, type, data, data.length)
    end

    #
    # Write value to a registry value named name.
    #
    # If wtype is specified, the value type is it.
    # Otherwise, the value type is depend on class of value:
    # :Integer
    #   REG_DWORD
    # :String
    #   REG_SZ
    # :Array
    #   REG_MULTI_SZ
    #
    def []=(name, rtype, value = nil)
      if value
        write name, rtype, value
      else
        case value = rtype
        when Integer
          write name, REG_DWORD, value
        when String
          write name, REG_SZ, value
        when Array
          write name, REG_MULTI_SZ, value
        else
          raise TypeError, "Unexpected type #{value.class}"
        end
      end
      value
    end

    #
    # Write value to a registry value named name.
    #
    # The value type is REG_SZ(write_s), REG_DWORD(write_i), or
    # REG_BINARY(write_bin).
    #
    def write_s(name, value)
      write name, REG_SZ, value.to_s
    end

    #
    # Write value to a registry value named name.
    #
    # The value type is REG_SZ(write_s), REG_DWORD(write_i), or
    # REG_BINARY(write_bin).
    #
    def write_i(name, value)
      write name, REG_DWORD, value.to_i
    end

    #
    # Write value to a registry value named name.
    #
    # The value type is REG_SZ(write_s), REG_DWORD(write_i), or
    # REG_BINARY(write_bin).
    #
    def write_bin(name, value)
      write name, REG_BINARY, value.to_s
    end

    #
    # Delete a registry value named name.
    # We can not delete the `default' value.
    #
    def delete_value(name)
      API.DeleteValue(@hkey, name)
    end
    alias delete delete_value

    #
    # Delete a subkey named name and all its values.
    #
    # If recursive is false, the subkey must not have subkeys.
    # Otherwise, this method deletes all subkeys and values recursively.
    #
    def delete_key(name, recursive = false)
      if recursive
        open(name, KEY_ALL_ACCESS) do |reg|
          reg.keys.each do |key|
            begin
              reg.delete_key(key, true)
            rescue Error
              #
            end
          end
        end
        API.DeleteKey(@hkey, name)
      else
        begin
          API.EnumKey @hkey, 0
        rescue Error
          return API.DeleteKey(@hkey, name)
        end
        raise Error.new(5) ## ERROR_ACCESS_DENIED
      end
    end

    #
    # Write all the attributes into the registry file.
    #
    def flush
      API.FlushKey @hkey
    end

    #
    # Returns key information as Array of:
    # :num_keys
    #   The number of subkeys.
    # :max_key_length
    #   Maximum length of name of subkeys.
    # :num_values
    #   The number of values.
    # :max_value_name_length
    #   Maximum length of name of values.
    # :max_value_length
    #   Maximum length of value of values.
    # :descriptor_length
    #   Length of security descriptor.
    # :wtime
    #   Last write time as FILETIME(64-bit integer)
    #
    # For detail, see RegQueryInfoKey[http://msdn.microsoft.com/library/en-us/sysinfo/base/regqueryinfokey.asp] Win32 API.
    #
    def info
      API.QueryInfoKey(@hkey)
    end

    #
    # Returns an item of key information.
    #
    %w[
      num_keys max_key_length
      num_values max_value_name_length max_value_length
      descriptor_length wtime
    ].each_with_index do |s, i|
      eval <<-__END__
        def #{s}
          info[#{i}]
        end
      __END__
    end
  end
end