includes/StubObject.php

   1 <?php
   2 /**
   3  * Delayed loading of global objects.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * Class to implement stub globals, which are globals that delay loading the
  25  * their associated module code by deferring initialisation until the first
  26  * method call.
  27  *
  28  * Note on reference parameters:
  29  *
  30  * If the called method takes any parameters by reference, the __call magic
  31  * here won't work correctly. The solution is to unstub the object before
  32  * calling the method.
  33  *
  34  * Note on unstub loops:
  35  *
  36  * Unstub loops (infinite recursion) sometimes occur when a constructor calls
  37  * another function, and the other function calls some method of the stub. The
  38  * best way to avoid this is to make constructors as lightweight as possible,
  39  * deferring any initialisation which depends on other modules. As a last
  40  * resort, you can use StubObject::isRealObject() to break the loop, but as a
  41  * general rule, the stub object mechanism should be transparent, and code
  42  * which refers to it should be kept to a minimum.
  43  */
  44 class StubObject {
  45         var $mGlobal, $mClass, $mParams;
  46
  47         /**
  48          * Constructor.
  49          *
  50          * @param string $global Name of the global variable.
  51          * @param string $class Name of the class of the real object.
  52          * @param array $params Parameters to pass to constructor of the real object.
  53          */
  54         function __construct( $global = null, $class = null, $params = array() ) {
  55                 $this->mGlobal = $global;
  56                 $this->mClass = $class;
  57                 $this->mParams = $params;
  58         }
  59
  60         /**
  61          * Returns a bool value whenever $obj is a stub object. Can be used to break
  62          * a infinite loop when unstubbing an object.
  63          *
  64          * @param object $obj Object to check.
  65          * @return bool True if $obj is not an instance of StubObject class.
  66          */
  67         static function isRealObject( $obj ) {
  68                 return is_object( $obj ) && !$obj instanceof StubObject;
  69         }
  70
  71         /**
  72          * Unstubs an object, if it is a stub object. Can be used to break a
  73          * infinite loop when unstubbing an object or to avoid reference parameter
  74          * breakage.
  75          *
  76          * @param object $obj Object to check.
  77          * @return void
  78          */
  79         static function unstub( $obj ) {
  80                 if ( $obj instanceof StubObject ) {
  81                         $obj->_unstub( 'unstub', 3 );
  82                 }
  83         }
  84
  85         /**
  86          * Function called if any function exists with that name in this object.
  87          * It is used to unstub the object. Only used internally, PHP will call
  88          * self::__call() function and that function will call this function.
  89          * This function will also call the function with the same name in the real
  90          * object.
  91          *
  92          * @param string $name Name of the function called
  93          * @param array $args Arguments
  94          * @return mixed
  95          */
  96         function _call( $name, $args ) {
  97                 $this->_unstub( $name, 5 );
  98                 return call_user_func_array( array( $GLOBALS[$this->mGlobal], $name ), $args );
  99         }
 100
 101         /**
 102          * Create a new object to replace this stub object.
 103          * @return object
 104          */
 105         function _newObject() {
 106                 return MWFunction::newObj( $this->mClass, $this->mParams );
 107         }
 108
 109         /**
 110          * Function called by PHP if no function with that name exists in this
 111          * object.
 112          *
 113          * @param string $name Name of the function called
 114          * @param array $args Arguments
 115          * @return mixed
 116          */
 117         function __call( $name, $args ) {
 118                 return $this->_call( $name, $args );
 119         }
 120
 121         /**
 122          * This function creates a new object of the real class and replace it in
 123          * the global variable.
 124          * This is public, for the convenience of external callers wishing to access
 125          * properties, e.g. eval.php
 126          *
 127          * @param string $name Name of the method called in this object.
 128          * @param int $level Level to go in the stack trace to get the function
 129          *   who called this function.
 130          * @throws MWException
 131          */
 132         function _unstub( $name = '_unstub', $level = 2 ) {
 133                 static $recursionLevel = 0;
 134
 135                 if ( !$GLOBALS[$this->mGlobal] instanceof StubObject ) {
 136                         return $GLOBALS[$this->mGlobal]; // already unstubbed.
 137                 }
 138
 139                 if ( get_class( $GLOBALS[$this->mGlobal] ) != $this->mClass ) {
 140                         $fname = __METHOD__ . '-' . $this->mGlobal;
 141                         wfProfileIn( $fname );
 142                         $caller = wfGetCaller( $level );
 143                         if ( ++$recursionLevel > 2 ) {
 144                                 wfProfileOut( $fname );
 145                                 throw new MWException( "Unstub loop detected on call of \${$this->mGlobal}->$name from $caller\n" );
 146                         }
 147                         wfDebug( "Unstubbing \${$this->mGlobal} on call of \${$this->mGlobal}::$name from $caller\n" );
 148                         $GLOBALS[$this->mGlobal] = $this->_newObject();
 149                         --$recursionLevel;
 150                         wfProfileOut( $fname );
 151                 }
 152         }
 153 }
 154
 155 /**
 156  * Stub object for the content language of this wiki. This object have to be in
 157  * $wgContLang global.
 158  *
 159  * @deprecated since 1.18
 160  */
 161 class StubContLang extends StubObject {
 162
 163         function __construct() {
 164                 wfDeprecated( __CLASS__, '1.18' );
 165                 parent::__construct( 'wgContLang' );
 166         }
 167
 168         function __call( $name, $args ) {
 169                 return $this->_call( $name, $args );
 170         }
 171
 172         /**
 173          * @return Language
 174          */
 175         function _newObject() {
 176                 global $wgLanguageCode;
 177                 $obj = Language::factory( $wgLanguageCode );
 178                 $obj->initEncoding();
 179                 $obj->initContLang();
 180                 return $obj;
 181         }
 182 }
 183
 184 /**
 185  * Stub object for the user language. It depends of the user preferences and
 186  * "uselang" parameter that can be passed to index.php. This object have to be
 187  * in $wgLang global.
 188  */
 189 class StubUserLang extends StubObject {
 190
 191         function __construct() {
 192                 parent::__construct( 'wgLang' );
 193         }
 194
 195         function __call( $name, $args ) {
 196                 return $this->_call( $name, $args );
 197         }
 198
 199         /**
 200          * @return Language
 201          */
 202         function _newObject() {
 203                 return RequestContext::getMain()->getLanguage();
 204         }
 205 }