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 unstub loops:
  29  *
  30  * Unstub loops (infinite recursion) sometimes occur when a constructor calls
  31  * another function, and the other function calls some method of the stub. The
  32  * best way to avoid this is to make constructors as lightweight as possible,
  33  * deferring any initialisation which depends on other modules. As a last
  34  * resort, you can use StubObject::isRealObject() to break the loop, but as a
  35  * general rule, the stub object mechanism should be transparent, and code
  36  * which refers to it should be kept to a minimum.
  37  */
  38 class StubObject {
  39         var $mGlobal, $mClass, $mParams;
  40
  41         /**
  42          * Constructor.
  43          *
  44          * @param string $global name of the global variable.
  45          * @param string $class name of the class of the real object.
  46          * @param array $params parameters to pass to constructor of the real
  47          *               object.
  48          */
  49         function __construct( $global = null, $class = null, $params = array() ) {
  50                 $this->mGlobal = $global;
  51                 $this->mClass = $class;
  52                 $this->mParams = $params;
  53         }
  54
  55         /**
  56          * Returns a bool value whenever $obj is a stub object. Can be used to break
  57          * a infinite loop when unstubbing an object.
  58          *
  59          * @param $obj Object to check.
  60          * @return Boolean: true if $obj is not an instance of StubObject class.
  61          */
  62         static function isRealObject( $obj ) {
  63                 return is_object( $obj ) && !$obj instanceof StubObject;
  64         }
  65
  66         /**
  67          * Function called if any function exists with that name in this object.
  68          * It is used to unstub the object. Only used internally, PHP will call
  69          * self::__call() function and that function will call this function.
  70          * This function will also call the function with the same name in the real
  71          * object.
  72          *
  73          * @param string $name name of the function called
  74          * @param array $args arguments
  75          * @return mixed
  76          */
  77         function _call( $name, $args ) {
  78                 $this->_unstub( $name, 5 );
  79                 return call_user_func_array( array( $GLOBALS[$this->mGlobal], $name ), $args );
  80         }
  81
  82         /**
  83          * Create a new object to replace this stub object.
  84          * @return object
  85          */
  86         function _newObject() {
  87                 return MWFunction::newObj( $this->mClass, $this->mParams );
  88         }
  89
  90         /**
  91          * Function called by PHP if no function with that name exists in this
  92          * object.
  93          *
  94          * @param string $name name of the function called
  95          * @param array $args arguments
  96          * @return mixed
  97          */
  98         function __call( $name, $args ) {
  99                 return $this->_call( $name, $args );
 100         }
 101
 102         /**
 103          * This function creates a new object of the real class and replace it in
 104          * the global variable.
 105          * This is public, for the convenience of external callers wishing to access
 106          * properties, e.g. eval.php
 107          *
 108          * @param string $name name of the method called in this object.
 109          * @param $level Integer: level to go in the stack trace to get the function
 110          *               who called this function.
 111          * @throws MWException
 112          */
 113         function _unstub( $name = '_unstub', $level = 2 ) {
 114                 static $recursionLevel = 0;
 115
 116                 if ( !$GLOBALS[$this->mGlobal] instanceof StubObject ) {
 117                         return $GLOBALS[$this->mGlobal]; // already unstubbed.
 118                 }
 119
 120                 if ( get_class( $GLOBALS[$this->mGlobal] ) != $this->mClass ) {
 121                         $fname = __METHOD__ . '-' . $this->mGlobal;
 122                         wfProfileIn( $fname );
 123                         $caller = wfGetCaller( $level );
 124                         if ( ++$recursionLevel > 2 ) {
 125                                 wfProfileOut( $fname );
 126                                 throw new MWException( "Unstub loop detected on call of \${$this->mGlobal}->$name from $caller\n" );
 127                         }
 128                         wfDebug( "Unstubbing \${$this->mGlobal} on call of \${$this->mGlobal}::$name from $caller\n" );
 129                         $GLOBALS[$this->mGlobal] = $this->_newObject();
 130                         --$recursionLevel;
 131                         wfProfileOut( $fname );
 132                 }
 133         }
 134 }
 135
 136 /**
 137  * Stub object for the content language of this wiki. This object have to be in
 138  * $wgContLang global.
 139  *
 140  * @deprecated since 1.18
 141  */
 142 class StubContLang extends StubObject {
 143
 144         function __construct() {
 145                 wfDeprecated( __CLASS__, '1.18' );
 146                 parent::__construct( 'wgContLang' );
 147         }
 148
 149         function __call( $name, $args ) {
 150                 return $this->_call( $name, $args );
 151         }
 152
 153         /**
 154          * @return Language
 155          */
 156         function _newObject() {
 157                 global $wgLanguageCode;
 158                 $obj = Language::factory( $wgLanguageCode );
 159                 $obj->initEncoding();
 160                 $obj->initContLang();
 161                 return $obj;
 162         }
 163 }
 164
 165 /**
 166  * Stub object for the user language. It depends of the user preferences and
 167  * "uselang" parameter that can be passed to index.php. This object have to be
 168  * in $wgLang global.
 169  */
 170 class StubUserLang extends StubObject {
 171
 172         function __construct() {
 173                 parent::__construct( 'wgLang' );
 174         }
 175
 176         function __call( $name, $args ) {
 177                 return $this->_call( $name, $args );
 178         }
 179
 180         /**
 181          * @return Language
 182          */
 183         function _newObject() {
 184                 return RequestContext::getMain()->getLanguage();
 185         }
 186 }