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
  53          *               object.
  54          */
  55         function __construct( $global = null, $class = null, $params = array() ) {
  56                 $this->mGlobal = $global;
  57                 $this->mClass = $class;
  58                 $this->mParams = $params;
  59         }
  60
  61         /**
  62          * Returns a bool value whenever $obj is a stub object. Can be used to break
  63          * a infinite loop when unstubbing an object.
  64          *
  65          * @param $obj Object to check.
  66          * @return Boolean: true if $obj is not an instance of StubObject class.
  67          */
  68         static function isRealObject( $obj ) {
  69                 return is_object( $obj ) && !$obj instanceof StubObject;
  70         }
  71
  72         /**
  73          * Unstubs an object, if it is a stub object. Can be used to break a
  74          * infinite loop when unstubbing an object or to avoid reference parameter
  75          * breakage.
  76          *
  77          * @param $obj Object to check.
  78          * @return void
  79          */
  80         static function unstub( $obj ) {
  81                 if ( $obj instanceof StubObject ) {
  82                         $obj->_unstub( 'unstub', 3 );
  83                 }
  84         }
  85
  86         /**
  87          * Function called if any function exists with that name in this object.
  88          * It is used to unstub the object. Only used internally, PHP will call
  89          * self::__call() function and that function will call this function.
  90          * This function will also call the function with the same name in the real
  91          * object.
  92          *
  93          * @param string $name name of the function called
  94          * @param array $args arguments
  95          * @return mixed
  96          */
  97         function _call( $name, $args ) {
  98                 $this->_unstub( $name, 5 );
  99                 return call_user_func_array( array( $GLOBALS[$this->mGlobal], $name ), $args );
 100         }
 101
 102         /**
 103          * Create a new object to replace this stub object.
 104          * @return object
 105          */
 106         function _newObject() {
 107                 return MWFunction::newObj( $this->mClass, $this->mParams );
 108         }
 109
 110         /**
 111          * Function called by PHP if no function with that name exists in this
 112          * object.
 113          *
 114          * @param string $name name of the function called
 115          * @param array $args arguments
 116          * @return mixed
 117          */
 118         function __call( $name, $args ) {
 119                 return $this->_call( $name, $args );
 120         }
 121
 122         /**
 123          * This function creates a new object of the real class and replace it in
 124          * the global variable.
 125          * This is public, for the convenience of external callers wishing to access
 126          * properties, e.g. eval.php
 127          *
 128          * @param string $name name of the method called in this object.
 129          * @param $level Integer: level to go in the stack trace to get the function
 130          *               who called this function.
 131          * @throws MWException
 132          */
 133         function _unstub( $name = '_unstub', $level = 2 ) {
 134                 static $recursionLevel = 0;
 135
 136                 if ( !$GLOBALS[$this->mGlobal] instanceof StubObject ) {
 137                         return $GLOBALS[$this->mGlobal]; // already unstubbed.
 138                 }
 139
 140                 if ( get_class( $GLOBALS[$this->mGlobal] ) != $this->mClass ) {
 141                         $fname = __METHOD__ . '-' . $this->mGlobal;
 142                         wfProfileIn( $fname );
 143                         $caller = wfGetCaller( $level );
 144                         if ( ++$recursionLevel > 2 ) {
 145                                 wfProfileOut( $fname );
 146                                 throw new MWException( "Unstub loop detected on call of \${$this->mGlobal}->$name from $caller\n" );
 147                         }
 148                         wfDebug( "Unstubbing \${$this->mGlobal} on call of \${$this->mGlobal}::$name from $caller\n" );
 149                         $GLOBALS[$this->mGlobal] = $this->_newObject();
 150                         --$recursionLevel;
 151                         wfProfileOut( $fname );
 152                 }
 153         }
 154 }
 155
 156 /**
 157  * Stub object for the content language of this wiki. This object have to be in
 158  * $wgContLang global.
 159  *
 160  * @deprecated since 1.18
 161  */
 162 class StubContLang extends StubObject {
 163
 164         function __construct() {
 165                 wfDeprecated( __CLASS__, '1.18' );
 166                 parent::__construct( 'wgContLang' );
 167         }
 168
 169         function __call( $name, $args ) {
 170                 return $this->_call( $name, $args );
 171         }
 172
 173         /**
 174          * @return Language
 175          */
 176         function _newObject() {
 177                 global $wgLanguageCode;
 178                 $obj = Language::factory( $wgLanguageCode );
 179                 $obj->initEncoding();
 180                 $obj->initContLang();
 181                 return $obj;
 182         }
 183 }
 184
 185 /**
 186  * Stub object for the user language. It depends of the user preferences and
 187  * "uselang" parameter that can be passed to index.php. This object have to be
 188  * in $wgLang global.
 189  */
 190 class StubUserLang extends StubObject {
 191
 192         function __construct() {
 193                 parent::__construct( 'wgLang' );
 194         }
 195
 196         function __call( $name, $args ) {
 197                 return $this->_call( $name, $args );
 198         }
 199
 200         /**
 201          * @return Language
 202          */
 203         function _newObject() {
 204                 return RequestContext::getMain()->getLanguage();
 205         }
 206 }