Line data    Source code

       1             : /* Copyright (C) 2021 Wildfire Games.
       2             :  * This file is part of 0 A.D.
       3             :  *
       4             :  * 0 A.D. is free software: you can redistribute it and/or modify
       5             :  * it under the terms of the GNU General Public License as published by
       6             :  * the Free Software Foundation, either version 2 of the License, or
       7             :  * (at your option) any later version.
       8             :  *
       9             :  * 0 A.D. is distributed in the hope that it will be useful,
      10             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12             :  * GNU General Public License for more details.
      13             :  *
      14             :  * You should have received a copy of the GNU General Public License
      15             :  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
      16             :  */
      17             : 
      18             : #ifndef INCLUDED_SCRIPTREQUEST
      19             : #define INCLUDED_SCRIPTREQUEST
      20             : 
      21             : #include "scriptinterface/ScriptForward.h"
      22             : 
      23             : // Ignore warnings in SM headers.
      24             : #if GCC_VERSION || CLANG_VERSION
      25             : # pragma GCC diagnostic push
      26             : # pragma GCC diagnostic ignored "-Wunused-parameter"
      27             : # pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
      28             : #elif MSC_VERSION
      29             : # pragma warning(push, 1)
      30             : #endif
      31             : 
      32             : #include "js/RootingAPI.h"
      33             : 
      34             : #if GCC_VERSION || CLANG_VERSION
      35             : # pragma GCC diagnostic pop
      36             : #elif MSC_VERSION
      37             : # pragma warning(pop)
      38             : #endif
      39             : 
      40             : #include <memory>
      41             : 
      42             : class ScriptInterface;
      43             : 
      44             : /**
      45             :  * Spidermonkey maintains some 'local' state via the JSContext* object.
      46             :  * This object is an argument to most JSAPI functions.
      47             :  * Furthermore, this state is Realm (~ global) dependent. For many reasons, including GC safety,
      48             :  * The JSContext* Realm must be set up correctly when accessing it.
      49             :  * 'Entering' and 'Leaving' realms must be done in a LIFO manner.
      50             :  * SM recommends using JSAutoRealm, which provides an RAII option.
      51             :  *
      52             :  * ScriptRequest combines both of the above in a single convenient package,
      53             :  * providing safe access to the JSContext*, the global object, and ensuring that the proper realm has been entered.
      54             :  * Most scriptinterface/ functions will take a ScriptRequest, to ensure proper rooting. You may sometimes
      55             :  * have to create one from a ScriptInterface.
      56             :  *
      57             :  * Be particularly careful when manipulating several script interfaces.
      58             :  */
      59             : class ScriptRequest
      60             : {
      61             :     ScriptRequest() = delete;
      62             :     ScriptRequest(const ScriptRequest& rq) = delete;
      63             :     ScriptRequest& operator=(const ScriptRequest& rq) = delete;
      64             : public:
      65             :     /**
      66             :      * NB: the definitions are in scriptinterface.cpp, because these access members of the PImpled
      67             :      * implementation of ScriptInterface, and that seemed more convenient.
      68             :      */
      69             :     ScriptRequest(const ScriptInterface& scriptInterface);
      70       30504 :     ScriptRequest(const ScriptInterface* scriptInterface) : ScriptRequest(*scriptInterface) {}
      71          27 :     ScriptRequest(std::shared_ptr<ScriptInterface> scriptInterface) : ScriptRequest(*scriptInterface) {}
      72             :     ~ScriptRequest();
      73             : 
      74             :     /**
      75             :      * Create a script request from a JSContext.
      76             :      * This can be used to get the script interface in a JSNative function.
      77             :      * In general, you shouldn't have to rely on this otherwise.
      78             :      */
      79             :     ScriptRequest(JSContext* cx);
      80             : 
      81             :     /**
      82             :      * Return the scriptInterface active when creating this ScriptRequest.
      83             :      * Note that this is multi-request safe: even if another ScriptRequest is created,
      84             :      * it will point to the original scriptInterface, and thus can be used to re-enter the realm.
      85             :      */
      86             :     const ScriptInterface& GetScriptInterface() const;
      87             : 
      88             :     JS::Value globalValue() const;
      89             : 
      90             :     // Note that JSContext actually changes behind the scenes when creating another ScriptRequest for another realm,
      91             :     // so be _very_ careful when juggling between different realms.
      92             :     JSContext* cx;
      93             :     JS::HandleObject glob;
      94             :     JS::HandleObject nativeScope;
      95             : private:
      96             :     const ScriptInterface& m_ScriptInterface;
      97             :     JS::Realm* m_FormerRealm;
      98             : };
      99             : 
     100             : 
     101             : #endif // INCLUDED_SCRIPTREQUEST