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      1 /*
      2  * Copyright (C) 2009 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef V8IsolatedContext_h
     32 #define V8IsolatedContext_h
     33 
     34 #include "IsolatedWorld.h"
     35 #include "ScriptSourceCode.h" // for WebCore::ScriptSourceCode
     36 #include "V8DOMWindow.h"
     37 #include "V8Proxy.h"
     38 #include "V8Utilities.h"
     39 #include <v8.h>
     40 
     41 namespace WebCore {
     42 
     43 class V8Proxy;
     44 
     45 // V8IsolatedContext
     46 //
     47 // V8IsolatedContext represents a isolated execution environment for
     48 // JavaScript.  Each isolated world executes in parallel with the main
     49 // JavaScript world.  An isolated world has access to the same DOM data
     50 // structures as the main world but none of the JavaScript pointers.
     51 //
     52 // It is an error to ever share a JavaScript pointer between two isolated
     53 // worlds or between an isolated world and the main world.  Because
     54 // isolated worlds have access to the DOM, they need their own DOM wrappers
     55 // to avoid having pointers to the main world's DOM wrappers (which are
     56 // JavaScript objects).
     57 class V8IsolatedContext {
     58 public:
     59     // Creates an isolated world. To destroy it, call destroy().
     60     // This will delete the isolated world when the context it owns is GC'd.
     61     V8IsolatedContext(V8Proxy* proxy, int extensionGroup);
     62     ~V8IsolatedContext();
     63 
     64     // Call this to destroy the isolated world. It will be deleted sometime
     65     // after this call, once all script references to the world's context
     66     // have been dropped.
     67     void destroy();
     68 
     69     // Returns the isolated world associated with
     70     // v8::Context::GetEntered().  Because worlds are isolated, the entire
     71     // JavaScript call stack should be from the same isolated world.
     72     // Returns 0 if the entered context is from the main world.
     73     //
     74     // FIXME: Consider edge cases with DOM mutation events that might
     75     // violate this invariant.
     76     //
     77     static V8IsolatedContext* getEntered()
     78     {
     79         // This is a temporary performance optimization.   Essentially,
     80         // GetHiddenValue is too slow for this code path.  We need to get the
     81         // V8 team to add a real property to v8::Context for isolated worlds.
     82         // Until then, we optimize the common case of not having any isolated
     83         // worlds at all.
     84         if (!IsolatedWorld::count())
     85             return 0;
     86         if (!v8::Context::InContext())
     87             return 0;
     88         return reinterpret_cast<V8IsolatedContext*>(getGlobalObject(v8::Context::GetEntered())->GetPointerFromInternalField(V8DOMWindow::enteredIsolatedWorldIndex));
     89     }
     90 
     91     v8::Handle<v8::Context> context() { return m_context->get(); }
     92     PassRefPtr<SharedPersistent<v8::Context> > sharedContext() { return m_context; }
     93 
     94     IsolatedWorld* world() const { return m_world.get(); }
     95 
     96 private:
     97     static v8::Handle<v8::Object> getGlobalObject(v8::Handle<v8::Context> context)
     98     {
     99         return v8::Handle<v8::Object>::Cast(context->Global()->GetPrototype());
    100     }
    101 
    102     // Called by the garbage collector when our JavaScript context is about
    103     // to be destroyed.
    104     static void contextWeakReferenceCallback(v8::Persistent<v8::Value> object, void* isolatedContext);
    105 
    106     // The underlying v8::Context. This object is keep on the heap as
    107     // long as |m_context| has not been garbage collected.
    108     RefPtr<SharedPersistent<v8::Context> > m_context;
    109 
    110     RefPtr<IsolatedWorld> m_world;
    111 };
    112 
    113 } // namespace WebCore
    114 
    115 #endif // V8IsolatedContext_h
    116