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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=8 sts=2 et sw=2 tw=80: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #include "nsCxPusher.h"

 #include "nsIScriptContext.h"

 #include "mozilla/dom/EventTarget.h"

 #include "nsDOMJSUtils.h"

 #include "xpcprivate.h"

 #include "WorkerPrivate.h"

 using mozilla::dom::EventTarget;

 using mozilla::DebugOnly;

 bool

 nsCxPusher::Push(EventTarget *aCurrentTarget)

 {

   MOZ_ASSERT(mPusher.empty());

   NS_ENSURE_TRUE(aCurrentTarget, false);

   nsresult rv;

   nsIScriptContext* scx =

     aCurrentTarget->GetContextForEventHandlers(&rv);

 #ifdef DEBUG_smaug

   NS_ENSURE_SUCCESS(rv, false);

 #else

   if(NS_FAILED(rv)) {

     return false;

   }

 #endif

   if (!scx) {

     // The target may have a special JS context for event handlers.

     JSContext* cx = aCurrentTarget->GetJSContextForEventHandlers();

     if (cx) {

       mPusher.construct(cx);

     }

     // Nothing to do here, I guess.  Have to return true so that event firing

     // will still work correctly even if there is no associated JSContext

     return true;

   }

   mPusher.construct(scx->GetNativeContext());

   return true;

 }

 bool

 nsCxPusher::RePush(EventTarget *aCurrentTarget)

 {

   if (mPusher.empty()) {

     return Push(aCurrentTarget);

   }

   if (aCurrentTarget) {

     nsresult rv;

     nsIScriptContext* scx =

       aCurrentTarget->GetContextForEventHandlers(&rv);

     if (NS_FAILED(rv)) {

       mPusher.destroy();

       return false;

     }

     // If we have the same script context and native context is still

     // alive, no need to Pop/Push.

     if (scx && scx == mPusher.ref().GetScriptContext() &&

         scx->GetNativeContext()) {

       return true;

     }

   }

   mPusher.destroy();

   return Push(aCurrentTarget);

 }

 void

 nsCxPusher::Push(JSContext *cx)

 {

   mPusher.construct(cx);

 }

 void

 nsCxPusher::PushNull()

 {

   // Note: The Maybe<> template magic seems to need the static_cast below to

   // work right on some older compilers.

   mPusher.construct(static_cast<JSContext*>(nullptr), /* aAllowNull = */ true);

 }

 void

 nsCxPusher::Pop()

 {

   if (!mPusher.empty())

     mPusher.destroy();

 }

 namespace mozilla {

 AutoCxPusher::AutoCxPusher(JSContext* cx, bool allowNull)

 {

   MOZ_ASSERT_IF(!allowNull, cx);

   // Hold a strong ref to the nsIScriptContext, if any. This ensures that we

   // only destroy the mContext of an nsJSContext when it is not on the cx stack

   // (and therefore not in use). See nsJSContext::DestroyJSContext().

   if (cx)

     mScx = GetScriptContextFromJSContext(cx);

   XPCJSContextStack *stack = XPCJSRuntime::Get()->GetJSContextStack();

   if (!stack->Push(cx)) {

     MOZ_CRASH();

   }

   mStackDepthAfterPush = stack->Count();

 #ifdef DEBUG

   mPushedContext = cx;

   mCompartmentDepthOnEntry = cx ? js::GetEnterCompartmentDepth(cx) : 0;

 #endif

   // Enter a request and a compartment for the duration that the cx is on the

   // stack if non-null.

   if (cx) {

     mAutoRequest.construct(cx);

     // DOM JSContexts don't store their default compartment object on the cx.

     JSObject *compartmentObject = mScx ? mScx->GetWindowProxy()

                                        : js::DefaultObjectForContextOrNull(cx);

     if (compartmentObject)

       mAutoCompartment.construct(cx, compartmentObject);

   }

 }

 AutoCxPusher::~AutoCxPusher()

 {

   // GC when we pop a script entry point. This is a useful heuristic that helps

   // us out on certain (flawed) benchmarks like sunspider, because it lets us

   // avoid GCing during the timing loop.

   //

   // NB: We need to take care to only do this if we're in a compartment,

   // otherwise JS_MaybeGC will segfault.

   if (mScx && !mAutoCompartment.empty())

     JS_MaybeGC(nsXPConnect::XPConnect()->GetCurrentJSContext());

   // Leave the compartment and request before popping.

   mAutoCompartment.destroyIfConstructed();

   mAutoRequest.destroyIfConstructed();

   // When we push a context, we may save the frame chain and pretend like we

   // haven't entered any compartment. This gets restored on Pop(), but we can

   // run into trouble if a Push/Pop are interleaved with a

   // JSAutoEnterCompartment. Make sure the compartment depth right before we

   // pop is the same as it was right after we pushed.

   MOZ_ASSERT_IF(mPushedContext, mCompartmentDepthOnEntry ==

                                 js::GetEnterCompartmentDepth(mPushedContext));

   DebugOnly<JSContext*> stackTop;

   MOZ_ASSERT(mPushedContext == nsXPConnect::XPConnect()->GetCurrentJSContext());

   XPCJSRuntime::Get()->GetJSContextStack()->Pop();

   mScx = nullptr;

 }

 bool

 AutoCxPusher::IsStackTop()

 {

   uint32_t currentDepth = XPCJSRuntime::Get()->GetJSContextStack()->Count();

   MOZ_ASSERT(currentDepth >= mStackDepthAfterPush);

   return currentDepth == mStackDepthAfterPush;

 }

 AutoJSContext::AutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)

   : mCx(nullptr)

 {

   Init(false MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT);

 }

 AutoJSContext::AutoJSContext(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)

   : mCx(nullptr)

 {

   Init(aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT);

 }

 void

 AutoJSContext::Init(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)

 {

   JS::AutoAssertNoGC nogc;

   MOZ_ASSERT(!mCx, "mCx should not be initialized!");

   MOZ_GUARD_OBJECT_NOTIFIER_INIT;

   nsXPConnect *xpc = nsXPConnect::XPConnect();

   if (!aSafe) {

     mCx = xpc->GetCurrentJSContext();

   }

   if (!mCx) {

     mCx = xpc->GetSafeJSContext();

     mPusher.construct(mCx);

   }

 }

 AutoJSContext::operator JSContext*() const

 {

   return mCx;

 }

 ThreadsafeAutoJSContext::ThreadsafeAutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)

 {

   MOZ_GUARD_OBJECT_NOTIFIER_INIT;

   if (NS_IsMainThread()) {

     mCx = nullptr;

     mAutoJSContext.construct();

   } else {

     mCx = mozilla::dom::workers::GetCurrentThreadJSContext();

     mRequest.construct(mCx);

   }

 }

 ThreadsafeAutoJSContext::operator JSContext*() const

 {

   if (mCx) {

     return mCx;

   } else {

     return mAutoJSContext.ref();

   }

 }

 AutoSafeJSContext::AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)

   : AutoJSContext(true MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)

   , mAc(mCx, XPCJSRuntime::Get()->GetJSContextStack()->GetSafeJSContextGlobal())

 {

 }

 ThreadsafeAutoSafeJSContext::ThreadsafeAutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)

 {

   MOZ_GUARD_OBJECT_NOTIFIER_INIT;

   if (NS_IsMainThread()) {

     mCx = nullptr;

     mAutoSafeJSContext.construct();

   } else {

     mCx = mozilla::dom::workers::GetCurrentThreadJSContext();

     mRequest.construct(mCx);

   }

 }

 ThreadsafeAutoSafeJSContext::operator JSContext*() const

 {

   if (mCx) {

     return mCx;

   } else {

     return mAutoSafeJSContext.ref();

   }

 }

 AutoPushJSContext::AutoPushJSContext(JSContext *aCx) : mCx(aCx)

 {

   if (mCx && mCx != nsXPConnect::XPConnect()->GetCurrentJSContext()) {

     mPusher.construct(mCx);

   }

 }

 } // namespace mozilla