C++ XPCJSContextStack类代码示例

danger::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.emplace(cx);
  }
}

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);
  }
}

void
xpc_qsAssertContextOK(JSContext *cx)
{
    XPCJSContextStack* stack = XPCJSRuntime::Get()->GetJSContextStack();

    JSContext *topJSContext = stack->Peek();

    // This is what we're actually trying to assert here.
    MOZ_ASSERT(cx == topJSContext, "wrong context on XPCJSContextStack!");
}

// static
void
XPCLazyCallContext::AssertContextIsTopOfStack(JSContext* cx)
{
    XPCPerThreadData* tls = XPCPerThreadData::GetData(cx);
    XPCJSContextStack* stack = tls->GetJSContextStack();

    JSContext* topJSContext;
    nsresult rv = stack->Peek(&topJSContext);
    NS_ASSERTION(NS_SUCCEEDED(rv), "XPCJSContextStack::Peek failed");

    NS_ASSERTION(cx == topJSContext, "wrong context on XPCJSContextStack!");
}

void
xpc_qsAssertContextOK(JSContext *cx)
{
    XPCPerThreadData *thread = XPCPerThreadData::GetData(cx);
    XPCJSContextStack* stack = thread->GetJSContextStack();

    JSContext* topJSContext = nsnull;
    nsresult rv = stack->Peek(&topJSContext);
    NS_ASSERTION(NS_SUCCEEDED(rv), "XPCJSContextStack::Peek failed");

    // This is what we're actually trying to assert here.
    NS_ASSERTION(cx == topJSContext, "wrong context on XPCJSContextStack!");

    NS_ASSERTION(XPCPerThreadData::IsMainThread(cx),
                 "XPConnect quick stub called on non-main thread");
}

AutoCxPusher::AutoCxPusher(JSContext* cx, bool allowNull) : mScriptIsRunning(false)
{
  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);

  // NB: The GetDynamicScriptContext is historical and might not be sane.
  XPCJSContextStack *stack = XPCJSRuntime::Get()->GetJSContextStack();
  if (cx && nsJSUtils::GetDynamicScriptContext(cx) && stack->HasJSContext(cx))
  {
    // If the context is on the stack, that means that a script
    // is running at the moment in the context.
    mScriptIsRunning = true;
  }

  if (!stack->Push(cx)) {
    MOZ_CRASH();
  }

#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.
  //
  // NB: We call UnmarkGrayContext so that this can obsolete the need for the
  // old XPCAutoRequest as well.
  if (cx) {
    mAutoRequest.construct(cx);
    if (js::DefaultObjectForContextOrNull(cx))
      mAutoCompartment.construct(cx, js::DefaultObjectForContextOrNull(cx));
    xpc_UnmarkGrayContext(cx);
  }
}

void
XPCCallContext::Init(XPCContext::LangType callerLanguage,
                     JSBool callBeginRequest,
                     JSObject* obj,
                     JSObject* funobj,
                     WrapperInitOptions wrapperInitOptions,
                     jsid name,
                     uintN argc,
                     jsval *argv,
                     jsval *rval)
{
    if (!mXPC)
        return;

    mThreadData = XPCPerThreadData::GetData(mJSContext);

    if (!mThreadData)
        return;

    XPCJSContextStack* stack = mThreadData->GetJSContextStack();
    JSContext* topJSContext;

    if (!stack || NS_FAILED(stack->Peek(&topJSContext))) {
        // If we don't have a stack we're probably in shutdown.
        NS_ASSERTION(!stack, "Bad, Peek failed!");
        mJSContext = nsnull;
        return;
    }

    if (!mJSContext) {
        // This is slightly questionable. If called without an explicit
        // JSContext (generally a call to a wrappedJS) we will use the JSContext
        // on the top of the JSContext stack - if there is one - *before*
        // falling back on the safe JSContext.
        // This is good AND bad because it makes calls from JS -> native -> JS
        // have JS stack 'continuity' for purposes of stack traces etc.
        // Note: this *is* what the pre-XPCCallContext xpconnect did too.

        if (topJSContext)
            mJSContext = topJSContext;
        else if (NS_FAILED(stack->GetSafeJSContext(&mJSContext)) || !mJSContext)
            return;
    }

    if (topJSContext != mJSContext) {
        if (NS_FAILED(stack->Push(mJSContext))) {
            NS_ERROR("bad!");
            return;
        }
        mContextPopRequired = true;
    }

    // Get into the request as early as we can to avoid problems with scanning
    // callcontexts on other threads from within the gc callbacks.

    NS_ASSERTION(!callBeginRequest || mCallerLanguage == NATIVE_CALLER,
                 "Don't call JS_BeginRequest unless the caller is native.");
    if (callBeginRequest)
        JS_BeginRequest(mJSContext);

    mXPCContext = XPCContext::GetXPCContext(mJSContext);
    mPrevCallerLanguage = mXPCContext->SetCallingLangType(mCallerLanguage);

    // hook into call context chain for our thread
    mPrevCallContext = mThreadData->SetCallContext(this);

    // We only need to addref xpconnect once so only do it if this is the first
    // context in the chain.
    if (!mPrevCallContext)
        NS_ADDREF(mXPC);

    mState = HAVE_CONTEXT;

    if (!obj)
        return;

    mScopeForNewJSObjects = obj;

    mState = HAVE_SCOPE;

    mMethodIndex = 0xDEAD;

    mState = HAVE_OBJECT;

    mTearOff = nsnull;
    if (wrapperInitOptions == INIT_SHOULD_LOOKUP_WRAPPER) {
        mWrapper = XPCWrappedNative::GetWrappedNativeOfJSObject(mJSContext, obj,
                                                                funobj,
                                                                &mFlattenedJSObject,
                                                                &mTearOff);
        if (mWrapper) {
            DEBUG_CheckWrapperThreadSafety(mWrapper);

            mFlattenedJSObject = mWrapper->GetFlatJSObject();

            if (mTearOff)
                mScriptableInfo = nsnull;
            else
                mScriptableInfo = mWrapper->GetScriptableInfo();
        } else {
//.........这里部分代码省略.........

XPCCallContext::XPCCallContext(XPCContext::LangType callerLanguage,
                               JSContext* cx    /* = nsnull  */,
                               JSObject* obj    /* = nsnull  */,
                               JSObject* funobj /* = nsnull  */,
                               jsval name       /* = 0       */,
                               uintN argc       /* = NO_ARGS */,
                               jsval *argv      /* = nsnull  */,
                               jsval *rval      /* = nsnull  */)
    :   mState(INIT_FAILED),
        mXPC(nsXPConnect::GetXPConnect()),
        mThreadData(nsnull),
        mXPCContext(nsnull),
        mJSContext(cx),
        mContextPopRequired(JS_FALSE),
        mDestroyJSContextInDestructor(JS_FALSE),
        mCallerLanguage(callerLanguage),
        mCallee(nsnull)
{
    // Mark our internal string wrappers as not used. Make sure we do
    // this before any early returns, as the destructor will assert
    // based on this.
    StringWrapperEntry *se =
        reinterpret_cast<StringWrapperEntry*>(&mStringWrapperData);

    PRUint32 i;
    for(i = 0; i < XPCCCX_STRING_CACHE_SIZE; ++i)
    {
        se[i].mInUse = PR_FALSE;
    }

    if(!mXPC)
        return;

    mThreadData = XPCPerThreadData::GetData(mJSContext);

    if(!mThreadData)
        return;

    XPCJSContextStack* stack = mThreadData->GetJSContextStack();
    JSContext* topJSContext;

    if(!stack || NS_FAILED(stack->Peek(&topJSContext)))
    {
        // If we don't have a stack we're probably in shutdown.
        NS_ASSERTION(!stack, "Bad, Peek failed!");
        mJSContext = nsnull;
        return;
    }

    if(!mJSContext)
    {
        // This is slightly questionable. If called without an explicit
        // JSContext (generally a call to a wrappedJS) we will use the JSContext
        // on the top of the JSContext stack - if there is one - *before*
        // falling back on the safe JSContext.
        // This is good AND bad because it makes calls from JS -> native -> JS
        // have JS stack 'continuity' for purposes of stack traces etc.
        // Note: this *is* what the pre-XPCCallContext xpconnect did too.

        if(topJSContext)
            mJSContext = topJSContext;
        else if(NS_FAILED(stack->GetSafeJSContext(&mJSContext)) || !mJSContext)
            return;
    }

    // Get into the request as early as we can to avoid problems with scanning
    // callcontexts on other threads from within the gc callbacks.

    if(mCallerLanguage == NATIVE_CALLER)
        JS_BeginRequest(mJSContext);

    if(topJSContext != mJSContext)
    {
        if(NS_FAILED(stack->Push(mJSContext)))
        {
            NS_ERROR("bad!");
            return;
        }
        mContextPopRequired = JS_TRUE;
    }

    mXPCContext = XPCContext::GetXPCContext(mJSContext);
    mPrevCallerLanguage = mXPCContext->SetCallingLangType(mCallerLanguage);

    // hook into call context chain for our thread
    mPrevCallContext = mThreadData->SetCallContext(this);

    // We only need to addref xpconnect once so only do it if this is the first
    // context in the chain.
    if(!mPrevCallContext)
        NS_ADDREF(mXPC);

    mState = HAVE_CONTEXT;

    if(!obj)
        return;

    mMethodIndex = 0xDEAD;
    mOperandJSObject = obj;

//.........这里部分代码省略.........

XPCCallContext::~XPCCallContext()
{
    // do cleanup...

    PRBool shouldReleaseXPC = PR_FALSE;

    if(mXPCContext)
    {
        mXPCContext->SetCallingLangType(mPrevCallerLanguage);

#ifdef DEBUG
        XPCCallContext* old = mThreadData->SetCallContext(mPrevCallContext);
        NS_ASSERTION(old == this, "bad pop from per thread data");
#else
        (void) mThreadData->SetCallContext(mPrevCallContext);
#endif

        shouldReleaseXPC = mPrevCallContext == nsnull;
    }

    if(mContextPopRequired)
    {
        XPCJSContextStack* stack = mThreadData->GetJSContextStack();
        NS_ASSERTION(stack, "bad!");
        if(stack)
        {
#ifdef DEBUG
            JSContext* poppedCX;
            nsresult rv = stack->Pop(&poppedCX);
            NS_ASSERTION(NS_SUCCEEDED(rv) && poppedCX == mJSContext, "bad pop");
#else
            (void) stack->Pop(nsnull);
#endif
        }
    }

    if(mJSContext)
    {
        if(mCallerLanguage == NATIVE_CALLER)
            JS_EndRequest(mJSContext);
        
        if(mDestroyJSContextInDestructor)
        {
#ifdef DEBUG_xpc_hacker
            printf("!xpc - doing deferred destruction of JSContext @ %0x\n", 
                   mJSContext);
#endif
            NS_ASSERTION(!mThreadData->GetJSContextStack() || 
                         !mThreadData->GetJSContextStack()->
                            DEBUG_StackHasJSContext(mJSContext),
                         "JSContext still in threadjscontextstack!");
        
            JS_DestroyContext(mJSContext);
        }
        else
        {
            // Don't clear newborns if JS frames (compilation or execution)
            // are active!  Doing so violates ancient invariants in the JS
            // engine, and it's not necessary to fix JS component leaks.
            if(!JS_IsRunning(mJSContext))
                JS_ClearNewbornRoots(mJSContext);
        }
    }

#ifdef DEBUG
    {
        StringWrapperEntry *se =
            reinterpret_cast<StringWrapperEntry*>(&mStringWrapperData);

        PRUint32 i;
        for(i = 0; i < XPCCCX_STRING_CACHE_SIZE; ++i)
        {
            NS_ASSERTION(!se[i].mInUse, "Uh, string wrapper still in use!");
        }
    }
#endif

    if(shouldReleaseXPC && mXPC)
        NS_RELEASE(mXPC);
}