XPCCallContext.cpp

/* -*- 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/. */

/* Call context. */

#include "xpcprivate.h"
#include "jsfriendapi.h"
#include "js/Object.h"  // JS::GetClass, JS::GetReservedSlot
#include "js/Wrapper.h"
#include "nsContentUtils.h"

using namespace mozilla;
using namespace xpc;
using namespace JS;

static inline bool IsTearoffClass(const JSClass* clazz) {
  return clazz == &XPC_WN_Tearoff_JSClass;
}

XPCCallContext::XPCCallContext(
    JSContext* cx, HandleObject obj /* = nullptr               */,
    HandleObject funobj /* = nullptr               */,
    HandleId name /* = JSID_VOID             */, unsigned argc /* = NO_ARGS */,
    Value* argv /* = nullptr */, Value* rval /* = nullptr               */)
    : mState(INIT_FAILED),
      mXPC(nsXPConnect::XPConnect()),
      mXPCJSContext(nullptr),
      mJSContext(cx),
      mWrapper(nullptr),
      mTearOff(nullptr),
      mMember(nullptr),
      mName(cx),
      mStaticMemberIsLocal(false),
      mArgc(0),
      mArgv(nullptr),
      mRetVal(nullptr) {
  MOZ_ASSERT(cx);
  MOZ_ASSERT(cx == nsContentUtils::GetCurrentJSContext());

  if (!mXPC) {
    return;
  }

  mXPCJSContext = XPCJSContext::Get();

  // hook into call context chain.
  mPrevCallContext = mXPCJSContext->SetCallContext(this);

  mState = HAVE_CONTEXT;

  if (!obj) {
    return;
  }

  mMethodIndex = 0xDEAD;

  mState = HAVE_OBJECT;

  mTearOff = nullptr;

  JSObject* unwrapped =
      js::CheckedUnwrapDynamic(obj, cx, /* stopAtWindowProxy = */ false);
  if (!unwrapped) {
    JS_ReportErrorASCII(mJSContext,
                        "Permission denied to call method on |this|");
    mState = INIT_FAILED;
    return;
  }
  const JSClass* clasp = JS::GetClass(unwrapped);
  if (clasp->isWrappedNative()) {
    mWrapper = XPCWrappedNative::Get(unwrapped);
  } else if (IsTearoffClass(clasp)) {
    mTearOff = XPCWrappedNativeTearOff::Get(unwrapped);
    mWrapper = XPCWrappedNative::Get(
        &JS::GetReservedSlot(unwrapped, XPCWrappedNativeTearOff::FlatObjectSlot)
             .toObject());
  }
  if (mWrapper && !mTearOff) {
    mScriptable = mWrapper->GetScriptable();
  }

  if (!name.isVoid()) {
    SetName(name);
  }

  if (argc != NO_ARGS) {
    SetArgsAndResultPtr(argc, argv, rval);
  }

  CHECK_STATE(HAVE_OBJECT);
}

void XPCCallContext::SetName(jsid name) {
  CHECK_STATE(HAVE_OBJECT);

  mName = name;

  if (mTearOff) {
    mSet = nullptr;
    mInterface = mTearOff->GetInterface();
    mMember = mInterface->FindMember(mName);
    mStaticMemberIsLocal = true;
    if (mMember && !mMember->IsConstant()) {
      mMethodIndex = mMember->GetIndex();
    }
  } else {
    mSet = mWrapper ? mWrapper->GetSet() : nullptr;

    if (mSet &&
        mSet->FindMember(
            mName, &mMember, &mInterface,
            mWrapper->HasProto() ? mWrapper->GetProto()->GetSet() : nullptr,
            &mStaticMemberIsLocal)) {
      if (mMember && !mMember->IsConstant()) {
        mMethodIndex = mMember->GetIndex();
      }
    } else {
      mMember = nullptr;
      mInterface = nullptr;
      mStaticMemberIsLocal = false;
    }
  }

  mState = HAVE_NAME;
}

void XPCCallContext::SetCallInfo(XPCNativeInterface* iface,
                                 XPCNativeMember* member, bool isSetter) {
  CHECK_STATE(HAVE_CONTEXT);

  // We are going straight to the method info and need not do a lookup
  // by id.

  // don't be tricked if method is called with wrong 'this'
  if (mTearOff && mTearOff->GetInterface() != iface) {
    mTearOff = nullptr;
  }

  mSet = nullptr;
  mInterface = iface;
  mMember = member;
  mMethodIndex = mMember->GetIndex() + (isSetter ? 1 : 0);
  mName = mMember->GetName();

  if (mState < HAVE_NAME) {
    mState = HAVE_NAME;
  }
}

void XPCCallContext::SetArgsAndResultPtr(unsigned argc, Value* argv,
                                         Value* rval) {
  CHECK_STATE(HAVE_OBJECT);

  if (mState < HAVE_NAME) {
    mSet = nullptr;
    mInterface = nullptr;
    mMember = nullptr;
    mStaticMemberIsLocal = false;
  }

  mArgc = argc;
  mArgv = argv;
  mRetVal = rval;

  mState = HAVE_ARGS;
}

nsresult XPCCallContext::CanCallNow() {
  nsresult rv;

  if (!HasInterfaceAndMember()) {
    return NS_ERROR_UNEXPECTED;
  }
  if (mState < HAVE_ARGS) {
    return NS_ERROR_UNEXPECTED;
  }

  if (!mTearOff) {
    mTearOff = mWrapper->FindTearOff(mJSContext, mInterface, false, &rv);
    if (!mTearOff || mTearOff->GetInterface() != mInterface) {
      mTearOff = nullptr;
      return NS_FAILED(rv) ? rv : NS_ERROR_UNEXPECTED;
    }
  }

  // Refresh in case FindTearOff extended the set
  mSet = mWrapper->GetSet();

  mState = READY_TO_CALL;
  return NS_OK;
}

void XPCCallContext::SystemIsBeingShutDown() {
  // XXX This is pretty questionable since the per thread cleanup stuff
  // can be making this call on one thread for call contexts on another
  // thread.
  NS_WARNING(
      "Shutting Down XPConnect even through there is a live XPCCallContext");
  mXPCJSContext = nullptr;
  mState = SYSTEM_SHUTDOWN;
  mSet = nullptr;
  mInterface = nullptr;

  if (mPrevCallContext) {
    mPrevCallContext->SystemIsBeingShutDown();
  }
}

XPCCallContext::~XPCCallContext() {
  if (mXPCJSContext) {
    DebugOnly<XPCCallContext*> old =
        mXPCJSContext->SetCallContext(mPrevCallContext);
    MOZ_ASSERT(old == this, "bad pop from per thread data");
  }
}