gecko-dev/dom/base/nsWrapperCacheInlines.h

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C

/* -*- 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/. */
#ifndef nsWrapperCacheInline_h___
#define nsWrapperCacheInline_h___
#include "nsWrapperCache.h"
#include "js/GCAPI.h"
#include "js/TracingAPI.h"
inline JSObject*
nsWrapperCache::GetWrapperPreserveColor() const
{
JSObject* obj = mWrapper;
if (obj && js::gc::EdgeNeedsSweepUnbarriered(&obj)) {
// The object has been found to be dead and is in the process of being
// finalized, so don't let the caller see it. As an optimisation, remove it
// from the cache so we don't have to do this check in future.
const_cast<nsWrapperCache*>(this)->ClearWrapper();
return nullptr;
}
MOZ_ASSERT(obj == mWrapper);
return obj;
}
inline JSObject*
nsWrapperCache::GetWrapper() const
{
JSObject* obj = GetWrapperPreserveColor();
if (obj) {
JS::ExposeObjectToActiveJS(obj);
}
return obj;
}
inline bool
nsWrapperCache::HasKnownLiveWrapper() const
{
// If we have a wrapper and it's not gray in the GC-marking sense, that means
// that we can't be cycle-collected. That's because the wrapper is being kept
// alive by the JS engine (and not just due to being traced from some
// cycle-collectable thing), and the wrapper holds us alive, so we know we're
// not collectable.
JSObject* o = GetWrapperPreserveColor();
return o && !JS::ObjectIsMarkedGray(o);
}
static void
SearchGray(JS::GCCellPtr aGCThing, const char* aName, void* aClosure)
{
bool* hasGrayObjects = static_cast<bool*>(aClosure);
if (!*hasGrayObjects && aGCThing && JS::GCThingIsMarkedGray(aGCThing)) {
*hasGrayObjects = true;
}
}
inline bool
nsWrapperCache::HasNothingToTrace(nsISupports* aThis)
{
nsXPCOMCycleCollectionParticipant* participant = nullptr;
CallQueryInterface(aThis, &participant);
bool hasGrayObjects = false;
participant->Trace(aThis, TraceCallbackFunc(SearchGray), &hasGrayObjects);
return !hasGrayObjects;
}
inline bool
nsWrapperCache::HasKnownLiveWrapperAndDoesNotNeedTracing(nsISupports* aThis)
{
return HasKnownLiveWrapper() && HasNothingToTrace(aThis);
}
inline void
nsWrapperCache::MarkWrapperLive()
{
// Just call GetWrapper and ignore the return value. It will do the
// gray-unmarking for us.
GetWrapper();
}
#endif /* nsWrapperCache_h___ */