/* static */ void
ArrayBufferObject::sweep(JSCompartment *compartment)
{
JSRuntime *rt = compartment->runtimeFromMainThread();
ArrayBufferVector &gcLiveArrayBuffers = compartment->gcLiveArrayBuffers;
for (size_t i = 0; i < gcLiveArrayBuffers.length(); i++) {
ArrayBufferObject *buffer = gcLiveArrayBuffers[i];
JS_ASSERT(buffer->inLiveList());
buffer->setInLiveList(false);
ArrayBufferViewObject *viewsHead = buffer->viewList();
JS_ASSERT(viewsHead);
buffer->setViewList(UpdateObjectIfRelocated(rt, &viewsHead));
// Rebuild the list of views of the ArrayBufferObject, discarding dead
// views. If there is only one view, it will have already been marked.
ArrayBufferViewObject *prevLiveView = nullptr;
ArrayBufferViewObject *view = viewsHead;
while (view) {
JS_ASSERT(buffer->compartment() == view->compartment());
ArrayBufferViewObject *nextView = view->nextView();
if (!IsObjectAboutToBeFinalized(&view)) {
view->setNextView(prevLiveView);
prevLiveView = view;
}
view = UpdateObjectIfRelocated(rt, &nextView);
}
buffer->setViewList(prevLiveView);
}
gcLiveArrayBuffers.clear();
}
void
ArrayBufferObject::changeContents(JSContext *cx, void *newData)
{
// Change buffer contents.
uint8_t* oldDataPointer = dataPointer();
setNewOwnedData(cx->runtime()->defaultFreeOp(), newData);
// Update all views.
ArrayBufferViewObject *viewListHead = viewList();
for (ArrayBufferViewObject *view = viewListHead; view; view = view->nextView()) {
// Watch out for NULL data pointers in views. This means that the view
// is not fully initialized (in which case it'll be initialized later
// with the correct pointer).
uint8_t *viewDataPointer = view->dataPointer();
if (viewDataPointer) {
JS_ASSERT(newData);
ptrdiff_t offset = viewDataPointer - oldDataPointer;
viewDataPointer = static_cast<uint8_t *>(newData) + offset;
view->setPrivate(viewDataPointer);
}
// Notify compiled jit code that the base pointer has moved.
MarkObjectStateChange(cx, view);
}
}
void
ArrayBufferObject::changeContents(JSContext *cx, void *newData)
{
JS_ASSERT(!isAsmJSArrayBuffer());
JS_ASSERT(!isSharedArrayBuffer());
// Update all views.
ArrayBufferViewObject *viewListHead = viewList();
for (ArrayBufferViewObject *view = viewListHead; view; view = view->nextView()) {
// Watch out for NULL data pointers in views. This either
// means that the view is not fully initialized (in which case
// it'll be initialized later with the correct pointer) or
// that the view has been neutered. In that case, the buffer
// is "en route" to being neutered but the isNeuteredBuffer()
// flag may not yet be set.
uint8_t *viewDataPointer = view->dataPointer();
if (viewDataPointer) {
JS_ASSERT(newData);
viewDataPointer += static_cast<uint8_t *>(newData) - dataPointer();
view->setPrivate(viewDataPointer);
}
// Notify compiled jit code that the base pointer has moved.
MarkObjectStateChange(cx, view);
}
if (ownsData())
releaseData(cx->runtime()->defaultFreeOp());
setDataPointer(static_cast<uint8_t *>(newData), OwnsData);
}
/* static */ void
ArrayBufferObject::obj_trace(JSTracer *trc, JSObject *obj)
{
if (!IS_GC_MARKING_TRACER(trc) && !trc->runtime()->isHeapMinorCollecting()
#ifdef JSGC_FJGENERATIONAL
&& !trc->runtime()->isFJMinorCollecting()
#endif
)
{
return;
}
// ArrayBufferObjects need to maintain a list of possibly-weak pointers to
// their views. The straightforward way to update the weak pointers would
// be in the views' finalizers, but giving views finalizers means they
// cannot be swept in the background. This results in a very high
// performance cost. Instead, ArrayBufferObjects with a single view hold a
// strong pointer to the view. This can entrain garbage when the single
// view becomes otherwise unreachable while the buffer is still live, but
// this is expected to be rare. ArrayBufferObjects with 0-1 views are
// expected to be by far the most common cases. ArrayBufferObjects with
// multiple views are collected into a linked list during collection, and
// then swept to prune out their dead views.
ArrayBufferObject &buffer = AsArrayBuffer(obj);
ArrayBufferViewObject *viewsHead = buffer.viewList();
if (!viewsHead)
return;
buffer.setViewList(UpdateObjectIfRelocated(trc->runtime(), &viewsHead));
if (viewsHead->nextView() == nullptr) {
// Single view: mark it, but only if we're actually doing a GC pass
// right now. Otherwise, the tracing pass for barrier verification will
// fail if we add another view and the pointer becomes weak.
MarkObjectUnbarriered(trc, &viewsHead, "arraybuffer.singleview");
buffer.setViewListNoBarrier(viewsHead);
} else {
// Multiple views: do not mark, but append buffer to list.
ArrayBufferVector &gcLiveArrayBuffers = buffer.compartment()->gcLiveArrayBuffers;
// obj_trace may be called multiple times before sweep(), so avoid
// adding this buffer to the list multiple times.
if (buffer.inLiveList()) {
#ifdef DEBUG
bool found = false;
for (size_t i = 0; i < gcLiveArrayBuffers.length(); i++)
found |= gcLiveArrayBuffers[i] == &buffer;
JS_ASSERT(found);
#endif
} else if (gcLiveArrayBuffers.append(&buffer)) {
buffer.setInLiveList(true);
} else {
CrashAtUnhandlableOOM("OOM while updating live array buffers");
}
}
}
/* static */ void
ArrayBufferObject::neuter(JSContext *cx, Handle<ArrayBufferObject*> buffer, void *newData)
{
JS_ASSERT(buffer->canNeuter(cx));
// Neuter all views on the buffer, clear out the list of views and the
// buffer's data.
for (ArrayBufferViewObject *view = buffer->viewList(); view; view = view->nextView()) {
view->neuter(newData);
// Notify compiled jit code that the base pointer has moved.
MarkObjectStateChange(cx, view);
}
if (newData != buffer->dataPointer())
buffer->setNewOwnedData(cx->runtime()->defaultFreeOp(), newData);
buffer->setByteLength(0);
buffer->setViewList(nullptr);
buffer->setIsNeutered();
// If this is happening during an incremental GC, remove the buffer from
// the list of live buffers with multiple views if necessary.
if (buffer->inLiveList()) {
ArrayBufferVector &gcLiveArrayBuffers = cx->compartment()->gcLiveArrayBuffers;
DebugOnly<bool> found = false;
for (size_t i = 0; i < gcLiveArrayBuffers.length(); i++) {
if (buffer == gcLiveArrayBuffers[i]) {
found = true;
gcLiveArrayBuffers[i] = gcLiveArrayBuffers.back();
gcLiveArrayBuffers.popBack();
break;
}
}
JS_ASSERT(found);
buffer->setInLiveList(false);
}
}