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worker: make MessagePort uv_async_t inline field #26271

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worker: make MessagePort uv_async_t inline field #26271

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e463971
worker: remove MessagePort::AddToIncomingQueue
addaleax Feb 23, 2019
7c8f4c2
worker: make MessagePort `uv_async_t` inline field
addaleax Feb 23, 2019
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19 changes: 5 additions & 14 deletions src/node_messaging.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -469,18 +469,18 @@ MessagePort::MessagePort(Environment* env,
Local<Object> wrap)
: HandleWrap(env,
wrap,
reinterpret_cast<uv_handle_t*>(new uv_async_t()),
reinterpret_cast<uv_handle_t*>(&async_),
AsyncWrap::PROVIDER_MESSAGEPORT),
data_(new MessagePortData(this)) {
auto onmessage = [](uv_async_t* handle) {
// Called when data has been put into the queue.
MessagePort* channel = static_cast<MessagePort*>(handle->data);
MessagePort* channel = ContainerOf(&MessagePort::async_, handle);
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I wanted to ask this earlier as well - what is the consideration behind obtaining this through pointer arithmetic over the other one?

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For one, the address can't change; the contents of handle->data can.

In fact, the old code is mildly wrong because HandleWrap also sets handle_->data = this (where this is an instance of HandleWrap rather than MessagePort) so static_casting that to MessagePort afterwards would be wrong if multiple inheritance were involved.

channel->OnMessage();
};
CHECK_EQ(uv_async_init(env->event_loop(),
async(),
&async_,
onmessage), 0);
async()->data = static_cast<void*>(this);
async_.data = static_cast<void*>(this);

Local<Value> fn;
if (!wrap->Get(context, env->oninit_symbol()).ToLocal(&fn))
Expand All @@ -494,21 +494,13 @@ MessagePort::MessagePort(Environment* env,
Debug(this, "Created message port");
}

void MessagePort::AddToIncomingQueue(Message&& message) {
data_->AddToIncomingQueue(std::move(message));
}
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how is this change related?

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It’s not, it’s just something that I noticed, and putting it into another PR would have lead to yet another merge conflict. I’ve split it into a separate commit, as @bnoordhuis suggested.

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thanks. part of my question (which I meant to ask but did not come out like that) was why this change required at all - that is not covered in the PR description. But I got it now as: it is an unused piece of code.


uv_async_t* MessagePort::async() {
return reinterpret_cast<uv_async_t*>(GetHandle());
}

bool MessagePort::IsDetached() const {
return data_ == nullptr || IsHandleClosing();
}

void MessagePort::TriggerAsync() {
if (IsHandleClosing()) return;
CHECK_EQ(uv_async_send(async()), 0);
CHECK_EQ(uv_async_send(&async_), 0);
}

void MessagePort::Close(v8::Local<v8::Value> close_callback) {
Expand Down Expand Up @@ -643,7 +635,6 @@ void MessagePort::OnClose() {
data_->Disentangle();
}
data_.reset();
delete async();
}

std::unique_ptr<MessagePortData> MessagePort::Detach() {
Expand Down
4 changes: 1 addition & 3 deletions src/node_messaging.h
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Original file line number Diff line number Diff line change
Expand Up @@ -152,8 +152,6 @@ class MessagePort : public HandleWrap {
v8::Maybe<bool> PostMessage(Environment* env,
v8::Local<v8::Value> message,
v8::Local<v8::Value> transfer);
// Deliver a single message into this port's incoming queue.
void AddToIncomingQueue(Message&& message);

// Start processing messages on this port as a receiving end.
void Start();
Expand Down Expand Up @@ -200,9 +198,9 @@ class MessagePort : public HandleWrap {
void OnClose() override;
void OnMessage();
void TriggerAsync();
inline uv_async_t* async();

std::unique_ptr<MessagePortData> data_ = nullptr;
uv_async_t async_;

friend class MessagePortData;
};
Expand Down