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LibWeb+WebWorker: Use IPC mechanics for structured serialization

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Our structured serialization implementation had its own bespoke encoder
and decoder to serialize JS values. It also used a u32 buffer under the
hood, which made using its structures a bit awkward. We had previously
worked around its data structures in transferable streams, which nested
transfers of MessagePort instances. We basically had to add hooks into
the MessagePort to route to the correct transfer receiving steps, and
we could not invoke the correct AOs directly as the spec dictates.

We now use IPC mechanics to encode and decode data. This works because,
although we are encoding JS values, we are only ultimately encoding
primitive and basic AK types. The resulting data structures actually
enforce that we implement transferable streams exactly as the spec is
worded (I had planned to do that in a separate commit, but the fallout
of this patch actually required that change).
This commit is contained in:
Timothy Flynn 2025-07-17 09:51:04 -04:00 • committed by Tim Flynn
commit 64abc6101d
Notes: github-actions[bot] 2025-07-18 14:10:44 +00:00
44 changed files with 765 additions and 970 deletions
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43
Libraries/LibWeb/Streams/TransformStream.cpp
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@ -188,18 +188,11 @@ void TransformStream::set_up(GC::Ref<TransformAlgorithm> transform_algorithm, GC
}
// https://streams.spec.whatwg.org/#ref-for-transfer-steps②
WebIDL::ExceptionOr<void> TransformStream::transfer_steps(HTML::TransferDataHolder& data_holder)
WebIDL::ExceptionOr<void> TransformStream::transfer_steps(HTML::TransferDataEncoder& data_holder)
{
auto& realm = this->realm();
auto& vm = realm.vm();
auto serialize_stream = [&](auto stream) {
auto result = MUST(HTML::structured_serialize_with_transfer(vm, stream, { { GC::Root { stream } } }));
data_holder.data.extend(move(result.transfer_data_holders.first().data));
data_holder.fds.extend(move(result.transfer_data_holders.first().fds));
};
// 1. Let readable be value.[[readable]].
auto readable = this->readable();
@ -215,48 +208,32 @@ WebIDL::ExceptionOr<void> TransformStream::transfer_steps(HTML::TransferDataHold
return WebIDL::DataCloneError::create(realm, "Cannot transfer locked WritableStream"_string);
// 5. Set dataHolder.[[readable]] to ! StructuredSerializeWithTransfer(readable, « readable »).
serialize_stream(readable);
auto readable_result = MUST(HTML::structured_serialize_with_transfer(vm, readable, { { GC::Root { readable } } }));
data_holder.extend(move(readable_result.transfer_data_holders));
// 6. Set dataHolder.[[writable]] to ! StructuredSerializeWithTransfer(writable, « writable »).
serialize_stream(writable);
auto writable_result = MUST(HTML::structured_serialize_with_transfer(vm, writable, { { GC::Root { writable } } }));
data_holder.extend(move(writable_result.transfer_data_holders));
return {};
}
template<typename StreamType>
static WebIDL::ExceptionOr<GC::Ref<StreamType>> deserialize_stream(JS::Realm& realm, HTML::TransferDataHolder& data_holder)
{
auto transfer_type = data_holder.data.take_first();
if constexpr (IsSame<StreamType, ReadableStream>)
VERIFY(transfer_type == to_underlying(HTML::TransferType::ReadableStream));
else if constexpr (IsSame<StreamType, WritableStream>)
VERIFY(transfer_type == to_underlying(HTML::TransferType::WritableStream));
else
static_assert(DependentFalse<StreamType>);
auto stream = realm.create<StreamType>(realm);
TRY(stream->transfer_receiving_steps(data_holder));
return stream;
}
// https://streams.spec.whatwg.org/#ref-for-transfer-receiving-steps②
WebIDL::ExceptionOr<void> TransformStream::transfer_receiving_steps(HTML::TransferDataHolder& data_holder)
WebIDL::ExceptionOr<void> TransformStream::transfer_receiving_steps(HTML::TransferDataDecoder& data_holder)
{
auto& realm = this->realm();
// 1. Let readableRecord be ! StructuredDeserializeWithTransfer(dataHolder.[[readable]], the current Realm).
auto readable = TRY(deserialize_stream<ReadableStream>(realm, data_holder));
auto readable_record = MUST(HTML::structured_deserialize_with_transfer_internal(data_holder, realm));
// 2. Let writableRecord be ! StructuredDeserializeWithTransfer(dataHolder.[[writable]], the current Realm).
auto writable = TRY(deserialize_stream<WritableStream>(realm, data_holder));
auto writeable_record = MUST(HTML::structured_deserialize_with_transfer_internal(data_holder, realm));
// 3. Set value.[[readable]] to readableRecord.[[Deserialized]].
set_readable(readable);
set_readable(as<ReadableStream>(readable_record.as_object()));
// 4. Set value.[[writable]] to writableRecord.[[Deserialized]].
set_writable(writable);
set_writable(as<WritableStream>(writeable_record.as_object()));
// 5. Set value.[[backpressure]], value.[[backpressureChangePromise]], and value.[[controller]] to undefined.
set_backpressure({});