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LibWeb: Implement ReadableStreamPipeTo according to spec

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Our existing implementation of stream piping was extremely ad-hoc. It
did nothing to handle closed/errored streams, and did not read from or
write to streams in a way required by the spec.

This new implementation uses a custom JS::Cell to drive the read/write
loop.
This commit is contained in:
Timothy Flynn 2025-04-09 12:01:51 -04:00 • committed by Tim Flynn
commit eb0a51faf0
Notes: github-actions[bot] 2025-04-11 16:11:49 +00:00
33 changed files with 3926 additions and 85 deletions
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37
Libraries/LibWeb/Streams/ReadableStreamDefaultReader.cpp
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@ -66,6 +66,7 @@ void ReadableStreamDefaultReader::visit_edges(Cell::Visitor& visitor)
ReadableStreamGenericReaderMixin::visit_edges(visitor);
for (auto& request : m_read_requests)
visitor.visit(request);
visitor.visit(m_readable_stream_pipe_to_operation);
}
// https://streams.spec.whatwg.org/#read-loop
@ -212,42 +213,6 @@ void ReadableStreamDefaultReader::read_all_bytes(GC::Ref<ReadLoopReadRequest::Su
readable_stream_default_reader_read(*this, read_request);
}
void ReadableStreamDefaultReader::read_all_chunks(GC::Ref<ReadAllOnChunkSteps> chunk_steps, GC::Ref<ReadAllOnSuccessSteps> success_steps, GC::Ref<ReadAllOnFailureSteps> failure_steps)
{
// AD-HOC: Some spec steps direct us to "read all chunks" from a stream, but there isn't an AO defined to do that.
// We implement those steps by continuously making default read requests, which is an identity transformation,
// with a custom callback to receive each chunk that is read. This is done until the controller signals
// that there are no more chunks to consume.
// This function is based on "read_all_bytes" above.
auto promise_capability = read();
WebIDL::react_to_promise(
promise_capability,
GC::create_function(heap(), [this, chunk_steps, success_steps, failure_steps](JS::Value value) -> WebIDL::ExceptionOr<JS::Value> {
auto& vm = this->vm();
VERIFY(value.is_object());
auto& value_object = value.as_object();
auto done = MUST(JS::iterator_complete(vm, value_object));
if (!done) {
auto chunk = MUST(JS::iterator_value(vm, value_object));
chunk_steps->function()(chunk);
read_all_chunks(chunk_steps, success_steps, failure_steps);
} else {
success_steps->function()();
}
return JS::js_undefined();
}),
GC::create_function(heap(), [failure_steps](JS::Value error) -> WebIDL::ExceptionOr<JS::Value> {
failure_steps->function()(error);
return JS::js_undefined();
}));
}
// FIXME: This function is a promise-based wrapper around "read all bytes". The spec changed this function to not use promises
// in https://github.com/whatwg/streams/commit/f894acdd417926a2121710803cef593e15127964 - however, it seems that the
// FileAPI blob specification has not been updated to match, see: https://github.com/w3c/FileAPI/issues/187.