LibWeb: Mostly implement ReadableByteStreamController.[[PullSteps]]

Userland/Libraries/LibWeb/Streams/ReadableByteStreamController.cpp

@@ -7,6 +7,7 @@
 #include <LibWeb/Streams/ReadableByteStreamController.h>
 #include <LibWeb/Streams/ReadableStream.h>
 #include <LibWeb/Streams/ReadableStreamBYOBRequest.h>
+#include <LibWeb/Streams/ReadableStreamDefaultReader.h>
 
 namespace Web::Streams {
 
@@ -41,6 +42,70 @@ WebIDL::ExceptionOr<JS::GCPtr<WebIDL::Promise>> ReadableByteStreamController::ca
     return result;
 }
 
+// https://streams.spec.whatwg.org/#rbs-controller-private-pull
+WebIDL::ExceptionOr<void> ReadableByteStreamController::pull_steps(NonnullRefPtr<ReadRequest> read_request)
+{
+    auto& vm = this->vm();
+    auto& realm = this->realm();
+
+    // 1. Let stream be this.[[stream]].
+
+    // 2. Assert: ! ReadableStreamHasDefaultReader(stream) is true.
+    VERIFY(readable_stream_has_default_reader(*m_stream));
+
+    // 3. If this.[[queueTotalSize]] > 0,
+    if (m_queue_total_size > 0) {
+        // 1. Assert: ! ReadableStreamGetNumReadRequests(stream) is 0.
+        VERIFY(readable_stream_get_num_read_requests(*m_stream) == 0);
+
+        // 2. Perform ! ReadableByteStreamControllerFillReadRequestFromQueue(this, readRequest).
+        TRY(readable_byte_stream_controller_fill_read_request_from_queue(*this, read_request));
+
+        // 3. Return.
+        return {};
+    }
+
+    // 4. Let autoAllocateChunkSize be this.[[autoAllocateChunkSize]].
+
+    // 5. If autoAllocateChunkSize is not undefined,
+    if (m_auto_allocate_chunk_size.has_value()) {
+        // 1. Let buffer be Construct(%ArrayBuffer%, « autoAllocateChunkSize »).
+        auto buffer = JS::ArrayBuffer::create(realm, *m_auto_allocate_chunk_size);
+
+        // 2. If buffer is an abrupt completion,
+        if (buffer.is_throw_completion()) {
+            // 1. Perform readRequest’s error steps, given buffer.[[Value]].
+            read_request->on_error(*buffer.throw_completion().value());
+
+            // 2. Return.
+            return {};
+        }
+
+        // 3. Let pullIntoDescriptor be a new pull-into descriptor with buffer buffer.[[Value]], buffer byte length autoAllocateChunkSize, byte offset 0,
+        //    byte length autoAllocateChunkSize, bytes filled 0, element size 1, view constructor %Uint8Array%, and reader type "default".
+        PullIntoDescriptor pull_into_descriptor {
+            .buffer = buffer.release_value(),
+            .buffer_byte_length = *m_auto_allocate_chunk_size,
+            .byte_offset = 0,
+            .byte_length = *m_auto_allocate_chunk_size,
+            .bytes_filled = 0,
+            .element_size = 1,
+            .view_constructor = *realm.intrinsics().uint8_array_constructor(),
+            .reader_type = ReaderType::Default,
+        };
+
+        // 4. Append pullIntoDescriptor to this.[[pendingPullIntos]].
+        TRY_OR_THROW_OOM(vm, m_pending_pull_intos.try_append(move(pull_into_descriptor)));
+    }
+
+    // 6. Perform ! ReadableStreamAddReadRequest(stream, readRequest).
+    readable_stream_add_read_request(*m_stream, read_request);
+
+    // FIXME: 7. Perform ! ReadableByteStreamControllerCallPullIfNeeded(this).
+
+    return {};
+}
+
 void ReadableByteStreamController::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);