LibWeb/Streams: Fully implement BYOB operations for ReadableStream

As far as I can tell there is no change in WPT from this implementation.
But these steps should be more effecient than using the non BYOB steps
as we can make direct use of the provided buffer to the byte stream.

Libraries/LibWeb/Streams/ReadableStream.cpp

@@ -15,9 +15,12 @@
 #include <LibWeb/Streams/ReadableByteStreamController.h>
 #include <LibWeb/Streams/ReadableStream.h>
 #include <LibWeb/Streams/ReadableStreamBYOBReader.h>
+#include <LibWeb/Streams/ReadableStreamBYOBRequest.h>
 #include <LibWeb/Streams/ReadableStreamDefaultController.h>
 #include <LibWeb/Streams/ReadableStreamDefaultReader.h>
 #include <LibWeb/Streams/UnderlyingSource.h>
+#include <LibWeb/Streams/WritableStream.h>
+#include <LibWeb/WebIDL/Buffers.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Streams {
@@ -280,8 +283,10 @@ WebIDL::ExceptionOr<void> ReadableStream::pull_from_bytes(ByteBuffer bytes)
     // 3. Let desiredSize be available.
     auto desired_size = available;
 
-    // FIXME: 4. If stream’s current BYOB request view is non-null, then set desiredSize to stream’s current BYOB request
+    // 4. If stream’s current BYOB request view is non-null, then set desiredSize to stream’s current BYOB request
     //    view's byte length.
+    if (auto byob_view = current_byob_request_view())
+        desired_size = byob_view->byte_length();
 
     // 5. Let pullSize be the smaller value of available and desiredSize.
     auto pull_size = min(available, desired_size);
@@ -293,11 +298,16 @@ WebIDL::ExceptionOr<void> ReadableStream::pull_from_bytes(ByteBuffer bytes)
     if (pull_size != available)
         bytes = MUST(bytes.slice(pull_size, available - pull_size));
 
-    // FIXME: 8. If stream’s current BYOB request view is non-null, then:
+    // 8. If stream’s current BYOB request view is non-null, then:
+    if (auto byob_view = current_byob_request_view()) {
         // 1. Write pulled into stream’s current BYOB request view.
+        byob_view->write(pulled);
+
         // 2. Perform ? ReadableByteStreamControllerRespond(stream.[[controller]], pullSize).
+        TRY(readable_byte_stream_controller_respond(controller, pull_size));
+    }
     // 9. Otherwise,
-    {
+    else {
         // 1. Set view to the result of creating a Uint8Array from pulled in stream’s relevant Realm.
         auto array_buffer = JS::ArrayBuffer::create(realm, move(pulled));
         auto view = JS::Uint8Array::create(realm, array_buffer->byte_length(), *array_buffer);
@@ -309,6 +319,23 @@ WebIDL::ExceptionOr<void> ReadableStream::pull_from_bytes(ByteBuffer bytes)
     return {};
 }
 
+// https://streams.spec.whatwg.org/#readablestream-current-byob-request-view
+GC::Ptr<WebIDL::ArrayBufferView> ReadableStream::current_byob_request_view()
+{
+    // 1. Assert: stream.[[controller]] implements ReadableByteStreamController.
+    VERIFY(m_controller->has<GC::Ref<ReadableByteStreamController>>());
+
+    // 2. Let byobRequest be ! ReadableByteStreamControllerGetBYOBRequest(stream.[[controller]]).
+    auto byob_request = readable_byte_stream_controller_get_byob_request(m_controller->get<GC::Ref<ReadableByteStreamController>>());
+
+    // 3. If byobRequest is null, then return null.
+    if (!byob_request)
+        return {};
+
+    // 4. Return byobRequest.[[view]].
+    return byob_request->view();
+}
+
 // https://streams.spec.whatwg.org/#readablestream-enqueue
 WebIDL::ExceptionOr<void> ReadableStream::enqueue(JS::Value chunk)
 {
@@ -317,7 +344,7 @@ WebIDL::ExceptionOr<void> ReadableStream::enqueue(JS::Value chunk)
     // 1. If stream.[[controller]] implements ReadableStreamDefaultController,
     if (m_controller->has<GC::Ref<ReadableStreamDefaultController>>()) {
         // 1. Perform ! ReadableStreamDefaultControllerEnqueue(stream.[[controller]], chunk).
-        return readable_stream_default_controller_enqueue(m_controller->get<GC::Ref<ReadableStreamDefaultController>>(), chunk);
+        MUST(readable_stream_default_controller_enqueue(m_controller->get<GC::Ref<ReadableStreamDefaultController>>(), chunk));
     }
     // 2. Otherwise,
     else {
@@ -325,23 +352,31 @@ WebIDL::ExceptionOr<void> ReadableStream::enqueue(JS::Value chunk)
         VERIFY(m_controller->has<GC::Ref<ReadableByteStreamController>>());
         auto readable_byte_controller = m_controller->get<GC::Ref<ReadableByteStreamController>>();
 
-        // FIXME: 2. Assert: chunk is an ArrayBufferView.
+        // 2. Assert: chunk is an ArrayBufferView.
+        VERIFY(chunk.is_object());
+        auto chunk_view = heap().allocate<WebIDL::ArrayBufferView>(chunk.as_object());
 
         // 3. Let byobView be the current BYOB request view for stream.
-        // FIXME: This is not what the spec means by 'current BYOB request view'
+        auto byob_view = current_byob_request_view();
-        auto byob_view = readable_byte_controller->raw_byob_request();
 
         // 4. If byobView is non-null, and chunk.[[ViewedArrayBuffer]] is byobView.[[ViewedArrayBuffer]], then:
-        if (byob_view) {
+        if (byob_view && chunk_view->viewed_array_buffer() == byob_view->viewed_array_buffer()) {
-            // FIXME: 1. Assert: chunk.[[ByteOffset]] is byobView.[[ByteOffset]].
+            // 1. Assert: chunk.[[ByteOffset]] is byobView.[[ByteOffset]].
-            // FIXME: 2. Assert: chunk.[[ByteLength]] ≤ byobView.[[ByteLength]].
+            VERIFY(chunk_view->byte_offset() == byob_view->byte_offset());
-            // FIXME: 3. Perform ? ReadableByteStreamControllerRespond(stream.[[controller]], chunk.[[ByteLength]]).
+
-            TODO();
+            // 2. Assert: chunk.[[ByteLength]] ≤ byobView.[[ByteLength]].
+            VERIFY(chunk_view->byte_length() <= byob_view->byte_length());
+
+            // 3. Perform ? ReadableByteStreamControllerRespond(stream.[[controller]], chunk.[[ByteLength]]).
+            TRY(readable_byte_stream_controller_respond(readable_byte_controller, chunk_view->byte_length()));
+        }
+        // 5. Otherwise, perform ? ReadableByteStreamControllerEnqueue(stream.[[controller]], chunk).
+        else {
+            TRY(readable_byte_stream_controller_enqueue(readable_byte_controller, chunk));
+        }
     }
 
-        // 5. Otherwise, perform ? ReadableByteStreamControllerEnqueue(stream.[[controller]], chunk).
+    return {};
-        return readable_byte_stream_controller_enqueue(readable_byte_controller, chunk);
-    }
 }
 
 // https://streams.spec.whatwg.org/#readablestream-set-up-with-byte-reading-support

Libraries/LibWeb/Streams/ReadableStream.h

@@ -111,6 +111,8 @@ public:
     void set_up_with_byte_reading_support(GC::Ptr<PullAlgorithm> = {}, GC::Ptr<CancelAlgorithm> = {}, double high_water_mark = 0);
     GC::Ref<WebIDL::Promise> piped_through(GC::Ref<WritableStream>, bool prevent_close = false, bool prevent_abort = false, bool prevent_cancel = false, JS::Value signal = JS::js_undefined());
 
+    GC::Ptr<WebIDL::ArrayBufferView> current_byob_request_view();
+
 private:
     explicit ReadableStream(JS::Realm&);