LibWeb+Meta: Add wrapper for the BufferSource/ArrayBufferView IDL types

These wrappers will make it much easier to do various operations on the
different ArrayBuffer-related classes in LibWeb compared to the current
solution, which is to just accept a Handle<Object> everywhere (and use
"any" in the *.idl files).

Co-Authored-By: Matthew Olsson <mattco@serenityos.org>

Userland/Libraries/LibWeb/WebIDL/Buffers.cpp

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2023, Shannon Booth <shannon@serenityos.org>
+ * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/DataView.h>
+#include <LibJS/Runtime/TypedArray.h>
+#include <LibWeb/WebIDL/Buffers.h>
+
+namespace Web::WebIDL {
+
+u32 BufferableObjectBase::byte_length() const
+{
+    return m_bufferable_object.visit([](auto& obj) { return static_cast<u32>(obj->byte_length()); });
+}
+
+JS::NonnullGCPtr<JS::Object> BufferableObjectBase::raw_object()
+{
+    return m_bufferable_object.visit([](auto const& obj) -> JS::NonnullGCPtr<JS::Object> { return obj; });
+}
+
+JS::GCPtr<JS::ArrayBuffer> BufferableObjectBase::viewed_array_buffer()
+{
+    return m_bufferable_object.visit(
+        [](JS::NonnullGCPtr<JS::ArrayBuffer> array_buffer) -> JS::GCPtr<JS::ArrayBuffer> { return array_buffer; },
+        [](auto const& view) -> JS::GCPtr<JS::ArrayBuffer> { return view->viewed_array_buffer(); });
+}
+
+BufferableObject BufferableObjectBase::bufferable_object_from_raw_object(JS::NonnullGCPtr<JS::Object> object)
+{
+    if (is<JS::TypedArrayBase>(*object))
+        return JS::NonnullGCPtr { static_cast<JS::TypedArrayBase&>(*object) };
+
+    if (is<JS::DataView>(*object))
+        return JS::NonnullGCPtr { static_cast<JS::DataView&>(*object) };
+
+    if (is<JS::ArrayBuffer>(*object))
+        return JS::NonnullGCPtr { static_cast<JS::ArrayBuffer&>(*object) };
+
+    VERIFY_NOT_REACHED();
+}
+
+BufferableObjectBase::BufferableObjectBase(JS::NonnullGCPtr<JS::Object> object)
+    : m_bufferable_object(bufferable_object_from_raw_object(object))
+{
+}
+
+bool BufferableObjectBase::is_typed_array_base() const
+{
+    return m_bufferable_object.has<JS::NonnullGCPtr<JS::TypedArrayBase>>();
+}
+
+bool BufferableObjectBase::is_data_view() const
+{
+    return m_bufferable_object.has<JS::NonnullGCPtr<JS::DataView>>();
+}
+
+bool BufferableObjectBase::is_array_buffer() const
+{
+    return m_bufferable_object.has<JS::NonnullGCPtr<JS::ArrayBuffer>>();
+}
+
+void BufferableObjectBase::visit_edges(Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    m_bufferable_object.visit([&](auto& obj) { visitor.visit(obj); });
+}
+
+ArrayBufferView::~ArrayBufferView() = default;
+
+u32 ArrayBufferView::byte_offset() const
+{
+    return m_bufferable_object.visit(
+        [](JS::NonnullGCPtr<JS::ArrayBuffer>) -> u32 { VERIFY_NOT_REACHED(); },
+        [](auto& view) -> u32 { return static_cast<u32>(view->byte_offset()); });
+}
+
+BufferSource::~BufferSource() = default;
+
+}

Userland/Libraries/LibWeb/WebIDL/Buffers.h

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2023, Shannon Booth <shannon@serenityos.org>
+ * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Variant.h>
+#include <LibJS/Forward.h>
+#include <LibJS/Heap/Cell.h>
+
+namespace Web::WebIDL {
+
+using BufferableObject = Variant<
+    JS::NonnullGCPtr<JS::TypedArrayBase>,
+    JS::NonnullGCPtr<JS::DataView>,
+    JS::NonnullGCPtr<JS::ArrayBuffer>>;
+
+class BufferableObjectBase : public JS::Cell {
+    JS_CELL(BufferableObjectBase, JS::Cell);
+
+public:
+    virtual ~BufferableObjectBase() override = default;
+
+    u32 byte_length() const;
+
+    JS::NonnullGCPtr<JS::Object> raw_object();
+    JS::GCPtr<JS::ArrayBuffer> viewed_array_buffer();
+
+    BufferableObject const& bufferable_object() const { return m_bufferable_object; }
+    BufferableObject& bufferable_object() { return m_bufferable_object; }
+
+protected:
+    BufferableObjectBase(JS::NonnullGCPtr<JS::Object>);
+
+    virtual void visit_edges(Visitor&) override;
+
+    bool is_data_view() const;
+    bool is_typed_array_base() const;
+    bool is_array_buffer() const;
+
+    static BufferableObject bufferable_object_from_raw_object(JS::NonnullGCPtr<JS::Object>);
+
+    BufferableObject m_bufferable_object;
+};
+
+// https://webidl.spec.whatwg.org/#ArrayBufferView
+//
+// typedef (Int8Array or Int16Array or Int32Array or
+//          Uint8Array or Uint16Array or Uint32Array or Uint8ClampedArray or
+//          BigInt64Array or BigUint64Array or
+//          Float32Array or Float64Array or DataView) ArrayBufferView;
+class ArrayBufferView : public BufferableObjectBase {
+    JS_CELL(ArrayBufferView, BufferableObjectBase);
+
+public:
+    using BufferableObjectBase::BufferableObjectBase;
+
+    virtual ~ArrayBufferView() override;
+
+    using BufferableObjectBase::is_data_view;
+    using BufferableObjectBase::is_typed_array_base;
+
+    u32 byte_offset() const;
+};
+
+// https://webidl.spec.whatwg.org/#BufferSource
+//
+// typedef (ArrayBufferView or ArrayBuffer) BufferSource;
+class BufferSource : public BufferableObjectBase {
+    JS_CELL(BufferSource, BufferableObjectBase);
+
+public:
+    using BufferableObjectBase::BufferableObjectBase;
+
+    virtual ~BufferSource() override;
+
+    using BufferableObjectBase::is_array_buffer;
+    using BufferableObjectBase::is_data_view;
+    using BufferableObjectBase::is_typed_array_base;
+};
+
+}