LibWeb: Start fleshing out the ReadableStream interface

This is so we can just assume it exists in Fetch APIs (while still
skipping functionality that relies on a full implementation, of
course).

Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Streams/AbstractOperations.h>
+#include <LibWeb/Streams/ReadableStream.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#is-readable-stream-locked
+bool is_readable_stream_locked(ReadableStream const& stream)
+{
+    // 1. If stream.[[reader]] is undefined, return false.
+    if (stream.reader() == nullptr)
+        return false;
+
+    // 2. Return true.
+    return true;
+}
+
+}

Userland/Libraries/LibWeb/Streams/AbstractOperations.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/Forward.h>
+
+namespace Web::Streams {
+
+bool is_readable_stream_locked(ReadableStream const&);
+
+}

Userland/Libraries/LibWeb/Streams/ReadableStream.cpp

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/Window.h>
+#include <LibWeb/Streams/AbstractOperations.h>
+#include <LibWeb/Streams/ReadableStream.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#rs-constructor
+DOM::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> ReadableStream::create_with_global_object(HTML::Window& window)
+{
+    auto* readable_stream = window.heap().allocate<ReadableStream>(window.realm(), window);
+
+    return JS::NonnullGCPtr { *readable_stream };
+}
+
+ReadableStream::ReadableStream(HTML::Window& window)
+    : PlatformObject(window.realm())
+{
+    set_prototype(&window.cached_web_prototype("ReadableStream"));
+}
+
+ReadableStream::~ReadableStream() = default;
+
+void ReadableStream::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_controller);
+    visitor.visit(m_reader);
+    visitor.visit(m_stored_error);
+}
+
+// https://streams.spec.whatwg.org/#readablestream-locked
+bool ReadableStream::is_readable() const
+{
+    // A ReadableStream stream is readable if stream.[[state]] is "readable".
+    return m_state == State::Readable;
+}
+
+// https://streams.spec.whatwg.org/#readablestream-closed
+bool ReadableStream::is_closed() const
+{
+    // A ReadableStream stream is closed if stream.[[state]] is "closed".
+    return m_state == State::Closed;
+}
+
+// https://streams.spec.whatwg.org/#readablestream-errored
+bool ReadableStream::is_errored() const
+{
+    // A ReadableStream stream is errored if stream.[[state]] is "errored".
+    return m_state == State::Errored;
+}
+// https://streams.spec.whatwg.org/#readablestream-locked
+bool ReadableStream::is_locked() const
+{
+    // A ReadableStream stream is locked if ! IsReadableStreamLocked(stream) returns true.
+    return is_readable_stream_locked(*this);
+}
+
+// https://streams.spec.whatwg.org/#is-readable-stream-disturbed
+bool ReadableStream::is_disturbed() const
+{
+    // A ReadableStream stream is disturbed if stream.[[disturbed]] is true.
+    return m_disturbed;
+}
+
+}

Userland/Libraries/LibWeb/Streams/ReadableStream.h

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibJS/Forward.h>
+#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#readablestream
+class ReadableStream final : public Bindings::PlatformObject {
+    WEB_PLATFORM_OBJECT(Request, Bindings::PlatformObject);
+
+public:
+    enum class State {
+        Readable,
+        Closed,
+        Errored,
+    };
+
+    static DOM::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> create_with_global_object(HTML::Window&);
+
+    virtual ~ReadableStream() override;
+
+    JS::GCPtr<JS::Object> controller() const { return m_controller; }
+    JS::GCPtr<JS::Object> reader() const { return m_reader; }
+    JS::Value stored_error() const { return m_stored_error; }
+
+    bool is_readable() const;
+    bool is_closed() const;
+    bool is_errored() const;
+    bool is_locked() const;
+    bool is_disturbed() const;
+
+private:
+    explicit ReadableStream(HTML::Window&);
+
+    virtual void visit_edges(Cell::Visitor&) override;
+
+    // https://streams.spec.whatwg.org/#readablestream-controller
+    // A ReadableStreamDefaultController or ReadableByteStreamController created with the ability to control the state and queue of this stream
+    JS::GCPtr<JS::Object> m_controller;
+
+    // https://streams.spec.whatwg.org/#readablestream-detached
+    // A boolean flag set to true when the stream is transferred
+    bool m_detached { false };
+
+    // https://streams.spec.whatwg.org/#readablestream-disturbed
+    // A boolean flag set to true when the stream has been read from or canceled
+    bool m_disturbed { false };
+
+    // https://streams.spec.whatwg.org/#readablestream-reader
+    // A ReadableStreamDefaultReader or ReadableStreamBYOBReader instance, if the stream is locked to a reader, or undefined if it is not
+    JS::GCPtr<JS::Object> m_reader;
+
+    // https://streams.spec.whatwg.org/#readablestream-state
+    // A string containing the stream’s current state, used internally; one of "readable", "closed", or "errored"
+    State m_state { State::Readable };
+
+    // https://streams.spec.whatwg.org/#readablestream-storederror
+    // A value indicating how the stream failed, to be given as a failure reason or exception when trying to operate on an errored stream
+    JS::Value m_stored_error { JS::js_undefined() };
+};
+
+}

Userland/Libraries/LibWeb/Streams/ReadableStream.idl

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+// Dummy definition so we can use ReadableStream as a type in Fetch.
+
+// https://streams.spec.whatwg.org/#readablestream
+interface ReadableStream {
+};