LibWeb: Add ReadableStreamDefaultReader

Userland/Libraries/LibWeb/Streams/ReadableStreamDefaultReader.cpp

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Runtime/Error.h>
+#include <LibJS/Runtime/IteratorOperations.h>
+#include <LibJS/Runtime/PromiseCapability.h>
+#include <LibJS/Runtime/Realm.h>
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/Bindings/ReadableStreamDefaultReaderPrototype.h>
+#include <LibWeb/Streams/AbstractOperations.h>
+#include <LibWeb/Streams/ReadableStream.h>
+#include <LibWeb/Streams/ReadableStreamDefaultReader.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+#include <LibWeb/WebIDL/Promise.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#default-reader-constructor
+WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStreamDefaultReader>> ReadableStreamDefaultReader::construct_impl(JS::Realm& realm, JS::NonnullGCPtr<ReadableStream> stream)
+{
+    auto reader = TRY(realm.heap().allocate<ReadableStreamDefaultReader>(realm, realm));
+
+    // 1. Perform ? SetUpReadableStreamDefaultReader(this, stream);
+    TRY(set_up_readable_stream_default_reader(reader, *stream));
+
+    return reader;
+}
+
+ReadableStreamDefaultReader::ReadableStreamDefaultReader(JS::Realm& realm)
+    : Bindings::PlatformObject(realm)
+{
+}
+
+JS::ThrowCompletionOr<void> ReadableStreamDefaultReader::initialize(JS::Realm& realm)
+{
+    MUST_OR_THROW_OOM(Base::initialize(realm));
+    set_prototype(&Bindings::ensure_web_prototype<Bindings::ReadableStreamDefaultReaderPrototype>(realm, "ReadableStreamDefaultReader"));
+
+    return {};
+}
+
+void ReadableStreamDefaultReader::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    ReadableStreamGenericReaderMixin::visit_edges(visitor);
+}
+
+class DefaultReaderReadRequest : public ReadRequest {
+public:
+    DefaultReaderReadRequest(JS::Realm& realm, WebIDL::Promise& promise)
+        : m_realm(realm)
+        , m_promise(promise)
+    {
+    }
+
+    virtual void on_chunk(JS::Value chunk) override
+    {
+        WebIDL::resolve_promise(m_realm, m_promise, JS::create_iterator_result_object(m_realm.vm(), chunk, false));
+    }
+
+    virtual void on_close() override
+    {
+        WebIDL::resolve_promise(m_realm, m_promise, JS::create_iterator_result_object(m_realm.vm(), JS::js_undefined(), true));
+    }
+
+    virtual void on_error(JS::Value error) override
+    {
+        WebIDL::reject_promise(m_realm, m_promise, error);
+    }
+
+private:
+    JS::Realm& m_realm;
+    WebIDL::Promise& m_promise;
+};
+
+// https://streams.spec.whatwg.org/#default-reader-read
+WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::Promise>> ReadableStreamDefaultReader::read()
+{
+    auto& realm = this->realm();
+
+    // 1. If this.[[stream]] is undefined, return a promise rejected with a TypeError exception.
+    if (!m_stream) {
+        auto exception = TRY(JS::TypeError::create(realm, "Cannot read from an empty stream"sv));
+        auto promise_capability = WebIDL::create_rejected_promise(realm, exception);
+        return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
+    }
+
+    // 2. Let promise be a new promise.
+    auto promise_capability = WebIDL::create_promise(realm);
+
+    // 3. Let readRequest be a new read request with the following items:
+    //    chunk steps, given chunk
+    //        Resolve promise with «[ "value" → chunk, "done" → false ]».
+    //    close steps
+    //        Resolve promise with «[ "value" → undefined, "done" → true ]».
+    //    error steps, given e
+    //        Reject promise with e.
+    auto read_request = adopt_ref(*new DefaultReaderReadRequest(realm, promise_capability));
+
+    // 4. Perform ! ReadableStreamDefaultReaderRead(this, readRequest).
+    readable_stream_default_reader_read(*this, read_request);
+
+    // 5. Return promise.
+    return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise()) };
+}
+
+// https://streams.spec.whatwg.org/#default-reader-release-lock
+WebIDL::ExceptionOr<void> ReadableStreamDefaultReader::release_lock()
+{
+    // 1. If this.[[stream]] is undefined, return.
+    if (!m_stream)
+        return {};
+
+    // 2. Perform ! ReadableStreamDefaultReaderRelease(this).
+    return readable_stream_default_reader_release(*this);
+}
+
+}