LibWeb: Add the stream queue-related abstract operations

Userland/Libraries/LibWeb/Streams/AbstractOperations.h

@@ -9,6 +9,7 @@
 
 #include <LibJS/Heap/GCPtr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/Streams/QueueOperations.h>
 #include <LibWeb/WebIDL/Promise.h>
 
 namespace Web::Streams {

Userland/Libraries/LibWeb/Streams/QueueOperations.h

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Error.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+
+namespace Web::Streams {
+
+// https://streams.spec.whatwg.org/#value-with-size
+struct ValueWithSize {
+    JS::Value value;
+    double size;
+};
+
+// https://streams.spec.whatwg.org/#dequeue-value
+template<typename T>
+JS::Value dequeue_value(T& container)
+{
+    // 1. Assert: container has [[queue]] and [[queueTotalSize]] internal slots.
+
+    // 2. Assert: container.[[queue]] is not empty.
+    VERIFY(!container.queue().is_empty());
+
+    // 3. Let valueWithSize be container.[[queue]][0].
+    // 4. Remove valueWithSize from container.[[queue]].
+    auto value_with_size = container.queue().take_first();
+
+    // 5. Set container.[[queueTotalSize]] to container.[[queueTotalSize]] − valueWithSize’s size.
+    container.set_queue_total_size(container.queue_total_size() - value_with_size.size);
+
+    // 6. If container.[[queueTotalSize]] < 0, set container.[[queueTotalSize]] to 0. (This can occur due to rounding errors.)
+    if (container.queue_total_size() < 0.0)
+        container.set_queue_total_size(0.0);
+
+    // 7. Return valueWithSize’s value.
+    return value_with_size.value;
+}
+
+// https://streams.spec.whatwg.org/#enqueue-value-with-size
+template<typename T>
+WebIDL::ExceptionOr<void> enqueue_value_with_size(T& container, JS::Value value, double size)
+{
+    // 1. Assert: container has [[queue]] and [[queueTotalSize]] internal slots.
+
+    // 2. If ! IsNonNegativeNumber(size) is false, throw a RangeError exception.
+    if (size < 0.0)
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::RangeError, "Chunk has negative size"sv };
+
+    // 3. If size is +∞, throw a RangeError exception.
+    if (size == HUGE_VAL)
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::RangeError, "Chunk has infinite size"sv };
+
+    // 4. Append a new value-with-size with value value and size size to container.[[queue]].
+    container.queue().append({ value, size });
+
+    // 5. Set container.[[queueTotalSize]] to container.[[queueTotalSize]] + size.
+    container.set_queue_total_size(container.queue_total_size() + size);
+
+    return {};
+}
+
+// https://streams.spec.whatwg.org/#peek-queue-value
+template<typename T>
+JS::Value peek_queue_value(T& container)
+{
+    // 1. Assert: container has [[queue]] and [[queueTotalSize]] internal slots.
+
+    // 2. Assert: container.[[queue]] is not empty.
+    VERIFY(!container.queue().is_empty());
+
+    // 3. Let valueWithSize be container.[[queue]][0].
+    auto& value_with_size = container.queue().first();
+
+    // 4. Return valueWithSize’s value.
+    return value_with_size.value;
+}
+
+// https://streams.spec.whatwg.org/#reset-queue
+template<typename T>
+void reset_queue(T& container)
+{
+    // 1. Assert: container has [[queue]] and [[queueTotalSize]] internal slots.
+
+    // 2. Set container.[[queue]] to a new empty list.
+    container.queue().clear();
+
+    // 3. Set container.[[queueTotalSize]] to 0.
+    container.set_queue_total_size(0);
+}
+
+}