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140 lines
4.7 KiB
C++
140 lines
4.7 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_dom_QueueWithSizes_h
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#define mozilla_dom_QueueWithSizes_h
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#include <cmath>
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#include "js/TypeDecls.h"
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#include "js/Value.h"
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#include "mozilla/ErrorResult.h"
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#include "mozilla/UniquePtr.h"
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#include "nsTArray.h"
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namespace mozilla::dom {
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// Note: Consumers of QueueWithSize need to ensure it is traced. See
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// ReadableStreamDefaultController.cpp for an example.
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struct ValueWithSize : LinkedListElement<ValueWithSize> {
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ValueWithSize(JS::Handle<JS::Value> aValue, double aSize)
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: mValue(aValue), mSize(aSize){};
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JS::Heap<JS::Value> mValue;
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double mSize = 0.0f;
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};
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// This type is a little tricky lifetime wise: Despite the fact that we're
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// talking about linked list of VaueWithSize, what is actually stored in the
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// list are dynamically allocated ValueWithSize*. As a result, these have to be
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// deleted. There are two ways this lifetime is managed:
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//
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// 1. In DequeueValue we pop the first element into a UniquePtr, so that it is
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// correctly cleaned up at destruction time.
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// 2. We use an AutoCleanLinkedList which will delete elements when destroyed
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// or `clear`ed.
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using QueueWithSizes = AutoCleanLinkedList<ValueWithSize>;
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// https://streams.spec.whatwg.org/#is-non-negative-number
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inline bool IsNonNegativeNumber(double v) {
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// Step 1. Implicit.
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// Step 2.
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if (std::isnan(v)) {
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return false;
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}
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// Step 3.
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return !(v < 0);
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}
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// https://streams.spec.whatwg.org/#enqueue-value-with-size
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template <class QueueContainingClass>
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inline void EnqueueValueWithSize(QueueContainingClass aContainer,
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JS::Handle<JS::Value> aValue, double aSize,
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ErrorResult& aRv) {
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// Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
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// slots. (Implicit by template instantiation.)
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// Step 2. If ! IsNonNegativeNumber(size) is false, throw a RangeError
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// exception.
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if (!IsNonNegativeNumber(aSize)) {
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aRv.ThrowRangeError("invalid size");
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return;
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}
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// Step 3. If size is +∞, throw a RangeError exception.
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if (std::isinf(aSize)) {
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aRv.ThrowRangeError("Infinite queue size");
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return;
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}
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// Step 4. Append a new value-with-size with value value and size size to
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// container.[[queue]].
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// (See the comment on QueueWithSizes for the lifetime reasoning around this
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// allocation.)
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ValueWithSize* valueWithSize = new ValueWithSize(aValue, aSize);
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aContainer->Queue().insertBack(valueWithSize);
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// Step 5. Set container.[[queueTotalSize]] to container.[[queueTotalSize]] +
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// size.
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aContainer->SetQueueTotalSize(aContainer->QueueTotalSize() + aSize);
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}
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// https://streams.spec.whatwg.org/#dequeue-value
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template <class QueueContainingClass>
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inline void DequeueValue(QueueContainingClass aContainer,
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JS::MutableHandle<JS::Value> aResultValue) {
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// Step 1. Implicit via template instantiation.
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// Step 2.
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MOZ_ASSERT(!aContainer->Queue().isEmpty());
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// Step 3+4
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// UniquePtr to ensure memory is freed.
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UniquePtr<ValueWithSize> valueWithSize(aContainer->Queue().popFirst());
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// Step 5.
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aContainer->SetQueueTotalSize(aContainer->QueueTotalSize() -
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valueWithSize->mSize);
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// Step 6.
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if (aContainer->QueueTotalSize() < 0) {
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aContainer->SetQueueTotalSize(0);
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}
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// Step 7.
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aResultValue.set(valueWithSize->mValue);
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}
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// https://streams.spec.whatwg.org/#peek-queue-value
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template <class QueueContainingClass>
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inline void PeekQueueValue(QueueContainingClass aContainer,
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JS::MutableHandle<JS::Value> aResultValue) {
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// Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
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// slots.
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// Step 2. Assert: container.[[queue]] is not empty.
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MOZ_ASSERT(!aContainer->Queue().isEmpty());
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// Step 3. Let valueWithSize be container.[[queue]][0].
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ValueWithSize* valueWithSize = aContainer->Queue().getFirst();
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// Step 4. Return valueWithSize’s value.
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aResultValue.set(valueWithSize->mValue);
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}
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// https://streams.spec.whatwg.org/#reset-queue
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template <class QueueContainingClass>
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inline void ResetQueue(QueueContainingClass aContainer) {
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// Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
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// slots. (implicit)
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// Step 2. Set container.[[queue]] to a new empty list.
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aContainer->Queue().clear();
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// Step 3. Set container.[[queueTotalSize]] to 0.
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aContainer->SetQueueTotalSize(0.0);
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}
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} // namespace mozilla::dom
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#endif
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