1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7 #ifndef mozilla_dom_QueueWithSizes_h
8 #define mozilla_dom_QueueWithSizes_h
11 #include "js/TypeDecls.h"
13 #include "mozilla/ErrorResult.h"
14 #include "mozilla/UniquePtr.h"
17 namespace mozilla::dom
{
19 // Note: Consumers of QueueWithSize need to ensure it is traced. See
20 // ReadableStreamDefaultController.cpp for an example.
22 struct ValueWithSize
: LinkedListElement
<ValueWithSize
> {
23 ValueWithSize(JS::Handle
<JS::Value
> aValue
, double aSize
)
24 : mValue(aValue
), mSize(aSize
){};
26 JS::Heap
<JS::Value
> mValue
;
30 // This type is a little tricky lifetime wise: Despite the fact that we're
31 // talking about linked list of VaueWithSize, what is actually stored in the
32 // list are dynamically allocated ValueWithSize*. As a result, these have to be
33 // deleted. There are two ways this lifetime is managed:
35 // 1. In DequeueValue we pop the first element into a UniquePtr, so that it is
36 // correctly cleaned up at destruction time.
37 // 2. We use an AutoCleanLinkedList which will delete elements when destroyed
39 using QueueWithSizes
= AutoCleanLinkedList
<ValueWithSize
>;
41 // https://streams.spec.whatwg.org/#is-non-negative-number
42 inline bool IsNonNegativeNumber(double v
) {
53 // https://streams.spec.whatwg.org/#enqueue-value-with-size
54 template <class QueueContainingClass
>
55 inline void EnqueueValueWithSize(QueueContainingClass aContainer
,
56 JS::Handle
<JS::Value
> aValue
, double aSize
,
58 // Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
59 // slots. (Implicit by template instantiation.)
60 // Step 2. If ! IsNonNegativeNumber(size) is false, throw a RangeError
62 if (!IsNonNegativeNumber(aSize
)) {
63 aRv
.ThrowRangeError("invalid size");
67 // Step 3. If size is +∞, throw a RangeError exception.
68 if (std::isinf(aSize
)) {
69 aRv
.ThrowRangeError("Infinite queue size");
73 // Step 4. Append a new value-with-size with value value and size size to
74 // container.[[queue]].
75 // (See the comment on QueueWithSizes for the lifetime reasoning around this
77 ValueWithSize
* valueWithSize
= new ValueWithSize(aValue
, aSize
);
78 aContainer
->Queue().insertBack(valueWithSize
);
79 // Step 5. Set container.[[queueTotalSize]] to container.[[queueTotalSize]] +
81 aContainer
->SetQueueTotalSize(aContainer
->QueueTotalSize() + aSize
);
84 // https://streams.spec.whatwg.org/#dequeue-value
85 template <class QueueContainingClass
>
86 inline void DequeueValue(QueueContainingClass aContainer
,
87 JS::MutableHandle
<JS::Value
> aResultValue
) {
88 // Step 1. Implicit via template instantiation.
90 MOZ_ASSERT(!aContainer
->Queue().isEmpty());
93 // UniquePtr to ensure memory is freed.
94 UniquePtr
<ValueWithSize
> valueWithSize(aContainer
->Queue().popFirst());
97 aContainer
->SetQueueTotalSize(aContainer
->QueueTotalSize() -
98 valueWithSize
->mSize
);
101 if (aContainer
->QueueTotalSize() < 0) {
102 aContainer
->SetQueueTotalSize(0);
106 aResultValue
.set(valueWithSize
->mValue
);
109 // https://streams.spec.whatwg.org/#peek-queue-value
110 template <class QueueContainingClass
>
111 inline void PeekQueueValue(QueueContainingClass aContainer
,
112 JS::MutableHandle
<JS::Value
> aResultValue
) {
113 // Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
115 // Step 2. Assert: container.[[queue]] is not empty.
116 MOZ_ASSERT(!aContainer
->Queue().isEmpty());
118 // Step 3. Let valueWithSize be container.[[queue]][0].
119 ValueWithSize
* valueWithSize
= aContainer
->Queue().getFirst();
121 // Step 4. Return valueWithSize’s value.
122 aResultValue
.set(valueWithSize
->mValue
);
125 // https://streams.spec.whatwg.org/#reset-queue
126 template <class QueueContainingClass
>
127 inline void ResetQueue(QueueContainingClass aContainer
) {
128 // Step 1. Assert: container has [[queue]] and [[queueTotalSize]] internal
131 // Step 2. Set container.[[queue]] to a new empty list.
132 aContainer
->Queue().clear();
134 // Step 3. Set container.[[queueTotalSize]] to 0.
135 aContainer
->SetQueueTotalSize(0.0);
138 } // namespace mozilla::dom