Bug 1923505 - Simplify LinkedList -> nsTArray conversion. r=xpcom-reviewers,hiro,nika

Add a ToTArray version that works with LinkedList.

This is much like what we do for other containers, but without walking the list
twice.

Differential Revision: https://phabricator.services.mozilla.com/D225001

dom/animation/AnimationTimeline.cpp

@@ -40,17 +40,18 @@ AnimationTimeline::~AnimationTimeline() { mAnimationOrder.clear(); }
 bool AnimationTimeline::Tick(TickState& aState) {
   bool needsTicks = false;
 
-  AutoTArray<RefPtr<Animation>, 32> animationsToTick;
+#ifdef DEBUG
   for (Animation* animation : mAnimationOrder) {
     MOZ_ASSERT(mAnimations.Contains(animation),
                "The sampling order list should be a subset of the hashset");
     MOZ_ASSERT(!animation->IsHiddenByContentVisibility(),
                "The sampling order list should not contain any animations "
                "that are hidden by content-visibility");
-    animationsToTick.AppendElement(animation);
   }
+#endif
 
-  for (Animation* animation : animationsToTick) {
+  for (Animation* animation :
+       ToTArray<AutoTArray<RefPtr<Animation>, 32>>(mAnimationOrder)) {
     // Skip any animations that are longer need associated with this timeline.
     if (animation->GetTimeline() != this) {
       RemoveAnimation(animation);

dom/animation/DocumentTimeline.cpp

@@ -160,12 +160,8 @@ void DocumentTimeline::NotifyAnimationUpdated(Animation& aAnimation) {
 }
 
 void DocumentTimeline::TriggerAllPendingAnimationsNow() {
-  AutoTArray<RefPtr<Animation>, 32> animationsToTrigger;
-  for (Animation* animation : mAnimationOrder) {
-    animationsToTrigger.AppendElement(animation);
-  }
-
-  for (Animation* animation : animationsToTrigger) {
+  for (Animation* animation :
+       ToTArray<AutoTArray<RefPtr<Animation>, 32>>(mAnimationOrder)) {
     animation->TryTriggerNow();
   }
 }

layout/base/nsRefreshDriver.cpp

@@ -2311,15 +2311,10 @@ void nsRefreshDriver::DetermineProximityToViewportAndNotifyResizeObservers() {
 }
 
 static CallState UpdateAndReduceAnimations(Document& aDocument) {
-  {
-    AutoTArray<RefPtr<DocumentTimeline>, 32> timelinesToTick;
-    for (DocumentTimeline* timeline : aDocument.Timelines()) {
-      timelinesToTick.AppendElement(timeline);
-    }
-
-    for (DocumentTimeline* tl : timelinesToTick) {
-      tl->WillRefresh();
-    }
+  for (DocumentTimeline* tl :
+       ToTArray<AutoTArray<RefPtr<DocumentTimeline>, 32>>(
+           aDocument.Timelines())) {
+    tl->WillRefresh();
   }
 
   if (nsPresContext* pc = aDocument.GetPresContext()) {

mfbt/LinkedList.h

@@ -409,13 +409,13 @@ class LinkedListElement {
 template <typename T>
 class LinkedList {
  private:
-  typedef typename detail::LinkedListElementTraits<T> Traits;
-  typedef typename Traits::RawType RawType;
-  typedef typename Traits::ConstRawType ConstRawType;
-  typedef typename Traits::ClientType ClientType;
-  typedef typename Traits::ConstClientType ConstClientType;
-  typedef LinkedListElement<T>* ElementType;
-  typedef const LinkedListElement<T>* ConstElementType;
+  using Traits = typename detail::LinkedListElementTraits<T>;
+  using RawType = typename Traits::RawType;
+  using ConstRawType = typename Traits::ConstRawType;
+  using ClientType = typename Traits::ClientType;
+  using ConstClientType = typename Traits::ConstClientType;
+  using ElementType = LinkedListElement<T>*;
+  using ConstElementType = const LinkedListElement<T>*;
 
   LinkedListElement<T> sentinel;
 
@@ -445,6 +445,9 @@ class LinkedList {
     }
   };
 
+  using const_iterator = Iterator<ConstRawType, ConstElementType>;
+  using iterator = Iterator<RawType, ElementType>;
+
   LinkedList() : sentinel(LinkedListElement<T>::NodeKind::Sentinel) {}
 
   LinkedList(LinkedList<T>&& aOther) : sentinel(std::move(aOther.sentinel)) {}
@@ -701,6 +704,11 @@ class LinkedList {
   LinkedList(const LinkedList<T>& aOther) = delete;
 };
 
+template <typename T>
+size_t RangeSizeEstimate(const LinkedList<T>&) {
+  return 0;
+}
+
 template <typename T>
 inline void ImplCycleCollectionUnlink(LinkedList<RefPtr<T>>& aField) {
   aField.clear();

toolkit/components/extensions/MatchPattern.cpp

@@ -30,7 +30,9 @@ template <typename Range, typename AsAtom>
 static AtomSet::ArrayType AtomSetFromRange(Range&& aRange,
                                            AsAtom&& aTransform) {
   AtomSet::ArrayType atoms;
-  atoms.SetCapacity(RangeSize(aRange));
+  if (auto estimate = RangeSizeEstimate(aRange)) {
+    atoms.SetCapacity(estimate);
+  }
   std::transform(aRange.begin(), aRange.end(), MakeBackInserter(atoms),
                  std::forward<AsAtom>(aTransform));
 

xpcom/ds/nsBaseHashtable.h

@@ -175,7 +175,8 @@ class nsBaseHashtableValueRange {
 };
 
 template <typename EntryType>
-auto RangeSize(const detail::nsBaseHashtableValueRange<EntryType>& aRange) {
+size_t RangeSizeEstimate(
+    const detail::nsBaseHashtableValueRange<EntryType>& aRange) {
   return aRange.Count();
 }
 

xpcom/ds/nsTArray.h

@@ -3274,11 +3274,14 @@ class nsTArrayView {
   const Span<element_type> mSpan;
 };
 
-template <typename Range, typename = std::enable_if_t<std::is_same_v<
-                              typename std::iterator_traits<
-                                  typename Range::iterator>::iterator_category,
-                              std::random_access_iterator_tag>>>
-auto RangeSize(const Range& aRange) {
+// NOTE(emilio): If changing the name of this or so, make sure to change
+// specializations too.
+template <typename Range,
+          typename = std::enable_if_t<std::is_same_v<
+              typename std::iterator_traits<typename std::remove_reference_t<
+                  Range>::iterator>::iterator_category,
+              std::random_access_iterator_tag>>>
+size_t RangeSizeEstimate(const Range& aRange) {
   // See https://en.cppreference.com/w/cpp/iterator/begin, section 'User-defined
   // overloads'.
   using std::begin;
@@ -3293,12 +3296,14 @@ auto RangeSize(const Range& aRange) {
  * convertible from the range's value type.
  */
 template <typename Array, typename Range>
-auto ToTArray(const Range& aRange) {
+auto ToTArray(Range&& aRange) {
   using std::begin;
   using std::end;
 
   Array res;
-  res.SetCapacity(RangeSize(aRange));
+  if (auto estimate = RangeSizeEstimate(aRange)) {
+    res.SetCapacity(estimate);
+  }
   std::copy(begin(aRange), end(aRange), MakeBackInserter(res));
   return res;
 }
@@ -3307,21 +3312,22 @@ auto ToTArray(const Range& aRange) {
  * Materialize a range as a nsTArray of its (decayed) value type.
  */
 template <typename Range>
-auto ToArray(const Range& aRange) {
-  return ToTArray<nsTArray<std::decay_t<
-      typename std::iterator_traits<typename Range::iterator>::value_type>>>(
-      aRange);
+auto ToArray(Range&& aRange) {
+  return ToTArray<nsTArray<std::decay_t<typename std::iterator_traits<
+      typename std::remove_reference_t<Range>::iterator>::value_type>>>(
+      std::forward<Range>(aRange));
 }
 
 /**
  * Appends all elements from a range to an array.
  */
 template <typename Array, typename Range>
-void AppendToArray(Array& aArray, const Range& aRange) {
+void AppendToArray(Array& aArray, Range&& aRange) {
   using std::begin;
   using std::end;
-
-  aArray.SetCapacity(aArray.Length() + RangeSize(aRange));
+  if (auto estimate = RangeSizeEstimate(aRange)) {
+    aArray.SetCapacity(aArray.Length() + estimate);
+  }
   std::copy(begin(aRange), end(aRange), MakeBackInserter(aArray));
 }
 

xpcom/ds/nsTHashSet.h

@@ -134,7 +134,7 @@ class nsTBaseHashSet : protected nsTHashtable<KeyClass> {
 };
 
 template <typename KeyClass>
-auto RangeSize(const nsTBaseHashSet<KeyClass>& aRange) {
+size_t RangeSizeEstimate(const nsTBaseHashSet<KeyClass>& aRange) {
   return aRange.Count();
 }
 

xpcom/ds/nsTHashtable.h

@@ -168,7 +168,8 @@ class nsTHashtableKeyRange {
 };
 
 template <typename EntryType>
-auto RangeSize(const ::detail::nsTHashtableKeyRange<EntryType>& aRange) {
+size_t RangeSizeEstimate(
+    const ::detail::nsTHashtableKeyRange<EntryType>& aRange) {
   return aRange.Count();
 }