1 files changed, 151 insertions, 0 deletions
diff --git a/dom/workers/Queue.h b/dom/workers/Queue.h
new file mode 100644
index 0000000000..cf65932698
--- /dev/null
+++ b/dom/workers/Queue.h
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_workerinternal_Queue_h
+#define mozilla_dom_workerinternal_Queue_h
+
+#include "mozilla/Mutex.h"
+#include "nsTArray.h"
+
+namespace mozilla::dom::workerinternals {
+
+template <typename T, int TCount>
+struct StorageWithTArray {
+  typedef AutoTArray<T, TCount> StorageType;
+
+  static void Reverse(StorageType& aStorage) {
+    uint32_t length = aStorage.Length();
+    for (uint32_t index = 0; index < length / 2; index++) {
+      uint32_t reverseIndex = length - 1 - index;
+
+      T t1 = aStorage.ElementAt(index);
+      T t2 = aStorage.ElementAt(reverseIndex);
+
+      aStorage.ReplaceElementsAt(index, 1, t2);
+      aStorage.ReplaceElementsAt(reverseIndex, 1, t1);
+    }
+  }
+
+  static bool IsEmpty(const StorageType& aStorage) {
+    return !!aStorage.IsEmpty();
+  }
+
+  static void Push(StorageType& aStorage, const T& aEntry) {
+    aStorage.AppendElement(aEntry);
+  }
+
+  static bool Pop(StorageType& aStorage, T& aEntry) {
+    if (IsEmpty(aStorage)) {
+      return false;
+    }
+
+    aEntry = aStorage.PopLastElement();
+    return true;
+  }
+
+  static void Clear(StorageType& aStorage) { aStorage.Clear(); }
+
+  static void Compact(StorageType& aStorage) { aStorage.Compact(); }
+};
+
+class MOZ_CAPABILITY("mutex") LockingWithMutex {
+  mozilla::Mutex mMutex;
+
+ protected:
+  LockingWithMutex() : mMutex("LockingWithMutex::mMutex") {}
+
+  void Lock() MOZ_CAPABILITY_ACQUIRE() { mMutex.Lock(); }
+
+  void Unlock() MOZ_CAPABILITY_RELEASE() { mMutex.Unlock(); }
+
+  class MOZ_SCOPED_CAPABILITY AutoLock {
+    LockingWithMutex& mHost;
+
+   public:
+    explicit AutoLock(LockingWithMutex& aHost) MOZ_CAPABILITY_ACQUIRE(aHost)
+        : mHost(aHost) {
+      mHost.Lock();
+    }
+
+    ~AutoLock() MOZ_CAPABILITY_RELEASE() { mHost.Unlock(); }
+  };
+
+  friend class AutoLock;
+};
+
+class NoLocking {
+ protected:
+  void Lock() {}
+
+  void Unlock() {}
+
+  class AutoLock {
+   public:
+    explicit AutoLock(NoLocking& aHost) {}
+
+    ~AutoLock() = default;
+  };
+};
+
+template <typename T, int TCount = 256, class LockingPolicy = NoLocking,
+          class StoragePolicy =
+              StorageWithTArray<T, TCount % 2 ? TCount / 2 + 1 : TCount / 2> >
+class Queue : public LockingPolicy {
+  typedef typename StoragePolicy::StorageType StorageType;
+  typedef typename LockingPolicy::AutoLock AutoLock;
+
+  StorageType mStorage1;
+  StorageType mStorage2;
+
+  StorageType* mFront;
+  StorageType* mBack;
+
+ public:
+  Queue() : mFront(&mStorage1), mBack(&mStorage2) {}
+
+  bool IsEmpty() {
+    AutoLock lock(*this);
+    return StoragePolicy::IsEmpty(*mFront) && StoragePolicy::IsEmpty(*mBack);
+  }
+
+  void Push(const T& aEntry) {
+    AutoLock lock(*this);
+    StoragePolicy::Push(*mBack, aEntry);
+  }
+
+  bool Pop(T& aEntry) {
+    AutoLock lock(*this);
+    if (StoragePolicy::IsEmpty(*mFront)) {
+      StoragePolicy::Compact(*mFront);
+      StoragePolicy::Reverse(*mBack);
+      StorageType* tmp = mFront;
+      mFront = mBack;
+      mBack = tmp;
+    }
+    return StoragePolicy::Pop(*mFront, aEntry);
+  }
+
+  void Clear() {
+    AutoLock lock(*this);
+    StoragePolicy::Clear(*mFront);
+    StoragePolicy::Clear(*mBack);
+  }
+
+  // XXX Do we need this?
+  void Lock() { LockingPolicy::Lock(); }
+
+  // XXX Do we need this?
+  void Unlock() { LockingPolicy::Unlock(); }
+
+ private:
+  // Queue is not copyable.
+  Queue(const Queue&);
+  Queue& operator=(const Queue&);
+};
+
+}  // namespace mozilla::dom::workerinternals
+
+#endif /* mozilla_dom_workerinternals_Queue_h*/