import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

dom/workers/Queue.h

@@ -0,0 +1,203 @@
+/* -*- 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_workers_queue_h__
+#define mozilla_dom_workers_queue_h__
+
+#include "Workers.h"
+
+#include "mozilla/Mutex.h"
+#include "nsTArray.h"
+
+BEGIN_WORKERS_NAMESPACE
+
+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 bool Push(StorageType& aStorage, const T& aEntry)
+  {
+    return !!aStorage.AppendElement(aEntry);
+  }
+
+  static bool Pop(StorageType& aStorage, T& aEntry)
+  {
+    if (IsEmpty(aStorage)) {
+      return false;
+    }
+
+    uint32_t index = aStorage.Length() - 1;
+    aEntry = aStorage.ElementAt(index);
+    aStorage.RemoveElementAt(index);
+    return true;
+  }
+
+  static void Clear(StorageType& aStorage)
+  {
+    aStorage.Clear();
+  }
+
+  static void Compact(StorageType& aStorage)
+  {
+    aStorage.Compact();
+  }
+};
+
+class LockingWithMutex
+{
+  mozilla::Mutex mMutex;
+
+protected:
+  LockingWithMutex()
+  : mMutex("LockingWithMutex::mMutex")
+  { }
+
+  void Lock()
+  {
+    mMutex.Lock();
+  }
+
+  void Unlock()
+  {
+    mMutex.Unlock();
+  }
+
+  class AutoLock
+  {
+    LockingWithMutex& mHost;
+
+  public:
+    explicit AutoLock(LockingWithMutex& aHost)
+    : mHost(aHost)
+    {
+      mHost.Lock();
+    }
+
+    ~AutoLock()
+    {
+      mHost.Unlock();
+    }
+  };
+
+  friend class AutoLock;
+};
+
+class NoLocking
+{
+protected:
+  void Lock()
+  { }
+
+  void Unlock()
+  { }
+
+  class AutoLock
+  {
+  public:
+    explicit AutoLock(NoLocking& aHost)
+    { }
+
+    ~AutoLock()
+    { }
+  };
+};
+
+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);
+  }
+
+  bool Push(const T& aEntry)
+  {
+    AutoLock lock(*this);
+    return 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&);
+};
+
+END_WORKERS_NAMESPACE
+
+#endif /* mozilla_dom_workers_queue_h__ */