The Tor Browser: dom/workers/Queue.h@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */

     2 /* This Source Code Form is subject to the terms of the Mozilla Public

     3  * License, v. 2.0. If a copy of the MPL was not distributed with this

     4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 #ifndef mozilla_dom_workers_queue_h__

     7 #define mozilla_dom_workers_queue_h__

     9 #include "Workers.h"

    11 #include "mozilla/Mutex.h"

    12 #include "nsTArray.h"

    14 BEGIN_WORKERS_NAMESPACE

    16 template <typename T, int TCount>

    17 struct StorageWithTArray

    18 {

    19   typedef nsAutoTArray<T, TCount> StorageType;

    21   static void Reverse(StorageType& aStorage)

    22   {

    23     uint32_t length = aStorage.Length();

    24     for (uint32_t index = 0; index < length / 2; index++) {

    25       uint32_t reverseIndex = length - 1 - index;

    27       T t1 = aStorage.ElementAt(index);

    28       T t2 = aStorage.ElementAt(reverseIndex);

    30       aStorage.ReplaceElementsAt(index, 1, t2);

    31       aStorage.ReplaceElementsAt(reverseIndex, 1, t1);

    32     }

    33   }

    35   static bool IsEmpty(const StorageType& aStorage)

    36   {

    37     return !!aStorage.IsEmpty();

    38   }

    40   static bool Push(StorageType& aStorage, const T& aEntry)

    41   {

    42     return !!aStorage.AppendElement(aEntry);

    43   }

    45   static bool Pop(StorageType& aStorage, T& aEntry)

    46   {

    47     if (IsEmpty(aStorage)) {

    48       return false;

    49     }

    51     uint32_t index = aStorage.Length() - 1;

    52     aEntry = aStorage.ElementAt(index);

    53     aStorage.RemoveElementAt(index);

    54     return true;

    55   }

    57   static void Clear(StorageType& aStorage)

    58   {

    59     aStorage.Clear();

    60   }

    62   static void Compact(StorageType& aStorage)

    63   {

    64     aStorage.Compact();

    65   }

    66 };

    68 class LockingWithMutex

    69 {

    70   mozilla::Mutex mMutex;

    72 protected:

    73   LockingWithMutex()

    74   : mMutex("LockingWithMutex::mMutex")

    75   { }

    77   void Lock()

    78   {

    79     mMutex.Lock();

    80   }

    82   void Unlock()

    83   {

    84     mMutex.Unlock();

    85   }

    87   class AutoLock

    88   {

    89     LockingWithMutex& mHost;

    91   public:

    92     AutoLock(LockingWithMutex& aHost)

    93     : mHost(aHost)

    94     {

    95       mHost.Lock();

    96     }

    98     ~AutoLock()

    99     {

   100       mHost.Unlock();

   101     }

   102   };

   104   friend class AutoLock;

   105 };

   107 class NoLocking

   108 {

   109 protected:

   110   void Lock()

   111   { }

   113   void Unlock()

   114   { }

   116   class AutoLock

   117   {

   118   public:

   119     AutoLock(NoLocking& aHost)

   120     { }

   122     ~AutoLock()

   123     { }

   124   };

   125 };

   127 template <typename T,

   128           int TCount = 256,

   129           class LockingPolicy = NoLocking,

   130           class StoragePolicy = StorageWithTArray<T, TCount % 2 ?

   131                                                      TCount / 2 + 1 :

   132                                                      TCount / 2> >

   133 class Queue : public LockingPolicy

   134 {

   135   typedef typename StoragePolicy::StorageType StorageType;

   136   typedef typename LockingPolicy::AutoLock AutoLock;

   138   StorageType mStorage1;

   139   StorageType mStorage2;

   141   StorageType* mFront;

   142   StorageType* mBack;

   144 public:

   145   Queue()

   146   : mFront(&mStorage1), mBack(&mStorage2)

   147   { }

   149   bool IsEmpty()

   150   {

   151     AutoLock lock(*this);

   152     return StoragePolicy::IsEmpty(*mFront) &&

   153            StoragePolicy::IsEmpty(*mBack);

   154   }

   156   bool Push(const T& aEntry)

   157   {

   158     AutoLock lock(*this);

   159     return StoragePolicy::Push(*mBack, aEntry);

   160   }

   162   bool Pop(T& aEntry)

   163   {

   164     AutoLock lock(*this);

   165     if (StoragePolicy::IsEmpty(*mFront)) {

   166       StoragePolicy::Compact(*mFront);

   167       StoragePolicy::Reverse(*mBack);

   168       StorageType* tmp = mFront;

   169       mFront = mBack;

   170       mBack = tmp;

   171     }

   172     return StoragePolicy::Pop(*mFront, aEntry);

   173   }

   175   void Clear()

   176   {

   177     AutoLock lock(*this);

   178     StoragePolicy::Clear(*mFront);

   179     StoragePolicy::Clear(*mBack);

   180   }

   182   // XXX Do we need this?

   183   void Lock()

   184   {

   185     LockingPolicy::Lock();

   186   }

   188   // XXX Do we need this?

   189   void Unlock()

   190   {

   191     LockingPolicy::Unlock();

   192   }

   194 private:

   195   // Queue is not copyable.

   196   Queue(const Queue&);

   197   Queue & operator=(const Queue&);

   198 };

   200 END_WORKERS_NAMESPACE

   202 #endif /* mozilla_dom_workers_queue_h__ */

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