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      1 /*
      2  * Copyright (C) 2013 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer
     12  *    in the documentation and/or other materials provided with the
     13  *    distribution.
     14  * 3. Neither the name of Google Inc. nor the names of its contributors
     15  *    may be used to endorse or promote products derived from this
     16  *    software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef CustomElementCallbackDispatcher_h
     32 #define CustomElementCallbackDispatcher_h
     33 
     34 #include "core/dom/custom/CustomElementCallbackQueue.h"
     35 #include "wtf/Vector.h"
     36 
     37 namespace WebCore {
     38 
     39 class CustomElementScheduler;
     40 
     41 // FIXME: Rename this CustomElementProcessingStack. It only handles
     42 // the processing stack.
     43 class CustomElementCallbackDispatcher {
     44     WTF_MAKE_NONCOPYABLE(CustomElementCallbackDispatcher);
     45 public:
     46     // This is stack allocated in many DOM callbacks. Make it cheap.
     47     class CallbackDeliveryScope {
     48     public:
     49         CallbackDeliveryScope()
     50             : m_savedElementQueueStart(s_elementQueueStart)
     51         {
     52             s_elementQueueStart = s_elementQueueEnd;
     53         }
     54 
     55         ~CallbackDeliveryScope()
     56         {
     57             if (s_elementQueueStart != s_elementQueueEnd)
     58                 processElementQueueAndPop();
     59             s_elementQueueStart = m_savedElementQueueStart;
     60         }
     61 
     62     private:
     63         size_t m_savedElementQueueStart;
     64     };
     65 
     66     static bool inCallbackDeliveryScope() { return s_elementQueueStart; }
     67 
     68 protected:
     69     friend class CustomElementScheduler;
     70     static CustomElementCallbackDispatcher& instance();
     71     void enqueue(CustomElementCallbackQueue*);
     72 
     73 private:
     74     CustomElementCallbackDispatcher()
     75     {
     76         // Add a null element as a sentinel. This makes it possible to
     77         // identify elements queued when there is no
     78         // CallbackDeliveryScope active. Also, if the processing stack
     79         // is popped when empty, this sentinel will cause a null deref
     80         // crash.
     81         CustomElementCallbackQueue* sentinel = 0;
     82         for (size_t i = 0; i < kNumSentinels; i++)
     83             m_flattenedProcessingStack.append(sentinel);
     84         ASSERT(s_elementQueueEnd == m_flattenedProcessingStack.size());
     85     }
     86 
     87     // The start of the element queue on the top of the processing
     88     // stack. An offset into instance().m_flattenedProcessingStack.
     89     static size_t s_elementQueueStart;
     90 
     91     // The end of the element queue on the top of the processing
     92     // stack. A cache of instance().m_flattenedProcessingStack.size().
     93     static size_t s_elementQueueEnd;
     94 
     95     static CustomElementCallbackQueue::ElementQueueId currentElementQueue() { return CustomElementCallbackQueue::ElementQueueId(s_elementQueueStart); }
     96 
     97     static void processElementQueueAndPop();
     98     void processElementQueueAndPop(size_t start, size_t end);
     99 
    100     // The processing stack, flattened. Element queues lower in the
    101     // stack appear toward the head of the vector. The first element
    102     // is a null sentinel value.
    103     static const size_t kNumSentinels = 1;
    104     Vector<CustomElementCallbackQueue*> m_flattenedProcessingStack;
    105 };
    106 
    107 }
    108 
    109 #endif // CustomElementCallbackDispatcher_h
    110