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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/CustomElementBaseElementQueue.h"
     35 #include "wtf/Vector.h"
     36 
     37 namespace WebCore {
     38 
     39 class CustomElementCallbackQueue;
     40 class CustomElementCallbackScheduler;
     41 
     42 class CustomElementCallbackDispatcher {
     43     WTF_MAKE_NONCOPYABLE(CustomElementCallbackDispatcher);
     44 public:
     45     static CustomElementCallbackDispatcher& instance();
     46 
     47     // This is stack allocated in many DOM callbacks. Make it cheap.
     48     class CallbackDeliveryScope {
     49     public:
     50         CallbackDeliveryScope()
     51             : m_savedElementQueueStart(s_elementQueueStart)
     52         {
     53             s_elementQueueStart = s_elementQueueEnd;
     54         }
     55 
     56         ~CallbackDeliveryScope()
     57         {
     58             if (s_elementQueueStart != s_elementQueueEnd)
     59                 processElementQueueAndPop();
     60             s_elementQueueStart = m_savedElementQueueStart;
     61         }
     62 
     63     private:
     64         size_t m_savedElementQueueStart;
     65     };
     66 
     67     // Returns true if more work may have to be performed at the
     68     // checkpoint by this or other workers (for example, this work
     69     // invoked author scripts)
     70     bool dispatch();
     71 
     72 protected:
     73     friend class CustomElementCallbackScheduler;
     74     void enqueue(CustomElementCallbackQueue*);
     75 
     76 private:
     77     CustomElementCallbackDispatcher()
     78     {
     79         // Add a null element as a sentinel. This makes it possible to
     80         // identify elements queued when there is no
     81         // CallbackDeliveryScope active. Also, if the processing stack
     82         // is popped when empty, this sentinel will cause a null deref
     83         // crash.
     84         CustomElementCallbackQueue* sentinel = 0;
     85         for (size_t i = 0; i < kNumSentinels; i++)
     86             m_flattenedProcessingStack.append(sentinel);
     87         ASSERT(s_elementQueueEnd == m_flattenedProcessingStack.size());
     88     }
     89 
     90     // The start of the element queue on the top of the processing
     91     // stack. An offset into instance().m_flattenedProcessingStack.
     92     static size_t s_elementQueueStart;
     93 
     94     // The end of the element queue on the top of the processing
     95     // stack. A cache of instance().m_flattenedProcessingStack.size().
     96     static size_t s_elementQueueEnd;
     97 
     98     static bool inCallbackDeliveryScope() { return s_elementQueueStart; }
     99 
    100     typedef int ElementQueue;
    101     static ElementQueue baseElementQueue() { return ElementQueue(0); }
    102     static ElementQueue currentElementQueue() { return ElementQueue(s_elementQueueStart); }
    103 
    104     static void processElementQueueAndPop();
    105     void processElementQueueAndPop(size_t start, size_t end);
    106 
    107     // The base element queue, used when no CallbackDeliveryScope is
    108     // active. Callbacks for elements created by the parser are
    109     // enqueued here.
    110     CustomElementBaseElementQueue m_baseElementQueue;
    111 
    112     // The processing stack, flattened. Element queues lower in the
    113     // stack appear toward the head of the vector. The first element
    114     // is a null sentinel value.
    115     static const size_t kNumSentinels = 1;
    116     Vector<CustomElementCallbackQueue*> m_flattenedProcessingStack;
    117 };
    118 
    119 }
    120 
    121 #endif // CustomElementCallbackDispatcher_h
    122