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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/CustomElementCallbackQueue.h"
     35 #include "core/dom/Element.h"
     36 #include "wtf/HashMap.h"
     37 #include "wtf/OwnPtr.h"
     38 #include "wtf/PassRefPtr.h"
     39 #include "wtf/Vector.h"
     40 
     41 namespace WebCore {
     42 
     43 class CustomElementCallbackDispatcher {
     44     WTF_MAKE_NONCOPYABLE(CustomElementCallbackDispatcher);
     45 public:
     46     static CustomElementCallbackDispatcher& instance();
     47 
     48     // This is stack allocated in many DOM callbacks. Make it cheap.
     49     class CallbackDeliveryScope {
     50     public:
     51         CallbackDeliveryScope()
     52             : m_savedElementQueueStart(s_elementQueueStart)
     53         {
     54             s_elementQueueStart = s_elementQueueEnd;
     55         }
     56 
     57         ~CallbackDeliveryScope()
     58         {
     59             if (s_elementQueueStart != s_elementQueueEnd)
     60                 processElementQueueAndPop();
     61             s_elementQueueStart = m_savedElementQueueStart;
     62         }
     63 
     64     private:
     65         size_t m_savedElementQueueStart;
     66     };
     67 
     68     // Returns true if more work may have to be performed at the
     69     // checkpoint by this or other workers (for example, this work
     70     // invoked author scripts)
     71     bool dispatch();
     72 
     73 protected:
     74     friend class CustomElementCallbackScheduler;
     75 
     76     CustomElementCallbackQueue* createAtFrontOfCurrentElementQueue(PassRefPtr<Element>);
     77     CustomElementCallbackQueue* ensureInCurrentElementQueue(PassRefPtr<Element>);
     78 
     79 private:
     80     CustomElementCallbackDispatcher()
     81     {
     82         // Add a null element as a sentinel. This makes it possible to
     83         // identify elements queued when there is no
     84         // CallbackDeliveryScope active. Also, if the processing stack
     85         // is popped when empty, this sentinel will cause a null deref
     86         // crash.
     87         CustomElementCallbackQueue* sentinel = 0;
     88         for (size_t i = 0; i < kNumSentinels; i++)
     89             m_flattenedProcessingStack.append(sentinel);
     90         ASSERT(s_elementQueueEnd == m_flattenedProcessingStack.size());
     91     }
     92 
     93     // The start of the element queue on the top of the processing
     94     // stack. An offset into instance().m_flattenedProcessingStack.
     95     static size_t s_elementQueueStart;
     96 
     97     // The end of the element queue on the top of the processing
     98     // stack. A cache of instance().m_flattenedProcessingStack.size().
     99     static size_t s_elementQueueEnd;
    100 
    101     static bool inCallbackDeliveryScope() { return s_elementQueueStart; }
    102 
    103     typedef int ElementQueue;
    104     static ElementQueue currentElementQueue() { return ElementQueue(s_elementQueueStart); }
    105 
    106     static void processElementQueueAndPop();
    107     void processElementQueueAndPop(size_t start, size_t end);
    108 
    109     CustomElementCallbackQueue* createCallbackQueue(PassRefPtr<Element>);
    110     CustomElementCallbackQueue* ensureCallbackQueue(PassRefPtr<Element>);
    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     typedef HashMap<Element*, OwnPtr<CustomElementCallbackQueue> > ElementCallbackQueueMap;
    119     ElementCallbackQueueMap m_elementCallbackQueueMap;
    120 };
    121 
    122 }
    123 
    124 #endif // CustomElementCallbackDispatcher_h
    125