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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 "wtf/Vector.h" |  | 
| 35 |  | 
| 36 namespace WebCore { |  | 
| 37 |  | 
| 38 class CustomElementCallbackQueue; |  | 
| 39 class CustomElementCallbackScheduler; |  | 
| 40 |  | 
| 41 class CustomElementCallbackDispatcher { |  | 
| 42     WTF_MAKE_NONCOPYABLE(CustomElementCallbackDispatcher); |  | 
| 43 public: |  | 
| 44     static CustomElementCallbackDispatcher& instance(); |  | 
| 45 |  | 
| 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     // Returns true if more work may have to be performed at the |  | 
| 67     // checkpoint by this or other workers (for example, this work |  | 
| 68     // invoked author scripts) |  | 
| 69     bool dispatch(); |  | 
| 70 |  | 
| 71 protected: |  | 
| 72     friend class CustomElementCallbackScheduler; |  | 
| 73     void enqueue(CustomElementCallbackQueue*); |  | 
| 74 |  | 
| 75 private: |  | 
| 76     CustomElementCallbackDispatcher() |  | 
| 77     { |  | 
| 78         // Add a null element as a sentinel. This makes it possible to |  | 
| 79         // identify elements queued when there is no |  | 
| 80         // CallbackDeliveryScope active. Also, if the processing stack |  | 
| 81         // is popped when empty, this sentinel will cause a null deref |  | 
| 82         // crash. |  | 
| 83         CustomElementCallbackQueue* sentinel = 0; |  | 
| 84         for (size_t i = 0; i < kNumSentinels; i++) |  | 
| 85             m_flattenedProcessingStack.append(sentinel); |  | 
| 86         ASSERT(s_elementQueueEnd == m_flattenedProcessingStack.size()); |  | 
| 87     } |  | 
| 88 |  | 
| 89     // The start of the element queue on the top of the processing |  | 
| 90     // stack. An offset into instance().m_flattenedProcessingStack. |  | 
| 91     static size_t s_elementQueueStart; |  | 
| 92 |  | 
| 93     // The end of the element queue on the top of the processing |  | 
| 94     // stack. A cache of instance().m_flattenedProcessingStack.size(). |  | 
| 95     static size_t s_elementQueueEnd; |  | 
| 96 |  | 
| 97     static bool inCallbackDeliveryScope() { return s_elementQueueStart; } |  | 
| 98 |  | 
| 99     typedef int ElementQueue; |  | 
| 100     static ElementQueue currentElementQueue() { return ElementQueue(s_elementQue
     ueStart); } |  | 
| 101 |  | 
| 102     static void processElementQueueAndPop(); |  | 
| 103     void processElementQueueAndPop(size_t start, size_t end); |  | 
| 104 |  | 
| 105     // The processing stack, flattened. Element queues lower in the |  | 
| 106     // stack appear toward the head of the vector. The first element |  | 
| 107     // is a null sentinel value. |  | 
| 108     static const size_t kNumSentinels = 1; |  | 
| 109     Vector<CustomElementCallbackQueue*> m_flattenedProcessingStack; |  | 
| 110 }; |  | 
| 111 |  | 
| 112 } |  | 
| 113 |  | 
| 114 #endif // CustomElementCallbackDispatcher_h |  | 
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