third_party/WebKit/Source/core/dom/custom/CustomElementProcessingStack.h

   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 CustomElementProcessingStack_h
  32 #define CustomElementProcessingStack_h
  33
  34 #include "core/CoreExport.h"
  35 #include "core/dom/custom/CustomElementCallbackQueue.h"
  36 #include "wtf/Vector.h"
  37
  38 namespace blink {
  39
  40 class CORE_EXPORT CustomElementProcessingStack : public NoBaseWillBeGarbageCollectedFinalized<CustomElementProcessingStack> {
  41     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(CustomElementProcessingStack);
  42     WTF_MAKE_NONCOPYABLE(CustomElementProcessingStack);
  43 public:
  44     // This is stack allocated in many DOM callbacks. Make it cheap.
  45     class CallbackDeliveryScope {
  46         STACK_ALLOCATED();
  47     public:
  48         CallbackDeliveryScope()
  49             : m_savedElementQueueStart(s_elementQueueStart)
  50         {
  51             s_elementQueueStart = s_elementQueueEnd;
  52         }
  53
  54         ~CallbackDeliveryScope()
  55         {
  56             if (s_elementQueueStart != s_elementQueueEnd)
  57                 processElementQueueAndPop();
  58             s_elementQueueStart = m_savedElementQueueStart;
  59         }
  60
  61     private:
  62         size_t m_savedElementQueueStart;
  63     };
  64
  65     static bool inCallbackDeliveryScope() { return s_elementQueueStart; }
  66
  67     static CustomElementProcessingStack& instance();
  68     void enqueue(CustomElementCallbackQueue*);
  69
  70     DECLARE_TRACE();
  71
  72 private:
  73     CustomElementProcessingStack()
  74     {
  75         // Add a null element as a sentinel. This makes it possible to
  76         // identify elements queued when there is no
  77         // CallbackDeliveryScope active. Also, if the processing stack
  78         // is popped when empty, this sentinel will cause a null deref
  79         // crash.
  80         CustomElementCallbackQueue* sentinel = 0;
  81         for (size_t i = 0; i < kNumSentinels; i++)
  82             m_flattenedProcessingStack.append(sentinel);
  83         ASSERT(s_elementQueueEnd == m_flattenedProcessingStack.size());
  84     }
  85
  86     // The start of the element queue on the top of the processing
  87     // stack. An offset into instance().m_flattenedProcessingStack.
  88     static size_t s_elementQueueStart;
  89
  90     // The end of the element queue on the top of the processing
  91     // stack. A cache of instance().m_flattenedProcessingStack.size().
  92     static size_t s_elementQueueEnd;
  93
  94     static CustomElementCallbackQueue::ElementQueueId currentElementQueue() { return CustomElementCallbackQueue::ElementQueueId(s_elementQueueStart); }
  95
  96     static void processElementQueueAndPop();
  97     void processElementQueueAndPop(size_t start, size_t end);
  98
  99     // The processing stack, flattened. Element queues lower in the
 100     // stack appear toward the head of the vector. The first element
 101     // is a null sentinel value.
 102     static const size_t kNumSentinels = 1;
 103     WillBeHeapVector<RawPtrWillBeMember<CustomElementCallbackQueue>> m_flattenedProcessingStack;
 104 };
 105
 106 } // namespace blink
 107
 108 #endif // CustomElementProcessingStack_h