text: /*
   * Copyright (C) 2014-2016 Apple Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
   * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   * THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include <wtf/DoublyLinkedList.h>
  #include <wtf/Forward.h>
  
  namespace JSC {
  
  template <typename T>
  class GCArraySegment : public DoublyLinkedListNode<GCArraySegment<T>> {
      friend class WTF::DoublyLinkedListNode<GCArraySegment<T>>;
  public:
      GCArraySegment()
          : DoublyLinkedListNode<GCArraySegment<T>>()
  #if !ASSERT_DISABLED
          , m_top(0)
  #endif
      {
      }
  
      static GCArraySegment* create();
      static void destroy(GCArraySegment*);
  
      T* data()
      {
          return bitwise_cast<T*>(this + 1);
      }
  
      static const size_t blockSize = 4 * KB;
  
      GCArraySegment* m_prev;
      GCArraySegment* m_next;
  #if !ASSERT_DISABLED
      size_t m_top;
  #endif
  };
  
  template <typename T> class GCSegmentedArrayIterator;
  
  template <typename T>
  class GCSegmentedArray {
      WTF_MAKE_FAST_ALLOCATED;
      WTF_MAKE_NONCOPYABLE(GCSegmentedArray);
      friend class GCSegmentedArrayIterator<T>;
      friend class GCSegmentedArrayIterator<const T>;
  public:
      GCSegmentedArray();
      ~GCSegmentedArray();
  
      void append(T);
  
      bool canRemoveLast();
      const T removeLast();
      bool refill();
      
      size_t size();
      bool isEmpty();
  
      void fillVector(Vector<T>&);
      void clear();
  
      typedef GCSegmentedArrayIterator<T> iterator;
      iterator begin() const { return GCSegmentedArrayIterator<T>(m_segments.head(), m_top); }
      iterator end() const { return GCSegmentedArrayIterator<T>(); }
  
  protected:
      template <size_t size> struct CapacityFromSize {
          static const size_t value = (size - sizeof(GCArraySegment<T>)) / sizeof(T);
      };
  
      void expand();
      
      size_t postIncTop();
      size_t preDecTop();
      void setTopForFullSegment();
      void setTopForEmptySegment();
      size_t top();
      
      void validatePrevious();
  
      DoublyLinkedList<GCArraySegment<T>> m_segments;
  
      JS_EXPORT_PRIVATE static const size_t s_segmentCapacity = CapacityFromSize<GCArraySegment<T>::blockSize>::value;
      size_t m_top;
      size_t m_numberOfSegments;
  };
  
  template <typename T>
  class GCSegmentedArrayIterator {
      friend class GCSegmentedArray<T>;
  public:
      GCSegmentedArrayIterator()
          : m_currentSegment(0)
          , m_currentOffset(0)
      {
      }
  
      T& get() { return m_currentSegment->data()[m_currentOffset]; }
      T& operator*() { return get(); }
      T& operator->() { return get(); }
  
      bool operator==(const GCSegmentedArrayIterator& other)
      {
          return m_currentSegment == other.m_currentSegment && m_currentOffset == other.m_currentOffset;
      }
  
      bool operator!=(const GCSegmentedArrayIterator& other)
      {
          return !(*this == other);
      }
  
      GCSegmentedArrayIterator& operator++()
      {
          ASSERT(m_currentSegment);
  
          m_currentOffset++;
  
          if (m_currentOffset >= m_offsetLimit) {
              m_currentSegment = m_currentSegment->next();
              m_currentOffset = 0;
              m_offsetLimit = GCSegmentedArray<T>::s_segmentCapacity;
          }
  
          return *this;
      }
  
  private:
      GCSegmentedArrayIterator(GCArraySegment<T>* start, size_t top)
          : m_currentSegment(start)
          , m_currentOffset(0)
          , m_offsetLimit(top)
      {
          if (!m_offsetLimit)
              m_currentSegment = nullptr;
      }
  
      GCArraySegment<T>* m_currentSegment;
      size_t m_currentOffset;
      size_t m_offsetLimit;
  };
  
  } // namespace JSC
  
  