/*

 * Copyright (C) 2008 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.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     its contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE 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 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.

 */

#ifndef SegmentedVector_h

#define SegmentedVector_h

#include <wtf/Vector.h>

namespace WTF {

    // An iterator for SegmentedVector. It supports only the pre ++ operator

    template <typename T, size_t SegmentSize> class SegmentedVector;

    template <typename T, size_t SegmentSize> class SegmentedVectorIterator {

    private:

        friend class SegmentedVector<T, SegmentSize>;

    public:

        typedef SegmentedVectorIterator<T, SegmentSize> Iterator;

        ~SegmentedVectorIterator() { }

        T& operator*() const { return m_vector.m_segments.at(m_segment)->at(m_index); }

        T* operator->() const { return &m_vector.m_segments.at(m_segment)->at(m_index); }

        // Only prefix ++ operator supported

        Iterator& operator++()

        {

            ASSERT(m_index != SegmentSize);

            ++m_index;

            if (m_index >= m_vector.m_segments.at(m_segment)->size())  {

                if (m_segment + 1 < m_vector.m_segments.size()) {

                    ASSERT(m_vector.m_segments.at(m_segment)->size() > 0);

                    ++m_segment;

                    m_index = 0;

                } else {

                    // Points to the "end" symbol

                    m_segment = 0;

                    m_index = SegmentSize;

                }

            }

            return *this;

        }

        bool operator==(const Iterator& other) const

        {

            return (m_index == other.m_index && m_segment = other.m_segment && &m_vector == &other.m_vector);

        }

        bool operator!=(const Iterator& other) const

        {

            return (m_index != other.m_index || m_segment != other.m_segment || &m_vector != &other.m_vector);

        }

        SegmentedVectorIterator& operator=(const SegmentedVectorIterator<T, SegmentSize>& other)

        {

            m_vector = other.m_vector;

            m_segment = other.m_segment;

            m_index = other.m_index;

            return *this;

        }

    private:

        SegmentedVectorIterator(SegmentedVector<T, SegmentSize>& vector, size_t segment, size_t index)

            : m_vector(vector)

            , m_segment(segment)

            , m_index(index)

        {

        }

        SegmentedVector<T, SegmentSize>& m_vector;

        size_t m_segment;

        size_t m_index;

    };

    // SegmentedVector is just like Vector, but it doesn't move the values

    // stored in its buffer when it grows. Therefore, it is safe to keep

    // pointers into a SegmentedVector.

    template <typename T, size_t SegmentSize> class SegmentedVector {

        friend class SegmentedVectorIterator<T, SegmentSize>;

    public:

        typedef SegmentedVectorIterator<T, SegmentSize> Iterator;

        SegmentedVector()

            : m_size(0)

        {

            m_segments.append(&m_inlineSegment);

        }

        ~SegmentedVector()

        {

            deleteAllSegments();

        }

        size_t size() const { return m_size; }

        bool isEmpty() const { return !size(); }

        T& at(size_t index)

        {

            if (index < SegmentSize)

                return m_inlineSegment[index];

            return segmentFor(index)->at(subscriptFor(index));

        }

        T& operator[](size_t index)

        {

            return at(index);

        }

        T& last()

        {

            return at(size() - 1);

        }

        template <typename U> void append(const U& value)

        {

            ++m_size;

            if (m_size <= SegmentSize) {

                m_inlineSegment.uncheckedAppend(value);

                return;

            }

            if (!segmentExistsFor(m_size - 1))

                m_segments.append(new Segment);

            segmentFor(m_size - 1)->uncheckedAppend(value);

        }

        T& alloc()

        {

            append<T>(T());

            return last();

        }

        void removeLast()

        {

            if (m_size <= SegmentSize)

                m_inlineSegment.removeLast();

            else

                segmentFor(m_size - 1)->removeLast();

            --m_size;

        }

        void grow(size_t size)

        {

            ASSERT(size > m_size);

            ensureSegmentsFor(size);

            m_size = size;

        }

        void clear()

        {

            deleteAllSegments();

            m_segments.resize(1);

            m_inlineSegment.clear();

            m_size = 0;

        }

        Iterator begin()

        {

            return Iterator(*this, 0, m_size ? 0 : SegmentSize);

        }

        Iterator end()

        {

            return Iterator(*this, 0, SegmentSize);

        }

    private:

        typedef Vector<T, SegmentSize> Segment;

        void deleteAllSegments()

        {

            // Skip the first segment, because it's our inline segment, which was

            // not created by new.

            for (size_t i = 1; i < m_segments.size(); i++)

                delete m_segments[i];

        }

        bool segmentExistsFor(size_t index)

        {

            return index / SegmentSize < m_segments.size();

        }

        Segment* segmentFor(size_t index)

        {

            return m_segments[index / SegmentSize];

        }

        size_t subscriptFor(size_t index)

        {

            return index % SegmentSize;

        }

        void ensureSegmentsFor(size_t size)

        {

            size_t segmentCount = m_size / SegmentSize;

            if (m_size % SegmentSize)

                ++segmentCount;

            segmentCount = std::max<size_t>(segmentCount, 1); // We always have at least our inline segment.

            size_t neededSegmentCount = size / SegmentSize;

            if (size % SegmentSize)

                ++neededSegmentCount;

            // Fill up to N - 1 segments.

            size_t end = neededSegmentCount - 1;

            for (size_t i = segmentCount - 1; i < end; ++i)

                ensureSegment(i, SegmentSize);

            // Grow segment N to accomodate the remainder.

            ensureSegment(end, subscriptFor(size - 1) + 1);

        }

        void ensureSegment(size_t segmentIndex, size_t size)

        {

            ASSERT(segmentIndex <= m_segments.size());

            if (segmentIndex == m_segments.size())

                m_segments.append(new Segment);

            m_segments[segmentIndex]->grow(size);

        }

        size_t m_size;

        Segment m_inlineSegment;

        Vector<Segment*, 32> m_segments;

    };

} // namespace WTF

using WTF::SegmentedVector;

#endif // SegmentedVector_h