1/*
2 * Copyright (C) 2008 Apple 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 in the
12 *     documentation and/or other materials provided with the distribution.
13 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14 *     its contributors may be used to endorse or promote products derived
15 *     from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef SegmentedVector_h
30#define SegmentedVector_h
31
32#include <wtf/Vector.h>
33
34namespace WTF {
35
36    // An iterator for SegmentedVector. It supports only the pre ++ operator
37    template <typename T, size_t SegmentSize> class SegmentedVector;
38    template <typename T, size_t SegmentSize> class SegmentedVectorIterator {
39    private:
40        friend class SegmentedVector<T, SegmentSize>;
41    public:
42        typedef SegmentedVectorIterator<T, SegmentSize> Iterator;
43
44        ~SegmentedVectorIterator() { }
45
46        T& operator*() const { return m_vector.m_segments.at(m_segment)->at(m_index); }
47        T* operator->() const { return &m_vector.m_segments.at(m_segment)->at(m_index); }
48
49        // Only prefix ++ operator supported
50        Iterator& operator++()
51        {
52            ASSERT(m_index != SegmentSize);
53            ++m_index;
54            if (m_index >= m_vector.m_segments.at(m_segment)->size())  {
55                if (m_segment + 1 < m_vector.m_segments.size()) {
56                    ASSERT(m_vector.m_segments.at(m_segment)->size() > 0);
57                    ++m_segment;
58                    m_index = 0;
59                } else {
60                    // Points to the "end" symbol
61                    m_segment = 0;
62                    m_index = SegmentSize;
63                }
64            }
65            return *this;
66        }
67
68        bool operator==(const Iterator& other) const
69        {
70            return (m_index == other.m_index && m_segment = other.m_segment && &m_vector == &other.m_vector);
71        }
72
73        bool operator!=(const Iterator& other) const
74        {
75            return (m_index != other.m_index || m_segment != other.m_segment || &m_vector != &other.m_vector);
76        }
77
78        SegmentedVectorIterator& operator=(const SegmentedVectorIterator<T, SegmentSize>& other)
79        {
80            m_vector = other.m_vector;
81            m_segment = other.m_segment;
82            m_index = other.m_index;
83            return *this;
84        }
85
86    private:
87        SegmentedVectorIterator(SegmentedVector<T, SegmentSize>& vector, size_t segment, size_t index)
88            : m_vector(vector)
89            , m_segment(segment)
90            , m_index(index)
91        {
92        }
93
94        SegmentedVector<T, SegmentSize>& m_vector;
95        size_t m_segment;
96        size_t m_index;
97    };
98
99    // SegmentedVector is just like Vector, but it doesn't move the values
100    // stored in its buffer when it grows. Therefore, it is safe to keep
101    // pointers into a SegmentedVector.
102    template <typename T, size_t SegmentSize> class SegmentedVector {
103        friend class SegmentedVectorIterator<T, SegmentSize>;
104    public:
105        typedef SegmentedVectorIterator<T, SegmentSize> Iterator;
106
107        SegmentedVector()
108            : m_size(0)
109        {
110            m_segments.append(&m_inlineSegment);
111        }
112
113        ~SegmentedVector()
114        {
115            deleteAllSegments();
116        }
117
118        size_t size() const { return m_size; }
119        bool isEmpty() const { return !size(); }
120
121        T& at(size_t index)
122        {
123            if (index < SegmentSize)
124                return m_inlineSegment[index];
125            return segmentFor(index)->at(subscriptFor(index));
126        }
127
128        T& operator[](size_t index)
129        {
130            return at(index);
131        }
132
133        T& last()
134        {
135            return at(size() - 1);
136        }
137
138        template <typename U> void append(const U& value)
139        {
140            ++m_size;
141
142            if (m_size <= SegmentSize) {
143                m_inlineSegment.uncheckedAppend(value);
144                return;
145            }
146
147            if (!segmentExistsFor(m_size - 1))
148                m_segments.append(new Segment);
149            segmentFor(m_size - 1)->uncheckedAppend(value);
150        }
151
152        T& alloc()
153        {
154            append<T>(T());
155            return last();
156        }
157
158        void removeLast()
159        {
160            if (m_size <= SegmentSize)
161                m_inlineSegment.removeLast();
162            else
163                segmentFor(m_size - 1)->removeLast();
164            --m_size;
165        }
166
167        void grow(size_t size)
168        {
169            ASSERT(size > m_size);
170            ensureSegmentsFor(size);
171            m_size = size;
172        }
173
174        void clear()
175        {
176            deleteAllSegments();
177            m_segments.resize(1);
178            m_inlineSegment.clear();
179            m_size = 0;
180        }
181
182        Iterator begin()
183        {
184            return Iterator(*this, 0, m_size ? 0 : SegmentSize);
185        }
186
187        Iterator end()
188        {
189            return Iterator(*this, 0, SegmentSize);
190        }
191
192    private:
193        typedef Vector<T, SegmentSize> Segment;
194
195        void deleteAllSegments()
196        {
197            // Skip the first segment, because it's our inline segment, which was
198            // not created by new.
199            for (size_t i = 1; i < m_segments.size(); i++)
200                delete m_segments[i];
201        }
202
203        bool segmentExistsFor(size_t index)
204        {
205            return index / SegmentSize < m_segments.size();
206        }
207
208        Segment* segmentFor(size_t index)
209        {
210            return m_segments[index / SegmentSize];
211        }
212
213        size_t subscriptFor(size_t index)
214        {
215            return index % SegmentSize;
216        }
217
218        void ensureSegmentsFor(size_t size)
219        {
220            size_t segmentCount = m_size / SegmentSize;
221            if (m_size % SegmentSize)
222                ++segmentCount;
223            segmentCount = std::max<size_t>(segmentCount, 1); // We always have at least our inline segment.
224
225            size_t neededSegmentCount = size / SegmentSize;
226            if (size % SegmentSize)
227                ++neededSegmentCount;
228
229            // Fill up to N - 1 segments.
230            size_t end = neededSegmentCount - 1;
231            for (size_t i = segmentCount - 1; i < end; ++i)
232                ensureSegment(i, SegmentSize);
233
234            // Grow segment N to accomodate the remainder.
235            ensureSegment(end, subscriptFor(size - 1) + 1);
236        }
237
238        void ensureSegment(size_t segmentIndex, size_t size)
239        {
240            ASSERT(segmentIndex <= m_segments.size());
241            if (segmentIndex == m_segments.size())
242                m_segments.append(new Segment);
243            m_segments[segmentIndex]->grow(size);
244        }
245
246        size_t m_size;
247        Segment m_inlineSegment;
248        Vector<Segment*, 32> m_segments;
249    };
250
251} // namespace WTF
252
253using WTF::SegmentedVector;
254
255#endif // SegmentedVector_h
256