Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 1 | // Copyright 2006 The RE2 Authors. All Rights Reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // DESCRIPTION |
| 6 | // |
| 7 | // SparseSet<T>(m) is a set of integers in [0, m). |
| 8 | // It requires sizeof(int)*m memory, but it provides |
| 9 | // fast iteration through the elements in the set and fast clearing |
| 10 | // of the set. |
| 11 | // |
| 12 | // Insertion and deletion are constant time operations. |
| 13 | // |
| 14 | // Allocating the set is a constant time operation |
| 15 | // when memory allocation is a constant time operation. |
| 16 | // |
| 17 | // Clearing the set is a constant time operation (unusual!). |
| 18 | // |
| 19 | // Iterating through the set is an O(n) operation, where n |
| 20 | // is the number of items in the set (not O(m)). |
| 21 | // |
| 22 | // The set iterator visits entries in the order they were first |
| 23 | // inserted into the array. It is safe to add items to the set while |
| 24 | // using an iterator: the iterator will visit indices added to the set |
| 25 | // during the iteration, but will not re-visit indices whose values |
| 26 | // change after visiting. Thus SparseSet can be a convenient |
| 27 | // implementation of a work queue. |
| 28 | // |
| 29 | // The SparseSet implementation is NOT thread-safe. It is up to the |
| 30 | // caller to make sure only one thread is accessing the set. (Typically |
| 31 | // these sets are temporary values and used in situations where speed is |
| 32 | // important.) |
| 33 | // |
| 34 | // The SparseSet interface does not present all the usual STL bells and |
| 35 | // whistles. |
| 36 | // |
| 37 | // Implemented with reference to Briggs & Torczon, An Efficient |
| 38 | // Representation for Sparse Sets, ACM Letters on Programming Languages |
| 39 | // and Systems, Volume 2, Issue 1-4 (March-Dec. 1993), pp. 59-69. |
| 40 | // |
| 41 | // For a generalization to sparse array, see sparse_array.h. |
| 42 | |
| 43 | // IMPLEMENTATION |
| 44 | // |
| 45 | // See sparse_array.h for implementation details |
| 46 | |
| 47 | #ifndef RE2_UTIL_SPARSE_SET_H__ |
| 48 | #define RE2_UTIL_SPARSE_SET_H__ |
| 49 | |
| 50 | #include "util/util.h" |
| 51 | |
| 52 | namespace re2 { |
| 53 | |
| 54 | class SparseSet { |
| 55 | public: |
| 56 | SparseSet() |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 57 | : size_(0), max_size_(0), sparse_to_dense_(NULL), dense_(NULL), valgrind_(RunningOnValgrind()) {} |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 58 | |
| 59 | SparseSet(int max_size) { |
| 60 | max_size_ = max_size; |
| 61 | sparse_to_dense_ = new int[max_size]; |
| 62 | dense_ = new int[max_size]; |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 63 | valgrind_ = RunningOnValgrind(); |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 64 | // Don't need to zero the memory, but do so anyway |
| 65 | // to appease Valgrind. |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 66 | if (valgrind_) { |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 67 | for (int i = 0; i < max_size; i++) { |
| 68 | dense_[i] = 0xababababU; |
| 69 | sparse_to_dense_[i] = 0xababababU; |
| 70 | } |
| 71 | } |
| 72 | size_ = 0; |
| 73 | } |
| 74 | |
| 75 | ~SparseSet() { |
| 76 | delete[] sparse_to_dense_; |
| 77 | delete[] dense_; |
| 78 | } |
| 79 | |
| 80 | typedef int* iterator; |
| 81 | typedef const int* const_iterator; |
| 82 | |
| 83 | int size() const { return size_; } |
| 84 | iterator begin() { return dense_; } |
| 85 | iterator end() { return dense_ + size_; } |
| 86 | const_iterator begin() const { return dense_; } |
| 87 | const_iterator end() const { return dense_ + size_; } |
| 88 | |
| 89 | // Change the maximum size of the array. |
| 90 | // Invalidates all iterators. |
| 91 | void resize(int new_max_size) { |
| 92 | if (size_ > new_max_size) |
| 93 | size_ = new_max_size; |
| 94 | if (new_max_size > max_size_) { |
| 95 | int* a = new int[new_max_size]; |
| 96 | if (sparse_to_dense_) { |
| 97 | memmove(a, sparse_to_dense_, max_size_*sizeof a[0]); |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 98 | if (valgrind_) { |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 99 | for (int i = max_size_; i < new_max_size; i++) |
| 100 | a[i] = 0xababababU; |
| 101 | } |
| 102 | delete[] sparse_to_dense_; |
| 103 | } |
| 104 | sparse_to_dense_ = a; |
| 105 | |
| 106 | a = new int[new_max_size]; |
| 107 | if (dense_) { |
| 108 | memmove(a, dense_, size_*sizeof a[0]); |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 109 | if (valgrind_) { |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 110 | for (int i = size_; i < new_max_size; i++) |
| 111 | a[i] = 0xababababU; |
| 112 | } |
| 113 | delete[] dense_; |
| 114 | } |
| 115 | dense_ = a; |
| 116 | } |
| 117 | max_size_ = new_max_size; |
| 118 | } |
| 119 | |
| 120 | // Return the maximum size of the array. |
| 121 | // Indices can be in the range [0, max_size). |
| 122 | int max_size() const { return max_size_; } |
| 123 | |
| 124 | // Clear the array. |
| 125 | void clear() { size_ = 0; } |
| 126 | |
| 127 | // Check whether i is in the array. |
| 128 | bool contains(int i) const { |
| 129 | DCHECK_GE(i, 0); |
| 130 | DCHECK_LT(i, max_size_); |
| 131 | if (static_cast<uint>(i) >= max_size_) { |
| 132 | return false; |
| 133 | } |
| 134 | // Unsigned comparison avoids checking sparse_to_dense_[i] < 0. |
| 135 | return (uint)sparse_to_dense_[i] < (uint)size_ && |
| 136 | dense_[sparse_to_dense_[i]] == i; |
| 137 | } |
| 138 | |
| 139 | // Adds i to the set. |
| 140 | void insert(int i) { |
| 141 | if (!contains(i)) |
| 142 | insert_new(i); |
| 143 | } |
| 144 | |
| 145 | // Set the value at the new index i to v. |
| 146 | // Fast but unsafe: only use if contains(i) is false. |
| 147 | void insert_new(int i) { |
| 148 | if (static_cast<uint>(i) >= max_size_) { |
| 149 | // Semantically, end() would be better here, but we already know |
| 150 | // the user did something stupid, so begin() insulates them from |
| 151 | // dereferencing an invalid pointer. |
| 152 | return; |
| 153 | } |
| 154 | DCHECK(!contains(i)); |
| 155 | DCHECK_LT(size_, max_size_); |
| 156 | sparse_to_dense_[i] = size_; |
| 157 | dense_[size_] = i; |
| 158 | size_++; |
| 159 | } |
| 160 | |
| 161 | // Comparison function for sorting. |
| 162 | // Can sort the sparse array so that future iterations |
| 163 | // will visit indices in increasing order using |
| 164 | // sort(arr.begin(), arr.end(), arr.less); |
| 165 | static bool less(int a, int b) { return a < b; } |
| 166 | |
| 167 | private: |
| 168 | int size_; |
| 169 | int max_size_; |
| 170 | int* sparse_to_dense_; |
| 171 | int* dense_; |
Alexander Gutkin | 0d4c523 | 2013-02-28 13:47:27 +0000 | [diff] [blame] | 172 | bool valgrind_; |
Ian Hodson | 2ee91b4 | 2012-05-14 12:29:36 +0100 | [diff] [blame] | 173 | |
| 174 | DISALLOW_EVIL_CONSTRUCTORS(SparseSet); |
| 175 | }; |
| 176 | |
| 177 | } // namespace re2 |
| 178 | |
| 179 | #endif // RE2_UTIL_SPARSE_SET_H__ |