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