LLVM  3.7.0
SmallSet.h
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1 //===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the SmallSet class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ADT_SMALLSET_H
15 #define LLVM_ADT_SMALLSET_H
16 
17 #include "llvm/ADT/None.h"
18 #include "llvm/ADT/SmallPtrSet.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include <set>
21 
22 namespace llvm {
23 
24 /// SmallSet - This maintains a set of unique values, optimizing for the case
25 /// when the set is small (less than N). In this case, the set can be
26 /// maintained with no mallocs. If the set gets large, we expand to using an
27 /// std::set to maintain reasonable lookup times.
28 ///
29 /// Note that this set does not provide a way to iterate over members in the
30 /// set.
31 template <typename T, unsigned N, typename C = std::less<T> >
32 class SmallSet {
33  /// Use a SmallVector to hold the elements here (even though it will never
34  /// reach its 'large' stage) to avoid calling the default ctors of elements
35  /// we will never use.
36  SmallVector<T, N> Vector;
37  std::set<T, C> Set;
40 public:
41  typedef size_t size_type;
42  SmallSet() {}
43 
45  return Vector.empty() && Set.empty();
46  }
47 
48  size_type size() const {
49  return isSmall() ? Vector.size() : Set.size();
50  }
51 
52  /// count - Return 1 if the element is in the set, 0 otherwise.
53  size_type count(const T &V) const {
54  if (isSmall()) {
55  // Since the collection is small, just do a linear search.
56  return vfind(V) == Vector.end() ? 0 : 1;
57  } else {
58  return Set.count(V);
59  }
60  }
61 
62  /// insert - Insert an element into the set if it isn't already there.
63  /// Returns true if the element is inserted (it was not in the set before).
64  /// The first value of the returned pair is unused and provided for
65  /// partial compatibility with the standard library self-associative container
66  /// concept.
67  // FIXME: Add iterators that abstract over the small and large form, and then
68  // return those here.
69  std::pair<NoneType, bool> insert(const T &V) {
70  if (!isSmall())
71  return std::make_pair(None, Set.insert(V).second);
72 
73  VIterator I = vfind(V);
74  if (I != Vector.end()) // Don't reinsert if it already exists.
75  return std::make_pair(None, false);
76  if (Vector.size() < N) {
77  Vector.push_back(V);
78  return std::make_pair(None, true);
79  }
80 
81  // Otherwise, grow from vector to set.
82  while (!Vector.empty()) {
83  Set.insert(Vector.back());
84  Vector.pop_back();
85  }
86  Set.insert(V);
87  return std::make_pair(None, true);
88  }
89 
90  template <typename IterT>
91  void insert(IterT I, IterT E) {
92  for (; I != E; ++I)
93  insert(*I);
94  }
95 
96  bool erase(const T &V) {
97  if (!isSmall())
98  return Set.erase(V);
99  for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
100  if (*I == V) {
101  Vector.erase(I);
102  return true;
103  }
104  return false;
105  }
106 
107  void clear() {
108  Vector.clear();
109  Set.clear();
110  }
111 private:
112  bool isSmall() const { return Set.empty(); }
113 
114  VIterator vfind(const T &V) const {
115  for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
116  if (*I == V)
117  return I;
118  return Vector.end();
119  }
120 };
121 
122 /// If this set is of pointer values, transparently switch over to using
123 /// SmallPtrSet for performance.
124 template <typename PointeeType, unsigned N>
125 class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {};
126 
127 } // end namespace llvm
128 
129 #endif
#define LLVM_ATTRIBUTE_UNUSED_RESULT
Definition: Compiler.h:128
bool erase(const T &V)
Definition: SmallSet.h:96
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const
Definition: SmallSet.h:44
size_type size() const
Definition: SmallSet.h:48
void clear()
Definition: SmallSet.h:107
void insert(IterT I, IterT E)
Definition: SmallSet.h:91
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:32
std::pair< NoneType, bool > insert(const T &V)
insert - Insert an element into the set if it isn't already there.
Definition: SmallSet.h:69
size_type count(const T &V) const
count - Return 1 if the element is in the set, 0 otherwise.
Definition: SmallSet.h:53
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
size_t size_type
Definition: SmallSet.h:41
#define I(x, y, z)
Definition: MD5.cpp:54
#define N