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/SmallVector.h" 18 #include "llvm/ADT/SmallPtrSet.h" 19 #include <set> 20 21 namespace llvm { 22 23 /// SmallSet - This maintains a set of unique values, optimizing for the case 24 /// when the set is small (less than N). In this case, the set can be 25 /// maintained with no mallocs. If the set gets large, we expand to using an 26 /// std::set to maintain reasonable lookup times. 27 /// 28 /// Note that this set does not provide a way to iterate over members in the 29 /// set. 30 template <typename T, unsigned N> 31 class SmallSet { 32 /// Use a SmallVector to hold the elements here (even though it will never 33 /// reach its 'large' stage) to avoid calling the default ctors of elements 34 /// we will never use. 35 SmallVector<T, N> Vector; 36 std::set<T> Set; 37 typedef typename SmallVector<T, N>::const_iterator VIterator; 38 typedef typename SmallVector<T, N>::iterator mutable_iterator; 39 public: 40 SmallSet() {} 41 42 bool empty() const { return Vector.empty() && Set.empty(); } 43 unsigned size() const { 44 return isSmall() ? Vector.size() : Set.size(); 45 } 46 47 /// count - Return true if the element is in the set. 48 bool count(const T &V) const { 49 if (isSmall()) { 50 // Since the collection is small, just do a linear search. 51 return vfind(V) != Vector.end(); 52 } else { 53 return Set.count(V); 54 } 55 } 56 57 /// insert - Insert an element into the set if it isn't already there. 58 bool insert(const T &V) { 59 if (!isSmall()) 60 return Set.insert(V).second; 61 62 VIterator I = vfind(V); 63 if (I != Vector.end()) // Don't reinsert if it already exists. 64 return false; 65 if (Vector.size() < N) { 66 Vector.push_back(V); 67 return true; 68 } 69 70 // Otherwise, grow from vector to set. 71 while (!Vector.empty()) { 72 Set.insert(Vector.back()); 73 Vector.pop_back(); 74 } 75 Set.insert(V); 76 return true; 77 } 78 79 template <typename IterT> 80 void insert(IterT I, IterT E) { 81 for (; I != E; ++I) 82 insert(*I); 83 } 84 85 bool erase(const T &V) { 86 if (!isSmall()) 87 return Set.erase(V); 88 for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I) 89 if (*I == V) { 90 Vector.erase(I); 91 return true; 92 } 93 return false; 94 } 95 96 void clear() { 97 Vector.clear(); 98 Set.clear(); 99 } 100 private: 101 bool isSmall() const { return Set.empty(); } 102 103 VIterator vfind(const T &V) const { 104 for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I) 105 if (*I == V) 106 return I; 107 return Vector.end(); 108 } 109 }; 110 111 /// If this set is of pointer values, transparently switch over to using 112 /// SmallPtrSet for performance. 113 template <typename PointeeType, unsigned N> 114 class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {}; 115 116 } // end namespace llvm 117 118 #endif 119
