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; 38 typedef typename SmallVector<T, N>::const_iterator VIterator; 39 typedef typename SmallVector<T, N>::iterator mutable_iterator; 40 public: 41 typedef size_t size_type; SmallSet()42 SmallSet() {} 43 empty()44 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { 45 return Vector.empty() && Set.empty(); 46 } 47 size()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. count(const T & V)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. insert(const T & V)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> insert(IterT I,IterT E)91 void insert(IterT I, IterT E) { 92 for (; I != E; ++I) 93 insert(*I); 94 } 95 erase(const T & V)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 clear()107 void clear() { 108 Vector.clear(); 109 Set.clear(); 110 } 111 private: isSmall()112 bool isSmall() const { return Set.empty(); } 113 vfind(const T & V)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 130