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119 lines
3.2 KiB
C++
119 lines
3.2 KiB
C++
//===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the SmallSet class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_SMALLSET_H
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#define LLVM_ADT_SMALLSET_H
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include <set>
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namespace llvm {
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/// SmallSet - This maintains a set of unique values, optimizing for the case
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/// when the set is small (less than N). In this case, the set can be
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/// maintained with no mallocs. If the set gets large, we expand to using an
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/// std::set to maintain reasonable lookup times.
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///
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/// Note that this set does not provide a way to iterate over members in the
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/// set.
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template <typename T, unsigned N>
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class SmallSet {
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/// Use a SmallVector to hold the elements here (even though it will never
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/// reach it's 'large' stage) to avoid calling the default ctors of elements
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/// we will never use.
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SmallVector<T, N> Vector;
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std::set<T> Set;
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typedef typename SmallVector<T, N>::const_iterator VIterator;
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typedef typename SmallVector<T, N>::iterator mutable_iterator;
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public:
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SmallSet() {}
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bool empty() const { return Vector.empty() && Set.empty(); }
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unsigned size() const {
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return isSmall() ? Vector.size() : Set.size();
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}
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/// count - Return true if the element is in the set.
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bool count(const T &V) const {
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if (isSmall()) {
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// Since the collection is small, just do a linear search.
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return vfind(V) != Vector.end();
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} else {
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return Set.count(V);
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}
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}
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/// insert - Insert an element into the set if it isn't already there.
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bool insert(const T &V) {
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if (!isSmall())
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return Set.insert(V).second;
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VIterator I = vfind(V);
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if (I != Vector.end()) // Don't reinsert if it already exists.
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return false;
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if (Vector.size() < N) {
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Vector.push_back(V);
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return true;
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}
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// Otherwise, grow from vector to set.
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while (!Vector.empty()) {
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Set.insert(Vector.back());
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Vector.pop_back();
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}
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Set.insert(V);
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return true;
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}
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template <typename IterT>
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void insert(IterT I, IterT E) {
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for (; I != E; ++I)
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insert(*I);
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}
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bool erase(const T &V) {
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if (!isSmall())
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return Set.erase(V);
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for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
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if (*I == V) {
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Vector.erase(I);
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return true;
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}
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return false;
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}
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void clear() {
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Vector.clear();
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Set.clear();
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}
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private:
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bool isSmall() const { return Set.empty(); }
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VIterator vfind(const T &V) const {
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for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
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if (*I == V)
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return I;
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return Vector.end();
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}
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};
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/// If this set is of pointer values, transparently switch over to using
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/// SmallPtrSet for performance.
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template <typename PointeeType, unsigned N>
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class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {};
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} // end namespace llvm
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#endif
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