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//===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the SmallSet class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_SMALLSET_H
#define LLVM_ADT_SMALLSET_H
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include <set>
namespace llvm {
/// SmallSet - This maintains a set of unique values, optimizing for the case
/// when the set is small (less than N). In this case, the set can be
/// maintained with no mallocs. If the set gets large, we expand to using an
/// std::set to maintain reasonable lookup times.
///
/// Note that this set does not provide a way to iterate over members in the
/// set.
template <typename T, unsigned N, typename C = std::less<T> >
class SmallSet {
/// Use a SmallVector to hold the elements here (even though it will never
/// reach its 'large' stage) to avoid calling the default ctors of elements
/// we will never use.
SmallVector<T, N> Vector;
std::set<T, C> Set;
typedef typename SmallVector<T, N>::const_iterator VIterator;
typedef typename SmallVector<T, N>::iterator mutable_iterator;
public:
SmallSet() {}
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
return Vector.empty() && Set.empty();
}
unsigned size() const {
return isSmall() ? Vector.size() : Set.size();
}
/// count - Return 1 if the element is in the set, 0 otherwise.
unsigned count(const T &V) const {
if (isSmall()) {
// Since the collection is small, just do a linear search.
return vfind(V) == Vector.end() ? 0 : 1;
} else {
return Set.count(V);
}
}
/// insert - Insert an element into the set if it isn't already there.
/// Returns true if the element is inserted (it was not in the set before).
bool insert(const T &V) {
if (!isSmall())
return Set.insert(V).second;
VIterator I = vfind(V);
if (I != Vector.end()) // Don't reinsert if it already exists.
return false;
if (Vector.size() < N) {
Vector.push_back(V);
return true;
}
// Otherwise, grow from vector to set.
while (!Vector.empty()) {
Set.insert(Vector.back());
Vector.pop_back();
}
Set.insert(V);
return true;
}
template <typename IterT>
void insert(IterT I, IterT E) {
for (; I != E; ++I)
insert(*I);
}
bool erase(const T &V) {
if (!isSmall())
return Set.erase(V);
for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
if (*I == V) {
Vector.erase(I);
return true;
}
return false;
}
void clear() {
Vector.clear();
Set.clear();
}
private:
bool isSmall() const { return Set.empty(); }
VIterator vfind(const T &V) const {
for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
if (*I == V)
return I;
return Vector.end();
}
};
/// If this set is of pointer values, transparently switch over to using
/// SmallPtrSet for performance.
template <typename PointeeType, unsigned N>
class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {};
} // end namespace llvm
#endif
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