Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

///

/// \file

/// 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 "llvm/ADT/STLExtras.h"

#include "llvm/ADT/iterator.h"

#include "llvm/Support/Compiler.h"

#include "llvm/Support/type_traits.h"

#include <cstddef>

#include <functional>

#include <set>

#include <type_traits>

#include <utility>

namespace llvm {

/// SmallSetIterator - This class implements a const_iterator for SmallSet by

/// delegating to the underlying SmallVector or Set iterators.

template <typename T, unsigned N, typename C>

class SmallSetIterator

    : public iterator_facade_base<SmallSetIterator<T, N, C>,

                                  std::forward_iterator_tag, T> {

private:

  using SetIterTy = typename std::set<T, C>::const_iterator;

  using VecIterTy = typename SmallVector<T, N>::const_iterator;

  using SelfTy = SmallSetIterator<T, N, C>;

  /// Iterators to the parts of the SmallSet containing the data. They are set

  /// depending on isSmall.

  union {

    SetIterTy SetIter;

    VecIterTy VecIter;

  };

  bool isSmall;

public:

  SmallSetIterator(SetIterTy SetIter) : SetIter(SetIter), isSmall(false) {}

  SmallSetIterator(VecIterTy VecIter) : VecIter(VecIter), isSmall(true) {}

  // Spell out destructor, copy/move constructor and assignment operators for

  // MSVC STL, where set<T>::const_iterator is not trivially copy constructible.

  ~SmallSetIterator() {

    if (isSmall)

      VecIter.~VecIterTy();

    else

      SetIter.~SetIterTy();

  }

  SmallSetIterator(const SmallSetIterator &Other) : isSmall(Other.isSmall) {

    if (isSmall)

      VecIter = Other.VecIter;

    else

      // Use placement new, to make sure SetIter is properly constructed, even

      // if it is not trivially copy-able (e.g. in MSVC).

      new (&SetIter) SetIterTy(Other.SetIter);

  }

  SmallSetIterator(SmallSetIterator &&Other) : isSmall(Other.isSmall) {

    if (isSmall)

      VecIter = std::move(Other.VecIter);

    else

      // Use placement new, to make sure SetIter is properly constructed, even

      // if it is not trivially copy-able (e.g. in MSVC).

      new (&SetIter) SetIterTy(std::move(Other.SetIter));

  }

  SmallSetIterator& operator=(const SmallSetIterator& Other) {

    // Call destructor for SetIter, so it gets properly destroyed if it is

    // not trivially destructible in case we are setting VecIter.

    if (!isSmall)

      SetIter.~SetIterTy();

    isSmall = Other.isSmall;

    if (isSmall)

      VecIter = Other.VecIter;

    else

      new (&SetIter) SetIterTy(Other.SetIter);

    return *this;

  }

  SmallSetIterator& operator=(SmallSetIterator&& Other) {

    // Call destructor for SetIter, so it gets properly destroyed if it is

    // not trivially destructible in case we are setting VecIter.

    if (!isSmall)

      SetIter.~SetIterTy();

    isSmall = Other.isSmall;

    if (isSmall)

      VecIter = std::move(Other.VecIter);

    else

      new (&SetIter) SetIterTy(std::move(Other.SetIter));

    return *this;

  }

  bool operator==(const SmallSetIterator &RHS) const {

    if (isSmall != RHS.isSmall)

      return false;

    if (isSmall)

      return VecIter == RHS.VecIter;

    return SetIter == RHS.SetIter;

  }

  SmallSetIterator &operator++() { // Preincrement

    if (isSmall)

      VecIter++;

    else

      SetIter++;

    return *this;

  }

  const T &operator*() const { return isSmall ? *VecIter : *SetIter; }

};

/// 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.

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;

  using VIterator = typename SmallVector<T, N>::const_iterator;

  using SIterator = typename std::set<T, C>::const_iterator;

  using mutable_iterator = typename SmallVector<T, N>::iterator;

  // In small mode SmallPtrSet uses linear search for the elements, so it is

  // not a good idea to choose this value too high. You may consider using a

  // DenseSet<> instead if you expect many elements in the set.

  static_assert(N <= 32, "N should be small");

public:

  using size_type = size_t;

  using const_iterator = SmallSetIterator<T, N, C>;

  SmallSet() = default;

  [[nodiscard]] bool empty() const { return Vector.empty() && Set.empty(); }

  size_type size() const {

    return isSmall() ? Vector.size() : Set.size();

  }

  /// count - Return 1 if the element is in the set, 0 otherwise.

  size_type 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 a pair. The first value of it is an iterator to the inserted

  /// element or the existing element in the set. The second value is true

  /// if the element is inserted (it was not in the set before).

  std::pair<const_iterator, bool> insert(const T &V) {

    if (!isSmall()) {

      auto [I, Inserted] = Set.insert(V);

      return std::make_pair(const_iterator(I), Inserted);

    }

    VIterator I = vfind(V);

    if (I != Vector.end())    // Don't reinsert if it already exists.

      return std::make_pair(const_iterator(I), false);

    if (Vector.size() < N) {

      Vector.push_back(V);

      return std::make_pair(const_iterator(std::prev(Vector.end())), true);

    }

    // Otherwise, grow from vector to set.

    while (!Vector.empty()) {

      Set.insert(Vector.back());

      Vector.pop_back();

    }

    return std::make_pair(const_iterator(Set.insert(V).first), 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();

  }

  const_iterator begin() const {

    if (isSmall())

      return {Vector.begin()};

    return {Set.begin()};

  }

  const_iterator end() const {

    if (isSmall())

      return {Vector.end()};

    return {Set.end()};

  }

  /// Check if the SmallSet contains the given element.

  bool contains(const T &V) const {

    if (isSmall())

      return vfind(V) != Vector.end();

    return Set.find(V) != Set.end();

  }

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> {};

/// Equality comparison for SmallSet.

///

/// Iterates over elements of LHS confirming that each element is also a member

/// of RHS, and that RHS contains no additional values.

/// Equivalent to N calls to RHS.count.

/// For small-set mode amortized complexity is O(N^2)

/// For large-set mode amortized complexity is linear, worst case is O(N^2) (if

/// every hash collides).

template <typename T, unsigned LN, unsigned RN, typename C>

bool operator==(const SmallSet<T, LN, C> &LHS, const SmallSet<T, RN, C> &RHS) {

  if (LHS.size() != RHS.size())

    return false;

  // All elements in LHS must also be in RHS

  return all_of(LHS, [&RHS](const T &E) { return RHS.count(E); });

}

/// Inequality comparison for SmallSet.

///

/// Equivalent to !(LHS == RHS). See operator== for performance notes.

template <typename T, unsigned LN, unsigned RN, typename C>

bool operator!=(const SmallSet<T, LN, C> &LHS, const SmallSet<T, RN, C> &RHS) {

  return !(LHS == RHS);

}

} // end namespace llvm

#endif // LLVM_ADT_SMALLSET_H