include/llvm/ADT/SmallSet.h - llvm-project/llvm - Git at Google

 //===- 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 key_type = T;
   using size_type = size_t;
   using value_type = 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
	//===- 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 key_type = T;
	using size_type = size_t;
	using value_type = 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