1 //==-- llvm/ADT/ilist.h - Intrusive Linked List Template ---------*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines classes to implement an intrusive doubly linked list class
11 // (i.e. each node of the list must contain a next and previous field for the
14 // The ilist_traits trait class is used to gain access to the next and previous
15 // fields of the node type that the list is instantiated with. If it is not
16 // specialized, the list defaults to using the getPrev(), getNext() method calls
17 // to get the next and previous pointers.
19 // The ilist class itself, should be a plug in replacement for list, assuming
20 // that the nodes contain next/prev pointers. This list replacement does not
21 // provide a constant time size() method, so be careful to use empty() when you
22 // really want to know if it's empty.
24 // The ilist class is implemented by allocating a 'tail' node when the list is
25 // created (using ilist_traits<>::createSentinel()). This tail node is
26 // absolutely required because the user must be able to compute end()-1. Because
27 // of this, users of the direct next/prev links will see an extra link on the
28 // end of the list, which should be ignored.
30 // Requirements for a user of this list:
32 // 1. The user must provide {g|s}et{Next|Prev} methods, or specialize
33 // ilist_traits to provide an alternate way of getting and setting next and
36 //===----------------------------------------------------------------------===//
38 #ifndef LLVM_ADT_ILIST_H
39 #define LLVM_ADT_ILIST_H
41 #include "llvm/Support/Compiler.h"
49 template<typename NodeTy, typename Traits> class iplist;
50 template<typename NodeTy> class ilist_iterator;
52 /// ilist_nextprev_traits - A fragment for template traits for intrusive list
53 /// that provides default next/prev implementations for common operations.
55 template<typename NodeTy>
56 struct ilist_nextprev_traits {
57 static NodeTy *getPrev(NodeTy *N) { return N->getPrev(); }
58 static NodeTy *getNext(NodeTy *N) { return N->getNext(); }
59 static const NodeTy *getPrev(const NodeTy *N) { return N->getPrev(); }
60 static const NodeTy *getNext(const NodeTy *N) { return N->getNext(); }
62 static void setPrev(NodeTy *N, NodeTy *Prev) { N->setPrev(Prev); }
63 static void setNext(NodeTy *N, NodeTy *Next) { N->setNext(Next); }
66 template<typename NodeTy>
69 /// ilist_sentinel_traits - A fragment for template traits for intrusive list
70 /// that provides default sentinel implementations for common operations.
72 /// ilist_sentinel_traits implements a lazy dynamic sentinel allocation
73 /// strategy. The sentinel is stored in the prev field of ilist's Head.
75 template<typename NodeTy>
76 struct ilist_sentinel_traits {
77 /// createSentinel - create the dynamic sentinel
78 static NodeTy *createSentinel() { return new NodeTy(); }
80 /// destroySentinel - deallocate the dynamic sentinel
81 static void destroySentinel(NodeTy *N) { delete N; }
83 /// provideInitialHead - when constructing an ilist, provide a starting
84 /// value for its Head
85 /// @return null node to indicate that it needs to be allocated later
86 static NodeTy *provideInitialHead() { return nullptr; }
88 /// ensureHead - make sure that Head is either already
89 /// initialized or assigned a fresh sentinel
90 /// @return the sentinel
91 static NodeTy *ensureHead(NodeTy *&Head) {
93 Head = ilist_traits<NodeTy>::createSentinel();
94 ilist_traits<NodeTy>::noteHead(Head, Head);
95 ilist_traits<NodeTy>::setNext(Head, nullptr);
98 return ilist_traits<NodeTy>::getPrev(Head);
101 /// noteHead - stash the sentinel into its default location
102 static void noteHead(NodeTy *NewHead, NodeTy *Sentinel) {
103 ilist_traits<NodeTy>::setPrev(NewHead, Sentinel);
107 template <typename NodeTy> class ilist_half_node;
108 template <typename NodeTy> class ilist_node;
110 /// Traits with an embedded ilist_node as a sentinel.
112 /// FIXME: The downcast in createSentinel() is UB.
113 template <typename NodeTy> struct ilist_embedded_sentinel_traits {
114 /// Get hold of the node that marks the end of the list.
115 NodeTy *createSentinel() const {
116 // Since i(p)lists always publicly derive from their corresponding traits,
117 // placing a data member in this class will augment the i(p)list. But since
118 // the NodeTy is expected to be publicly derive from ilist_node<NodeTy>,
119 // there is a legal viable downcast from it to NodeTy. We use this trick to
120 // superimpose an i(p)list with a "ghostly" NodeTy, which becomes the
121 // sentinel. Dereferencing the sentinel is forbidden (save the
122 // ilist_node<NodeTy>), so no one will ever notice the superposition.
123 return static_cast<NodeTy *>(&Sentinel);
125 static void destroySentinel(NodeTy *) {}
127 NodeTy *provideInitialHead() const { return createSentinel(); }
128 NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
129 static void noteHead(NodeTy *, NodeTy *) {}
132 mutable ilist_node<NodeTy> Sentinel;
135 /// Trait with an embedded ilist_half_node as a sentinel.
137 /// FIXME: The downcast in createSentinel() is UB.
138 template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {
139 /// Get hold of the node that marks the end of the list.
140 NodeTy *createSentinel() const {
141 // See comment in ilist_embedded_sentinel_traits::createSentinel().
142 return static_cast<NodeTy *>(&Sentinel);
144 static void destroySentinel(NodeTy *) {}
146 NodeTy *provideInitialHead() const { return createSentinel(); }
147 NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
148 static void noteHead(NodeTy *, NodeTy *) {}
151 mutable ilist_half_node<NodeTy> Sentinel;
154 /// ilist_node_traits - A fragment for template traits for intrusive list
155 /// that provides default node related operations.
157 template<typename NodeTy>
158 struct ilist_node_traits {
159 static NodeTy *createNode(const NodeTy &V) { return new NodeTy(V); }
160 static void deleteNode(NodeTy *V) { delete V; }
162 void addNodeToList(NodeTy *) {}
163 void removeNodeFromList(NodeTy *) {}
164 void transferNodesFromList(ilist_node_traits & /*SrcTraits*/,
165 ilist_iterator<NodeTy> /*first*/,
166 ilist_iterator<NodeTy> /*last*/) {}
169 /// ilist_default_traits - Default template traits for intrusive list.
170 /// By inheriting from this, you can easily use default implementations
171 /// for all common operations.
173 template<typename NodeTy>
174 struct ilist_default_traits : public ilist_nextprev_traits<NodeTy>,
175 public ilist_sentinel_traits<NodeTy>,
176 public ilist_node_traits<NodeTy> {
179 // Template traits for intrusive list. By specializing this template class, you
180 // can change what next/prev fields are used to store the links...
181 template<typename NodeTy>
182 struct ilist_traits : public ilist_default_traits<NodeTy> {};
184 // Const traits are the same as nonconst traits...
185 template<typename Ty>
186 struct ilist_traits<const Ty> : public ilist_traits<Ty> {};
188 //===----------------------------------------------------------------------===//
189 // ilist_iterator<Node> - Iterator for intrusive list.
191 template<typename NodeTy>
193 : public std::iterator<std::bidirectional_iterator_tag, NodeTy, ptrdiff_t> {
196 typedef ilist_traits<NodeTy> Traits;
197 typedef std::iterator<std::bidirectional_iterator_tag,
198 NodeTy, ptrdiff_t> super;
200 typedef typename super::value_type value_type;
201 typedef typename super::difference_type difference_type;
202 typedef typename super::pointer pointer;
203 typedef typename super::reference reference;
207 // ilist_iterator is not a random-access iterator, but it has an
208 // implicit conversion to pointer-type, which is. Declare (but
209 // don't define) these functions as private to help catch
210 // accidental misuse.
211 void operator[](difference_type) const;
212 void operator+(difference_type) const;
213 void operator-(difference_type) const;
214 void operator+=(difference_type) const;
215 void operator-=(difference_type) const;
216 template<class T> void operator<(T) const;
217 template<class T> void operator<=(T) const;
218 template<class T> void operator>(T) const;
219 template<class T> void operator>=(T) const;
220 template<class T> void operator-(T) const;
223 ilist_iterator(pointer NP) : NodePtr(NP) {}
224 ilist_iterator(reference NR) : NodePtr(&NR) {}
225 ilist_iterator() : NodePtr(nullptr) {}
227 // This is templated so that we can allow constructing a const iterator from
228 // a nonconst iterator...
229 template<class node_ty>
230 ilist_iterator(const ilist_iterator<node_ty> &RHS)
231 : NodePtr(RHS.getNodePtrUnchecked()) {}
233 // This is templated so that we can allow assigning to a const iterator from
234 // a nonconst iterator...
235 template<class node_ty>
236 const ilist_iterator &operator=(const ilist_iterator<node_ty> &RHS) {
237 NodePtr = RHS.getNodePtrUnchecked();
242 operator pointer() const {
246 reference operator*() const {
249 pointer operator->() const { return &operator*(); }
251 // Comparison operators
252 bool operator==(const ilist_iterator &RHS) const {
253 return NodePtr == RHS.NodePtr;
255 bool operator!=(const ilist_iterator &RHS) const {
256 return NodePtr != RHS.NodePtr;
259 // Increment and decrement operators...
260 ilist_iterator &operator--() { // predecrement - Back up
261 NodePtr = Traits::getPrev(NodePtr);
262 assert(NodePtr && "--'d off the beginning of an ilist!");
265 ilist_iterator &operator++() { // preincrement - Advance
266 NodePtr = Traits::getNext(NodePtr);
269 ilist_iterator operator--(int) { // postdecrement operators...
270 ilist_iterator tmp = *this;
274 ilist_iterator operator++(int) { // postincrement operators...
275 ilist_iterator tmp = *this;
280 // Internal interface, do not use...
281 pointer getNodePtrUnchecked() const { return NodePtr; }
284 // These are to catch errors when people try to use them as random access
287 void operator-(int, ilist_iterator<T>) = delete;
289 void operator-(ilist_iterator<T>,int) = delete;
292 void operator+(int, ilist_iterator<T>) = delete;
294 void operator+(ilist_iterator<T>,int) = delete;
296 // operator!=/operator== - Allow mixed comparisons without dereferencing
297 // the iterator, which could very likely be pointing to end().
299 bool operator!=(const T* LHS, const ilist_iterator<const T> &RHS) {
300 return LHS != RHS.getNodePtrUnchecked();
303 bool operator==(const T* LHS, const ilist_iterator<const T> &RHS) {
304 return LHS == RHS.getNodePtrUnchecked();
307 bool operator!=(T* LHS, const ilist_iterator<T> &RHS) {
308 return LHS != RHS.getNodePtrUnchecked();
311 bool operator==(T* LHS, const ilist_iterator<T> &RHS) {
312 return LHS == RHS.getNodePtrUnchecked();
316 // Allow ilist_iterators to convert into pointers to a node automatically when
317 // used by the dyn_cast, cast, isa mechanisms...
319 template<typename From> struct simplify_type;
321 template<typename NodeTy> struct simplify_type<ilist_iterator<NodeTy> > {
322 typedef NodeTy* SimpleType;
324 static SimpleType getSimplifiedValue(ilist_iterator<NodeTy> &Node) {
328 template<typename NodeTy> struct simplify_type<const ilist_iterator<NodeTy> > {
329 typedef /*const*/ NodeTy* SimpleType;
331 static SimpleType getSimplifiedValue(const ilist_iterator<NodeTy> &Node) {
337 //===----------------------------------------------------------------------===//
339 /// iplist - The subset of list functionality that can safely be used on nodes
340 /// of polymorphic types, i.e. a heterogeneous list with a common base class that
341 /// holds the next/prev pointers. The only state of the list itself is a single
342 /// pointer to the head of the list.
344 /// This list can be in one of three interesting states:
345 /// 1. The list may be completely unconstructed. In this case, the head
346 /// pointer is null. When in this form, any query for an iterator (e.g.
347 /// begin() or end()) causes the list to transparently change to state #2.
348 /// 2. The list may be empty, but contain a sentinel for the end iterator. This
349 /// sentinel is created by the Traits::createSentinel method and is a link
350 /// in the list. When the list is empty, the pointer in the iplist points
351 /// to the sentinel. Once the sentinel is constructed, it
352 /// is not destroyed until the list is.
353 /// 3. The list may contain actual objects in it, which are stored as a doubly
354 /// linked list of nodes. One invariant of the list is that the predecessor
355 /// of the first node in the list always points to the last node in the list,
356 /// and the successor pointer for the sentinel (which always stays at the
357 /// end of the list) is always null.
359 template<typename NodeTy, typename Traits=ilist_traits<NodeTy> >
360 class iplist : public Traits {
361 mutable NodeTy *Head;
363 // Use the prev node pointer of 'head' as the tail pointer. This is really a
364 // circularly linked list where we snip the 'next' link from the sentinel node
365 // back to the first node in the list (to preserve assertions about going off
366 // the end of the list).
367 NodeTy *getTail() { return this->ensureHead(Head); }
368 const NodeTy *getTail() const { return this->ensureHead(Head); }
369 void setTail(NodeTy *N) const { this->noteHead(Head, N); }
371 /// CreateLazySentinel - This method verifies whether the sentinel for the
372 /// list has been created and lazily makes it if not.
373 void CreateLazySentinel() const {
374 this->ensureHead(Head);
377 static bool op_less(NodeTy &L, NodeTy &R) { return L < R; }
378 static bool op_equal(NodeTy &L, NodeTy &R) { return L == R; }
380 // No fundamental reason why iplist can't be copyable, but the default
381 // copy/copy-assign won't do.
382 iplist(const iplist &) = delete;
383 void operator=(const iplist &) = delete;
386 typedef NodeTy *pointer;
387 typedef const NodeTy *const_pointer;
388 typedef NodeTy &reference;
389 typedef const NodeTy &const_reference;
390 typedef NodeTy value_type;
391 typedef ilist_iterator<NodeTy> iterator;
392 typedef ilist_iterator<const NodeTy> const_iterator;
393 typedef size_t size_type;
394 typedef ptrdiff_t difference_type;
395 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
396 typedef std::reverse_iterator<iterator> reverse_iterator;
398 iplist() : Head(this->provideInitialHead()) {}
402 Traits::destroySentinel(getTail());
405 // Iterator creation methods.
407 CreateLazySentinel();
408 return iterator(Head);
410 const_iterator begin() const {
411 CreateLazySentinel();
412 return const_iterator(Head);
415 CreateLazySentinel();
416 return iterator(getTail());
418 const_iterator end() const {
419 CreateLazySentinel();
420 return const_iterator(getTail());
423 // reverse iterator creation methods.
424 reverse_iterator rbegin() { return reverse_iterator(end()); }
425 const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
426 reverse_iterator rend() { return reverse_iterator(begin()); }
427 const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
430 // Miscellaneous inspection routines.
431 size_type max_size() const { return size_type(-1); }
432 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
433 return !Head || Head == getTail();
436 // Front and back accessor functions...
438 assert(!empty() && "Called front() on empty list!");
441 const_reference front() const {
442 assert(!empty() && "Called front() on empty list!");
446 assert(!empty() && "Called back() on empty list!");
447 return *this->getPrev(getTail());
449 const_reference back() const {
450 assert(!empty() && "Called back() on empty list!");
451 return *this->getPrev(getTail());
454 void swap(iplist &RHS) {
455 assert(0 && "Swap does not use list traits callback correctly yet!");
456 std::swap(Head, RHS.Head);
459 iterator insert(iterator where, NodeTy *New) {
460 NodeTy *CurNode = where.getNodePtrUnchecked();
461 NodeTy *PrevNode = this->getPrev(CurNode);
462 this->setNext(New, CurNode);
463 this->setPrev(New, PrevNode);
465 if (CurNode != Head) // Is PrevNode off the beginning of the list?
466 this->setNext(PrevNode, New);
469 this->setPrev(CurNode, New);
471 this->addNodeToList(New); // Notify traits that we added a node...
475 iterator insertAfter(iterator where, NodeTy *New) {
477 return insert(begin(), New);
479 return insert(++where, New);
482 NodeTy *remove(iterator &IT) {
483 assert(IT != end() && "Cannot remove end of list!");
485 NodeTy *NextNode = this->getNext(Node);
486 NodeTy *PrevNode = this->getPrev(Node);
488 if (Node != Head) // Is PrevNode off the beginning of the list?
489 this->setNext(PrevNode, NextNode);
492 this->setPrev(NextNode, PrevNode);
494 this->removeNodeFromList(Node); // Notify traits that we removed a node...
496 // Set the next/prev pointers of the current node to null. This isn't
497 // strictly required, but this catches errors where a node is removed from
498 // an ilist (and potentially deleted) with iterators still pointing at it.
499 // When those iterators are incremented or decremented, they will assert on
500 // the null next/prev pointer instead of "usually working".
501 this->setNext(Node, nullptr);
502 this->setPrev(Node, nullptr);
506 NodeTy *remove(const iterator &IT) {
508 return remove(MutIt);
511 // erase - remove a node from the controlled sequence... and delete it.
512 iterator erase(iterator where) {
513 this->deleteNode(remove(where));
517 /// Remove all nodes from the list like clear(), but do not call
518 /// removeNodeFromList() or deleteNode().
520 /// This should only be used immediately before freeing nodes in bulk to
521 /// avoid traversing the list and bringing all the nodes into cache.
522 void clearAndLeakNodesUnsafely() {
525 this->setPrev(Head, Head);
530 // transfer - The heart of the splice function. Move linked list nodes from
531 // [first, last) into position.
533 void transfer(iterator position, iplist &L2, iterator first, iterator last) {
534 assert(first != last && "Should be checked by callers");
535 // Position cannot be contained in the range to be transferred.
536 // Check for the most common mistake.
537 assert(position != first &&
538 "Insertion point can't be one of the transferred nodes");
540 if (position != last) {
541 // Note: we have to be careful about the case when we move the first node
542 // in the list. This node is the list sentinel node and we can't move it.
543 NodeTy *ThisSentinel = getTail();
545 NodeTy *L2Sentinel = L2.getTail();
548 // Remove [first, last) from its old position.
549 NodeTy *First = &*first, *Prev = this->getPrev(First);
550 NodeTy *Next = last.getNodePtrUnchecked(), *Last = this->getPrev(Next);
552 this->setNext(Prev, Next);
555 this->setPrev(Next, Prev);
557 // Splice [first, last) into its new position.
558 NodeTy *PosNext = position.getNodePtrUnchecked();
559 NodeTy *PosPrev = this->getPrev(PosNext);
561 // Fix head of list...
563 this->setNext(PosPrev, First);
566 this->setPrev(First, PosPrev);
568 // Fix end of list...
569 this->setNext(Last, PosNext);
570 this->setPrev(PosNext, Last);
572 this->transferNodesFromList(L2, First, PosNext);
574 // Now that everything is set, restore the pointers to the list sentinels.
575 L2.setTail(L2Sentinel);
576 setTail(ThisSentinel);
582 //===----------------------------------------------------------------------===
583 // Functionality derived from other functions defined above...
586 size_type LLVM_ATTRIBUTE_UNUSED_RESULT size() const {
587 if (!Head) return 0; // Don't require construction of sentinel if empty.
588 return std::distance(begin(), end());
591 iterator erase(iterator first, iterator last) {
592 while (first != last)
593 first = erase(first);
597 void clear() { if (Head) erase(begin(), end()); }
599 // Front and back inserters...
600 void push_front(NodeTy *val) { insert(begin(), val); }
601 void push_back(NodeTy *val) { insert(end(), val); }
603 assert(!empty() && "pop_front() on empty list!");
607 assert(!empty() && "pop_back() on empty list!");
608 iterator t = end(); erase(--t);
611 // Special forms of insert...
612 template<class InIt> void insert(iterator where, InIt first, InIt last) {
613 for (; first != last; ++first) insert(where, *first);
616 // Splice members - defined in terms of transfer...
617 void splice(iterator where, iplist &L2) {
619 transfer(where, L2, L2.begin(), L2.end());
621 void splice(iterator where, iplist &L2, iterator first) {
622 iterator last = first; ++last;
623 if (where == first || where == last) return; // No change
624 transfer(where, L2, first, last);
626 void splice(iterator where, iplist &L2, iterator first, iterator last) {
627 if (first != last) transfer(where, L2, first, last);
630 template <class Compare>
631 void merge(iplist &Right, Compare comp) {
634 iterator First1 = begin(), Last1 = end();
635 iterator First2 = Right.begin(), Last2 = Right.end();
636 while (First1 != Last1 && First2 != Last2) {
637 if (comp(*First2, *First1)) {
638 iterator Next = First2;
639 transfer(First1, Right, First2, ++Next);
646 transfer(Last1, Right, First2, Last2);
648 void merge(iplist &Right) { return merge(Right, op_less); }
650 template <class Compare>
651 void sort(Compare comp) {
652 // The list is empty, vacuously sorted.
655 // The list has a single element, vacuously sorted.
656 if (std::next(begin()) == end())
658 // Find the split point for the list.
659 iterator Center = begin(), End = begin();
660 while (End != end() && std::next(End) != end()) {
661 Center = std::next(Center);
662 End = std::next(std::next(End));
664 // Split the list into two.
666 RightHalf.splice(RightHalf.begin(), *this, Center, end());
668 // Sort the two sublists.
670 RightHalf.sort(comp);
672 // Merge the two sublists back together.
673 merge(RightHalf, comp);
675 void sort() { sort(op_less); }
679 template<typename NodeTy>
680 struct ilist : public iplist<NodeTy> {
681 typedef typename iplist<NodeTy>::size_type size_type;
682 typedef typename iplist<NodeTy>::iterator iterator;
685 ilist(const ilist &right) {
686 insert(this->begin(), right.begin(), right.end());
688 explicit ilist(size_type count) {
689 insert(this->begin(), count, NodeTy());
691 ilist(size_type count, const NodeTy &val) {
692 insert(this->begin(), count, val);
694 template<class InIt> ilist(InIt first, InIt last) {
695 insert(this->begin(), first, last);
698 // bring hidden functions into scope
699 using iplist<NodeTy>::insert;
700 using iplist<NodeTy>::push_front;
701 using iplist<NodeTy>::push_back;
703 // Main implementation here - Insert for a node passed by value...
704 iterator insert(iterator where, const NodeTy &val) {
705 return insert(where, this->createNode(val));
709 // Front and back inserters...
710 void push_front(const NodeTy &val) { insert(this->begin(), val); }
711 void push_back(const NodeTy &val) { insert(this->end(), val); }
713 void insert(iterator where, size_type count, const NodeTy &val) {
714 for (; count != 0; --count) insert(where, val);
717 // Assign special forms...
718 void assign(size_type count, const NodeTy &val) {
719 iterator I = this->begin();
720 for (; I != this->end() && count != 0; ++I, --count)
723 insert(this->end(), val, val);
725 erase(I, this->end());
727 template<class InIt> void assign(InIt first1, InIt last1) {
728 iterator first2 = this->begin(), last2 = this->end();
729 for ( ; first1 != last1 && first2 != last2; ++first1, ++first2)
732 erase(first1, last1);
734 insert(last1, first2, last2);
739 void resize(size_type newsize, NodeTy val) {
740 iterator i = this->begin();
742 for ( ; i != this->end() && len < newsize; ++i, ++len) /* empty*/ ;
745 erase(i, this->end());
747 insert(this->end(), newsize - len, val);
749 void resize(size_type newsize) { resize(newsize, NodeTy()); }
752 } // End llvm namespace
755 // Ensure that swap uses the fast list swap...
757 void swap(llvm::iplist<Ty> &Left, llvm::iplist<Ty> &Right) {
760 } // End 'std' extensions...
762 #endif // LLVM_ADT_ILIST_H