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 // Iterator for intrusive list.
191 template <typename NodeTy>
193 : public std::iterator<std::bidirectional_iterator_tag, NodeTy, ptrdiff_t> {
195 typedef ilist_traits<NodeTy> Traits;
196 typedef std::iterator<std::bidirectional_iterator_tag, NodeTy, ptrdiff_t>
199 typedef typename super::value_type value_type;
200 typedef typename super::difference_type difference_type;
201 typedef typename super::pointer pointer;
202 typedef typename super::reference reference;
208 explicit ilist_iterator(pointer NP) : NodePtr(NP) {}
209 explicit ilist_iterator(reference NR) : NodePtr(&NR) {}
210 ilist_iterator() : NodePtr(nullptr) {}
212 // This is templated so that we can allow constructing a const iterator from
213 // a nonconst iterator...
214 template <class node_ty>
215 ilist_iterator(const ilist_iterator<node_ty> &RHS)
216 : NodePtr(RHS.getNodePtrUnchecked()) {}
218 // This is templated so that we can allow assigning to a const iterator from
219 // a nonconst iterator...
220 template <class node_ty>
221 const ilist_iterator &operator=(const ilist_iterator<node_ty> &RHS) {
222 NodePtr = RHS.getNodePtrUnchecked();
226 void reset(pointer NP) { NodePtr = NP; }
229 explicit operator pointer() const { return NodePtr; }
230 reference operator*() const { return *NodePtr; }
231 pointer operator->() const { return &operator*(); }
233 // Comparison operators
234 template <class Y> bool operator==(const ilist_iterator<Y> &RHS) const {
235 return NodePtr == RHS.getNodePtrUnchecked();
237 template <class Y> bool operator!=(const ilist_iterator<Y> &RHS) const {
238 return NodePtr != RHS.getNodePtrUnchecked();
241 // Increment and decrement operators...
242 ilist_iterator &operator--() {
243 NodePtr = Traits::getPrev(NodePtr);
244 assert(NodePtr && "--'d off the beginning of an ilist!");
247 ilist_iterator &operator++() {
248 NodePtr = Traits::getNext(NodePtr);
251 ilist_iterator operator--(int) {
252 ilist_iterator tmp = *this;
256 ilist_iterator operator++(int) {
257 ilist_iterator tmp = *this;
262 // Internal interface, do not use...
263 pointer getNodePtrUnchecked() const { return NodePtr; }
266 // Allow ilist_iterators to convert into pointers to a node automatically when
267 // used by the dyn_cast, cast, isa mechanisms...
269 template<typename From> struct simplify_type;
271 template<typename NodeTy> struct simplify_type<ilist_iterator<NodeTy> > {
272 typedef NodeTy* SimpleType;
274 static SimpleType getSimplifiedValue(ilist_iterator<NodeTy> &Node) {
278 template<typename NodeTy> struct simplify_type<const ilist_iterator<NodeTy> > {
279 typedef /*const*/ NodeTy* SimpleType;
281 static SimpleType getSimplifiedValue(const ilist_iterator<NodeTy> &Node) {
287 //===----------------------------------------------------------------------===//
289 /// iplist - The subset of list functionality that can safely be used on nodes
290 /// of polymorphic types, i.e. a heterogeneous list with a common base class that
291 /// holds the next/prev pointers. The only state of the list itself is a single
292 /// pointer to the head of the list.
294 /// This list can be in one of three interesting states:
295 /// 1. The list may be completely unconstructed. In this case, the head
296 /// pointer is null. When in this form, any query for an iterator (e.g.
297 /// begin() or end()) causes the list to transparently change to state #2.
298 /// 2. The list may be empty, but contain a sentinel for the end iterator. This
299 /// sentinel is created by the Traits::createSentinel method and is a link
300 /// in the list. When the list is empty, the pointer in the iplist points
301 /// to the sentinel. Once the sentinel is constructed, it
302 /// is not destroyed until the list is.
303 /// 3. The list may contain actual objects in it, which are stored as a doubly
304 /// linked list of nodes. One invariant of the list is that the predecessor
305 /// of the first node in the list always points to the last node in the list,
306 /// and the successor pointer for the sentinel (which always stays at the
307 /// end of the list) is always null.
309 template<typename NodeTy, typename Traits=ilist_traits<NodeTy> >
310 class iplist : public Traits {
311 mutable NodeTy *Head;
313 // Use the prev node pointer of 'head' as the tail pointer. This is really a
314 // circularly linked list where we snip the 'next' link from the sentinel node
315 // back to the first node in the list (to preserve assertions about going off
316 // the end of the list).
317 NodeTy *getTail() { return this->ensureHead(Head); }
318 const NodeTy *getTail() const { return this->ensureHead(Head); }
319 void setTail(NodeTy *N) const { this->noteHead(Head, N); }
321 /// CreateLazySentinel - This method verifies whether the sentinel for the
322 /// list has been created and lazily makes it if not.
323 void CreateLazySentinel() const {
324 this->ensureHead(Head);
327 static bool op_less(NodeTy &L, NodeTy &R) { return L < R; }
328 static bool op_equal(NodeTy &L, NodeTy &R) { return L == R; }
330 // No fundamental reason why iplist can't be copyable, but the default
331 // copy/copy-assign won't do.
332 iplist(const iplist &) = delete;
333 void operator=(const iplist &) = delete;
336 typedef NodeTy *pointer;
337 typedef const NodeTy *const_pointer;
338 typedef NodeTy &reference;
339 typedef const NodeTy &const_reference;
340 typedef NodeTy value_type;
341 typedef ilist_iterator<NodeTy> iterator;
342 typedef ilist_iterator<const NodeTy> const_iterator;
343 typedef size_t size_type;
344 typedef ptrdiff_t difference_type;
345 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
346 typedef std::reverse_iterator<iterator> reverse_iterator;
348 iplist() : Head(this->provideInitialHead()) {}
352 Traits::destroySentinel(getTail());
355 // Iterator creation methods.
357 CreateLazySentinel();
358 return iterator(Head);
360 const_iterator begin() const {
361 CreateLazySentinel();
362 return const_iterator(Head);
365 CreateLazySentinel();
366 return iterator(getTail());
368 const_iterator end() const {
369 CreateLazySentinel();
370 return const_iterator(getTail());
373 // reverse iterator creation methods.
374 reverse_iterator rbegin() { return reverse_iterator(end()); }
375 const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
376 reverse_iterator rend() { return reverse_iterator(begin()); }
377 const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
380 // Miscellaneous inspection routines.
381 size_type max_size() const { return size_type(-1); }
382 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
383 return !Head || Head == getTail();
386 // Front and back accessor functions...
388 assert(!empty() && "Called front() on empty list!");
391 const_reference front() const {
392 assert(!empty() && "Called front() on empty list!");
396 assert(!empty() && "Called back() on empty list!");
397 return *this->getPrev(getTail());
399 const_reference back() const {
400 assert(!empty() && "Called back() on empty list!");
401 return *this->getPrev(getTail());
404 void swap(iplist &RHS) {
405 assert(0 && "Swap does not use list traits callback correctly yet!");
406 std::swap(Head, RHS.Head);
409 iterator insert(iterator where, NodeTy *New) {
410 NodeTy *CurNode = where.getNodePtrUnchecked();
411 NodeTy *PrevNode = this->getPrev(CurNode);
412 this->setNext(New, CurNode);
413 this->setPrev(New, PrevNode);
415 if (CurNode != Head) // Is PrevNode off the beginning of the list?
416 this->setNext(PrevNode, New);
419 this->setPrev(CurNode, New);
421 this->addNodeToList(New); // Notify traits that we added a node...
422 return iterator(New);
425 iterator insert(iterator where, const NodeTy &New) {
426 return this->insert(where, new NodeTy(New));
429 iterator insertAfter(iterator where, NodeTy *New) {
431 return insert(begin(), New);
433 return insert(++where, New);
436 NodeTy *remove(iterator &IT) {
437 assert(IT != end() && "Cannot remove end of list!");
439 NodeTy *NextNode = this->getNext(Node);
440 NodeTy *PrevNode = this->getPrev(Node);
442 if (Node != Head) // Is PrevNode off the beginning of the list?
443 this->setNext(PrevNode, NextNode);
446 this->setPrev(NextNode, PrevNode);
448 this->removeNodeFromList(Node); // Notify traits that we removed a node...
450 // Set the next/prev pointers of the current node to null. This isn't
451 // strictly required, but this catches errors where a node is removed from
452 // an ilist (and potentially deleted) with iterators still pointing at it.
453 // When those iterators are incremented or decremented, they will assert on
454 // the null next/prev pointer instead of "usually working".
455 this->setNext(Node, nullptr);
456 this->setPrev(Node, nullptr);
460 NodeTy *remove(const iterator &IT) {
462 return remove(MutIt);
465 NodeTy *remove(NodeTy *IT) { return remove(iterator(IT)); }
466 NodeTy *remove(NodeTy &IT) { return remove(iterator(IT)); }
468 // erase - remove a node from the controlled sequence... and delete it.
469 iterator erase(iterator where) {
470 this->deleteNode(remove(where));
474 iterator erase(NodeTy *IT) { return erase(iterator(IT)); }
475 iterator erase(NodeTy &IT) { return erase(iterator(IT)); }
477 /// Remove all nodes from the list like clear(), but do not call
478 /// removeNodeFromList() or deleteNode().
480 /// This should only be used immediately before freeing nodes in bulk to
481 /// avoid traversing the list and bringing all the nodes into cache.
482 void clearAndLeakNodesUnsafely() {
485 this->setPrev(Head, Head);
490 // transfer - The heart of the splice function. Move linked list nodes from
491 // [first, last) into position.
493 void transfer(iterator position, iplist &L2, iterator first, iterator last) {
494 assert(first != last && "Should be checked by callers");
495 // Position cannot be contained in the range to be transferred.
496 // Check for the most common mistake.
497 assert(position != first &&
498 "Insertion point can't be one of the transferred nodes");
500 if (position != last) {
501 // Note: we have to be careful about the case when we move the first node
502 // in the list. This node is the list sentinel node and we can't move it.
503 NodeTy *ThisSentinel = getTail();
505 NodeTy *L2Sentinel = L2.getTail();
508 // Remove [first, last) from its old position.
509 NodeTy *First = &*first, *Prev = this->getPrev(First);
510 NodeTy *Next = last.getNodePtrUnchecked(), *Last = this->getPrev(Next);
512 this->setNext(Prev, Next);
515 this->setPrev(Next, Prev);
517 // Splice [first, last) into its new position.
518 NodeTy *PosNext = position.getNodePtrUnchecked();
519 NodeTy *PosPrev = this->getPrev(PosNext);
521 // Fix head of list...
523 this->setNext(PosPrev, First);
526 this->setPrev(First, PosPrev);
528 // Fix end of list...
529 this->setNext(Last, PosNext);
530 this->setPrev(PosNext, Last);
532 this->transferNodesFromList(L2, iterator(First), iterator(PosNext));
534 // Now that everything is set, restore the pointers to the list sentinels.
535 L2.setTail(L2Sentinel);
536 setTail(ThisSentinel);
542 //===----------------------------------------------------------------------===
543 // Functionality derived from other functions defined above...
546 size_type LLVM_ATTRIBUTE_UNUSED_RESULT size() const {
547 if (!Head) return 0; // Don't require construction of sentinel if empty.
548 return std::distance(begin(), end());
551 iterator erase(iterator first, iterator last) {
552 while (first != last)
553 first = erase(first);
557 void clear() { if (Head) erase(begin(), end()); }
559 // Front and back inserters...
560 void push_front(NodeTy *val) { insert(begin(), val); }
561 void push_back(NodeTy *val) { insert(end(), val); }
563 assert(!empty() && "pop_front() on empty list!");
567 assert(!empty() && "pop_back() on empty list!");
568 iterator t = end(); erase(--t);
571 // Special forms of insert...
572 template<class InIt> void insert(iterator where, InIt first, InIt last) {
573 for (; first != last; ++first) insert(where, *first);
576 // Splice members - defined in terms of transfer...
577 void splice(iterator where, iplist &L2) {
579 transfer(where, L2, L2.begin(), L2.end());
581 void splice(iterator where, iplist &L2, iterator first) {
582 iterator last = first; ++last;
583 if (where == first || where == last) return; // No change
584 transfer(where, L2, first, last);
586 void splice(iterator where, iplist &L2, iterator first, iterator last) {
587 if (first != last) transfer(where, L2, first, last);
589 void splice(iterator where, iplist &L2, NodeTy &N) {
590 splice(where, L2, iterator(N));
592 void splice(iterator where, iplist &L2, NodeTy *N) {
593 splice(where, L2, iterator(N));
596 template <class Compare>
597 void merge(iplist &Right, Compare comp) {
600 iterator First1 = begin(), Last1 = end();
601 iterator First2 = Right.begin(), Last2 = Right.end();
602 while (First1 != Last1 && First2 != Last2) {
603 if (comp(*First2, *First1)) {
604 iterator Next = First2;
605 transfer(First1, Right, First2, ++Next);
612 transfer(Last1, Right, First2, Last2);
614 void merge(iplist &Right) { return merge(Right, op_less); }
616 template <class Compare>
617 void sort(Compare comp) {
618 // The list is empty, vacuously sorted.
621 // The list has a single element, vacuously sorted.
622 if (std::next(begin()) == end())
624 // Find the split point for the list.
625 iterator Center = begin(), End = begin();
626 while (End != end() && std::next(End) != end()) {
627 Center = std::next(Center);
628 End = std::next(std::next(End));
630 // Split the list into two.
632 RightHalf.splice(RightHalf.begin(), *this, Center, end());
634 // Sort the two sublists.
636 RightHalf.sort(comp);
638 // Merge the two sublists back together.
639 merge(RightHalf, comp);
641 void sort() { sort(op_less); }
643 /// \brief Get the previous node, or \c nullptr for the list head.
644 NodeTy *getPrevNode(NodeTy &N) const {
645 auto I = N.getIterator();
648 return &*std::prev(I);
650 /// \brief Get the previous node, or \c nullptr for the list head.
651 const NodeTy *getPrevNode(const NodeTy &N) const {
652 return getPrevNode(const_cast<NodeTy &>(N));
655 /// \brief Get the next node, or \c nullptr for the list tail.
656 NodeTy *getNextNode(NodeTy &N) const {
657 auto Next = std::next(N.getIterator());
662 /// \brief Get the next node, or \c nullptr for the list tail.
663 const NodeTy *getNextNode(const NodeTy &N) const {
664 return getNextNode(const_cast<NodeTy &>(N));
669 template<typename NodeTy>
670 struct ilist : public iplist<NodeTy> {
671 typedef typename iplist<NodeTy>::size_type size_type;
672 typedef typename iplist<NodeTy>::iterator iterator;
675 ilist(const ilist &right) : iplist<NodeTy>() {
676 insert(this->begin(), right.begin(), right.end());
678 explicit ilist(size_type count) {
679 insert(this->begin(), count, NodeTy());
681 ilist(size_type count, const NodeTy &val) {
682 insert(this->begin(), count, val);
684 template<class InIt> ilist(InIt first, InIt last) {
685 insert(this->begin(), first, last);
688 // bring hidden functions into scope
689 using iplist<NodeTy>::insert;
690 using iplist<NodeTy>::push_front;
691 using iplist<NodeTy>::push_back;
693 // Main implementation here - Insert for a node passed by value...
694 iterator insert(iterator where, const NodeTy &val) {
695 return insert(where, this->createNode(val));
699 // Front and back inserters...
700 void push_front(const NodeTy &val) { insert(this->begin(), val); }
701 void push_back(const NodeTy &val) { insert(this->end(), val); }
703 void insert(iterator where, size_type count, const NodeTy &val) {
704 for (; count != 0; --count) insert(where, val);
707 // Assign special forms...
708 void assign(size_type count, const NodeTy &val) {
709 iterator I = this->begin();
710 for (; I != this->end() && count != 0; ++I, --count)
713 insert(this->end(), val, val);
715 erase(I, this->end());
717 template<class InIt> void assign(InIt first1, InIt last1) {
718 iterator first2 = this->begin(), last2 = this->end();
719 for ( ; first1 != last1 && first2 != last2; ++first1, ++first2)
722 erase(first1, last1);
724 insert(last1, first2, last2);
729 void resize(size_type newsize, NodeTy val) {
730 iterator i = this->begin();
732 for ( ; i != this->end() && len < newsize; ++i, ++len) /* empty*/ ;
735 erase(i, this->end());
737 insert(this->end(), newsize - len, val);
739 void resize(size_type newsize) { resize(newsize, NodeTy()); }
742 } // End llvm namespace
745 // Ensure that swap uses the fast list swap...
747 void swap(llvm::iplist<Ty> &Left, llvm::iplist<Ty> &Right) {
750 } // End 'std' extensions...
752 #endif // LLVM_ADT_ILIST_H