1 //===- llvm/ADT/ilist_node.h - Intrusive Linked List Helper -----*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// This file defines the ilist_node class template, which is a convenient
11 /// base class for creating classes that can be used with ilists.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_ADT_ILIST_NODE_H
16 #define LLVM_ADT_ILIST_NODE_H
17 
18 #include "llvm/ADT/ilist_node_base.h"
19 #include "llvm/ADT/ilist_node_options.h"
20 
21 namespace llvm {
22 
23 namespace ilist_detail {
24 
25 struct NodeAccess;
26 
27 } // end namespace ilist_detail
28 
29 template <class OptionsT, bool IsReverse, bool IsConst> class ilist_iterator;
30 template <class OptionsT> class ilist_sentinel;
31 
32 /// Implementation for an ilist node.
33 ///
34 /// Templated on an appropriate \a ilist_detail::node_options, usually computed
35 /// by \a ilist_detail::compute_node_options.
36 ///
37 /// This is a wrapper around \a ilist_node_base whose main purpose is to
38 /// provide type safety: you can't insert nodes of \a ilist_node_impl into the
39 /// wrong \a simple_ilist or \a iplist.
40 template <class OptionsT> class ilist_node_impl : OptionsT::node_base_type {
41   using value_type = typename OptionsT::value_type;
42   using node_base_type = typename OptionsT::node_base_type;
43   using list_base_type = typename OptionsT::list_base_type;
44 
45   friend typename OptionsT::list_base_type;
46   friend struct ilist_detail::NodeAccess;
47   friend class ilist_sentinel<OptionsT>;
48   friend class ilist_iterator<OptionsT, false, false>;
49   friend class ilist_iterator<OptionsT, false, true>;
50   friend class ilist_iterator<OptionsT, true, false>;
51   friend class ilist_iterator<OptionsT, true, true>;
52 
53 protected:
54   using self_iterator = ilist_iterator<OptionsT, false, false>;
55   using const_self_iterator = ilist_iterator<OptionsT, false, true>;
56   using reverse_self_iterator = ilist_iterator<OptionsT, true, false>;
57   using const_reverse_self_iterator = ilist_iterator<OptionsT, true, true>;
58 
59   ilist_node_impl() = default;
60 
61 private:
62   ilist_node_impl *getPrev() {
63     return static_cast<ilist_node_impl *>(node_base_type::getPrev());
64   }
65 
66   ilist_node_impl *getNext() {
67     return static_cast<ilist_node_impl *>(node_base_type::getNext());
68   }
69 
70   const ilist_node_impl *getPrev() const {
71     return static_cast<ilist_node_impl *>(node_base_type::getPrev());
72   }
73 
74   const ilist_node_impl *getNext() const {
75     return static_cast<ilist_node_impl *>(node_base_type::getNext());
76   }
77 
78   void setPrev(ilist_node_impl *N) { node_base_type::setPrev(N); }
79   void setNext(ilist_node_impl *N) { node_base_type::setNext(N); }
80 
81 public:
82   self_iterator getIterator() { return self_iterator(*this); }
83   const_self_iterator getIterator() const { return const_self_iterator(*this); }
84 
85   reverse_self_iterator getReverseIterator() {
86     return reverse_self_iterator(*this);
87   }
88 
89   const_reverse_self_iterator getReverseIterator() const {
90     return const_reverse_self_iterator(*this);
91   }
92 
93   // Under-approximation, but always available for assertions.
94   using node_base_type::isKnownSentinel;
95 
96   /// Check whether this is the sentinel node.
97   ///
98   /// This requires sentinel tracking to be explicitly enabled.  Use the
99   /// ilist_sentinel_tracking<true> option to get this API.
100   bool isSentinel() const {
101     static_assert(OptionsT::is_sentinel_tracking_explicit,
102                   "Use ilist_sentinel_tracking<true> to enable isSentinel()");
103     return node_base_type::isSentinel();
104   }
105 };
106 
107 /// An intrusive list node.
108 ///
109 /// A base class to enable membership in intrusive lists, including \a
110 /// simple_ilist, \a iplist, and \a ilist.  The first template parameter is the
111 /// \a value_type for the list.
112 ///
113 /// An ilist node can be configured with compile-time options to change
114 /// behaviour and/or add API.
115 ///
116 /// By default, an \a ilist_node knows whether it is the list sentinel (an
117 /// instance of \a ilist_sentinel) if and only if
118 /// LLVM_ENABLE_ABI_BREAKING_CHECKS.  The function \a isKnownSentinel() always
119 /// returns \c false tracking is off.  Sentinel tracking steals a bit from the
120 /// "prev" link, which adds a mask operation when decrementing an iterator, but
121 /// enables bug-finding assertions in \a ilist_iterator.
122 ///
123 /// To turn sentinel tracking on all the time, pass in the
124 /// ilist_sentinel_tracking<true> template parameter.  This also enables the \a
125 /// isSentinel() function.  The same option must be passed to the intrusive
126 /// list.  (ilist_sentinel_tracking<false> turns sentinel tracking off all the
127 /// time.)
128 ///
129 /// A type can inherit from ilist_node multiple times by passing in different
130 /// \a ilist_tag options.  This allows a single instance to be inserted into
131 /// multiple lists simultaneously, where each list is given the same tag.
132 ///
133 /// \example
134 /// struct A {};
135 /// struct B {};
136 /// struct N : ilist_node<N, ilist_tag<A>>, ilist_node<N, ilist_tag<B>> {};
137 ///
138 /// void foo() {
139 ///   simple_ilist<N, ilist_tag<A>> ListA;
140 ///   simple_ilist<N, ilist_tag<B>> ListB;
141 ///   N N1;
142 ///   ListA.push_back(N1);
143 ///   ListB.push_back(N1);
144 /// }
145 /// \endexample
146 ///
147 /// See \a is_valid_option for steps on adding a new option.
148 template <class T, class... Options>
149 class ilist_node
150     : public ilist_node_impl<
151           typename ilist_detail::compute_node_options<T, Options...>::type> {
152   static_assert(ilist_detail::check_options<Options...>::value,
153                 "Unrecognized node option!");
154 };
155 
156 namespace ilist_detail {
157 
158 /// An access class for ilist_node private API.
159 ///
160 /// This gives access to the private parts of ilist nodes.  Nodes for an ilist
161 /// should friend this class if they inherit privately from ilist_node.
162 ///
163 /// Using this class outside of the ilist implementation is unsupported.
164 struct NodeAccess {
165 protected:
166   template <class OptionsT>
167   static ilist_node_impl<OptionsT> *getNodePtr(typename OptionsT::pointer N) {
168     return N;
169   }
170 
171   template <class OptionsT>
172   static const ilist_node_impl<OptionsT> *
173   getNodePtr(typename OptionsT::const_pointer N) {
174     return N;
175   }
176 
177   template <class OptionsT>
178   static typename OptionsT::pointer getValuePtr(ilist_node_impl<OptionsT> *N) {
179     return static_cast<typename OptionsT::pointer>(N);
180   }
181 
182   template <class OptionsT>
183   static typename OptionsT::const_pointer
184   getValuePtr(const ilist_node_impl<OptionsT> *N) {
185     return static_cast<typename OptionsT::const_pointer>(N);
186   }
187 
188   template <class OptionsT>
189   static ilist_node_impl<OptionsT> *getPrev(ilist_node_impl<OptionsT> &N) {
190     return N.getPrev();
191   }
192 
193   template <class OptionsT>
194   static ilist_node_impl<OptionsT> *getNext(ilist_node_impl<OptionsT> &N) {
195     return N.getNext();
196   }
197 
198   template <class OptionsT>
199   static const ilist_node_impl<OptionsT> *
200   getPrev(const ilist_node_impl<OptionsT> &N) {
201     return N.getPrev();
202   }
203 
204   template <class OptionsT>
205   static const ilist_node_impl<OptionsT> *
206   getNext(const ilist_node_impl<OptionsT> &N) {
207     return N.getNext();
208   }
209 };
210 
211 template <class OptionsT> struct SpecificNodeAccess : NodeAccess {
212 protected:
213   using pointer = typename OptionsT::pointer;
214   using const_pointer = typename OptionsT::const_pointer;
215   using node_type = ilist_node_impl<OptionsT>;
216 
217   static node_type *getNodePtr(pointer N) {
218     return NodeAccess::getNodePtr<OptionsT>(N);
219   }
220 
221   static const node_type *getNodePtr(const_pointer N) {
222     return NodeAccess::getNodePtr<OptionsT>(N);
223   }
224 
225   static pointer getValuePtr(node_type *N) {
226     return NodeAccess::getValuePtr<OptionsT>(N);
227   }
228 
229   static const_pointer getValuePtr(const node_type *N) {
230     return NodeAccess::getValuePtr<OptionsT>(N);
231   }
232 };
233 
234 } // end namespace ilist_detail
235 
236 template <class OptionsT>
237 class ilist_sentinel : public ilist_node_impl<OptionsT> {
238 public:
239   ilist_sentinel() {
240     this->initializeSentinel();
241     reset();
242   }
243 
244   void reset() {
245     this->setPrev(this);
246     this->setNext(this);
247   }
248 
249   bool empty() const { return this == this->getPrev(); }
250 };
251 
252 /// An ilist node that can access its parent list.
253 ///
254 /// Requires \c NodeTy to have \a getParent() to find the parent node, and the
255 /// \c ParentTy to have \a getSublistAccess() to get a reference to the list.
256 template <typename NodeTy, typename ParentTy, class... Options>
257 class ilist_node_with_parent : public ilist_node<NodeTy, Options...> {
258 protected:
259   ilist_node_with_parent() = default;
260 
261 private:
262   /// Forward to NodeTy::getParent().
263   ///
264   /// Note: do not use the name "getParent()".  We want a compile error
265   /// (instead of recursion) when the subclass fails to implement \a
266   /// getParent().
267   const ParentTy *getNodeParent() const {
268     return static_cast<const NodeTy *>(this)->getParent();
269   }
270 
271 public:
272   /// @name Adjacent Node Accessors
273   /// @{
274   /// Get the previous node, or \c nullptr for the list head.
275   NodeTy *getPrevNode() {
276     // Should be separated to a reused function, but then we couldn't use auto
277     // (and would need the type of the list).
278     const auto &List =
279         getNodeParent()->*(ParentTy::getSublistAccess((NodeTy *)nullptr));
280     return List.getPrevNode(*static_cast<NodeTy *>(this));
281   }
282 
283   /// Get the previous node, or \c nullptr for the list head.
284   const NodeTy *getPrevNode() const {
285     return const_cast<ilist_node_with_parent *>(this)->getPrevNode();
286   }
287 
288   /// Get the next node, or \c nullptr for the list tail.
289   NodeTy *getNextNode() {
290     // Should be separated to a reused function, but then we couldn't use auto
291     // (and would need the type of the list).
292     const auto &List =
293         getNodeParent()->*(ParentTy::getSublistAccess((NodeTy *)nullptr));
294     return List.getNextNode(*static_cast<NodeTy *>(this));
295   }
296 
297   /// Get the next node, or \c nullptr for the list tail.
298   const NodeTy *getNextNode() const {
299     return const_cast<ilist_node_with_parent *>(this)->getNextNode();
300   }
301   /// @}
302 };
303 
304 } // end namespace llvm
305 
306 #endif // LLVM_ADT_ILIST_NODE_H
307