1//===- llvm/ADT/simple_ilist.h - Simple Intrusive List ----------*- 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#ifndef LLVM_ADT_SIMPLE_ILIST_H
10#define LLVM_ADT_SIMPLE_ILIST_H
11
12#include "llvm/ADT/ilist_base.h"
13#include "llvm/ADT/ilist_iterator.h"
14#include "llvm/ADT/ilist_node.h"
15#include "llvm/ADT/ilist_node_options.h"
16#include "llvm/Support/Compiler.h"
17#include <algorithm>
18#include <cassert>
19#include <cstddef>
20#include <functional>
21#include <iterator>
22#include <utility>
23
24namespace llvm {
25
26/// A simple intrusive list implementation.
27///
28/// This is a simple intrusive list for a \c T that inherits from \c
29/// ilist_node<T>. The list never takes ownership of anything inserted in it.
30///
31/// Unlike \a iplist<T> and \a ilist<T>, \a simple_ilist<T> never deletes
32/// values, and has no callback traits.
33///
34/// The API for adding nodes include \a push_front(), \a push_back(), and \a
35/// insert(). These all take values by reference (not by pointer), except for
36/// the range version of \a insert().
37///
38/// There are three sets of API for discarding nodes from the list: \a
39/// remove(), which takes a reference to the node to remove, \a erase(), which
40/// takes an iterator or iterator range and returns the next one, and \a
41/// clear(), which empties out the container. All three are constant time
42/// operations. None of these deletes any nodes; in particular, if there is a
43/// single node in the list, then these have identical semantics:
44/// \li \c L.remove(L.front());
45/// \li \c L.erase(L.begin());
46/// \li \c L.clear();
47///
48/// As a convenience for callers, there are parallel APIs that take a \c
49/// Disposer (such as \c std::default_delete<T>): \a removeAndDispose(), \a
50/// eraseAndDispose(), and \a clearAndDispose(). These have different names
51/// because the extra semantic is otherwise non-obvious. They are equivalent
52/// to calling \a std::for_each() on the range to be discarded.
53///
54/// The currently available \p Options customize the nodes in the list. The
55/// same options must be specified in the \a ilist_node instantiation for
56/// compatibility (although the order is irrelevant).
57/// \li Use \a ilist_tag to designate which ilist_node for a given \p T this
58/// list should use. This is useful if a type \p T is part of multiple,
59/// independent lists simultaneously.
60/// \li Use \a ilist_sentinel_tracking to always (or never) track whether a
61/// node is a sentinel. Specifying \c true enables the \a
62/// ilist_node::isSentinel() API. Unlike \a ilist_node::isKnownSentinel(),
63/// which is only appropriate for assertions, \a ilist_node::isSentinel() is
64/// appropriate for real logic.
65///
66/// Here are examples of \p Options usage:
67/// \li \c simple_ilist<T> gives the defaults. \li \c
68/// simple_ilist<T,ilist_sentinel_tracking<true>> enables the \a
69/// ilist_node::isSentinel() API.
70/// \li \c simple_ilist<T,ilist_tag<A>,ilist_sentinel_tracking<false>>
71/// specifies a tag of A and that tracking should be off (even when
72/// LLVM_ENABLE_ABI_BREAKING_CHECKS are enabled).
73/// \li \c simple_ilist<T,ilist_sentinel_tracking<false>,ilist_tag<A>> is
74/// equivalent to the last.
75///
76/// See \a is_valid_option for steps on adding a new option.
77template <typename T, class... Options>
78class simple_ilist
79 : ilist_detail::compute_node_options<T, Options...>::type::list_base_type,
80 ilist_detail::SpecificNodeAccess<
81 typename ilist_detail::compute_node_options<T, Options...>::type> {
82 static_assert(ilist_detail::check_options<Options...>::value,
83 "Unrecognized node option!");
84 using OptionsT =
85 typename ilist_detail::compute_node_options<T, Options...>::type;
86 using list_base_type = typename OptionsT::list_base_type;
87 ilist_sentinel<OptionsT> Sentinel;
88
89public:
90 using value_type = typename OptionsT::value_type;
91 using pointer = typename OptionsT::pointer;
92 using reference = typename OptionsT::reference;
93 using const_pointer = typename OptionsT::const_pointer;
94 using const_reference = typename OptionsT::const_reference;
95 using iterator = ilist_iterator<OptionsT, false, false>;
96 using const_iterator = ilist_iterator<OptionsT, false, true>;
97 using reverse_iterator = ilist_iterator<OptionsT, true, false>;
98 using const_reverse_iterator = ilist_iterator<OptionsT, true, true>;
99 using size_type = size_t;
100 using difference_type = ptrdiff_t;
101
102 simple_ilist() = default;
103 ~simple_ilist() = default;
104
105 // No copy constructors.
106 simple_ilist(const simple_ilist &) = delete;
107 simple_ilist &operator=(const simple_ilist &) = delete;
108
109 // Move constructors.
110 simple_ilist(simple_ilist &&X) { splice(end(), X); }
111 simple_ilist &operator=(simple_ilist &&X) {
112 clear();
113 splice(end(), X);
114 return *this;
115 }
116
117 iterator begin() { return ++iterator(Sentinel); }
118 const_iterator begin() const { return ++const_iterator(Sentinel); }
119 iterator end() { return iterator(Sentinel); }
120 const_iterator end() const { return const_iterator(Sentinel); }
121 reverse_iterator rbegin() { return ++reverse_iterator(Sentinel); }
122 const_reverse_iterator rbegin() const {
123 return ++const_reverse_iterator(Sentinel);
124 }
125 reverse_iterator rend() { return reverse_iterator(Sentinel); }
126 const_reverse_iterator rend() const {
127 return const_reverse_iterator(Sentinel);
128 }
129
130 /// Check if the list is empty in constant time.
131 LLVM_NODISCARD bool empty() const { return Sentinel.empty(); }
132
133 /// Calculate the size of the list in linear time.
134 LLVM_NODISCARD size_type size() const {
135 return std::distance(begin(), end());
136 }
137
138 reference front() { return *begin(); }
139 const_reference front() const { return *begin(); }
140 reference back() { return *rbegin(); }
141 const_reference back() const { return *rbegin(); }
142
143 /// Insert a node at the front; never copies.
144 void push_front(reference Node) { insert(begin(), Node); }
145
146 /// Insert a node at the back; never copies.
147 void push_back(reference Node) { insert(end(), Node); }
148
149 /// Remove the node at the front; never deletes.
150 void pop_front() { erase(begin()); }
151
152 /// Remove the node at the back; never deletes.
153 void pop_back() { erase(--end()); }
154
155 /// Swap with another list in place using std::swap.
156 void swap(simple_ilist &X) { std::swap(*this, X); }
157
158 /// Insert a node by reference; never copies.
159 iterator insert(iterator I, reference Node) {
160 list_base_type::insertBefore(*I.getNodePtr(), *this->getNodePtr(&Node));
161 return iterator(&Node);
162 }
163
164 /// Insert a range of nodes; never copies.
165 template <class Iterator>
166 void insert(iterator I, Iterator First, Iterator Last) {
167 for (; First != Last; ++First)
168 insert(I, *First);
169 }
170
171 /// Clone another list.
172 template <class Cloner, class Disposer>
173 void cloneFrom(const simple_ilist &L2, Cloner clone, Disposer dispose) {
174 clearAndDispose(dispose);
175 for (const_reference V : L2)
176 push_back(*clone(V));
177 }
178
179 /// Remove a node by reference; never deletes.
180 ///
181 /// \see \a erase() for removing by iterator.
182 /// \see \a removeAndDispose() if the node should be deleted.
183 void remove(reference N) { list_base_type::remove(*this->getNodePtr(&N)); }
184
185 /// Remove a node by reference and dispose of it.
186 template <class Disposer>
187 void removeAndDispose(reference N, Disposer dispose) {
188 remove(N);
189 dispose(&N);
190 }
191
192 /// Remove a node by iterator; never deletes.
193 ///
194 /// \see \a remove() for removing by reference.
195 /// \see \a eraseAndDispose() it the node should be deleted.
196 iterator erase(iterator I) {
197 assert(I != end() && "Cannot remove end of list!");
198 remove(*I++);
199 return I;
200 }
201
202 /// Remove a range of nodes; never deletes.
203 ///
204 /// \see \a eraseAndDispose() if the nodes should be deleted.
205 iterator erase(iterator First, iterator Last) {
206 list_base_type::removeRange(*First.getNodePtr(), *Last.getNodePtr());
207 return Last;
208 }
209
210 /// Remove a node by iterator and dispose of it.
211 template <class Disposer>
212 iterator eraseAndDispose(iterator I, Disposer dispose) {
213 auto Next = std::next(I);
214 erase(I);
215 dispose(&*I);
216 return Next;
217 }
218
219 /// Remove a range of nodes and dispose of them.
220 template <class Disposer>
221 iterator eraseAndDispose(iterator First, iterator Last, Disposer dispose) {
222 while (First != Last)
223 First = eraseAndDispose(First, dispose);
224 return Last;
225 }
226
227 /// Clear the list; never deletes.
228 ///
229 /// \see \a clearAndDispose() if the nodes should be deleted.
230 void clear() { Sentinel.reset(); }
231
232 /// Clear the list and dispose of the nodes.
233 template <class Disposer> void clearAndDispose(Disposer dispose) {
234 eraseAndDispose(begin(), end(), dispose);
235 }
236
237 /// Splice in another list.
238 void splice(iterator I, simple_ilist &L2) {
239 splice(I, L2, L2.begin(), L2.end());
240 }
241
242 /// Splice in a node from another list.
243 void splice(iterator I, simple_ilist &L2, iterator Node) {
244 splice(I, L2, Node, std::next(Node));
245 }
246
247 /// Splice in a range of nodes from another list.
248 void splice(iterator I, simple_ilist &, iterator First, iterator Last) {
249 list_base_type::transferBefore(*I.getNodePtr(), *First.getNodePtr(),
250 *Last.getNodePtr());
251 }
252
253 /// Merge in another list.
254 ///
255 /// \pre \c this and \p RHS are sorted.
256 ///@{
257 void merge(simple_ilist &RHS) { merge(RHS, std::less<T>()); }
258 template <class Compare> void merge(simple_ilist &RHS, Compare comp);
259 ///@}
260
261 /// Sort the list.
262 ///@{
263 void sort() { sort(std::less<T>()); }
264 template <class Compare> void sort(Compare comp);
265 ///@}
266};
267
268template <class T, class... Options>
269template <class Compare>
270void simple_ilist<T, Options...>::merge(simple_ilist &RHS, Compare comp) {
271 if (this == &RHS || RHS.empty())
272 return;
273 iterator LI = begin(), LE = end();
274 iterator RI = RHS.begin(), RE = RHS.end();
275 while (LI != LE) {
276 if (comp(*RI, *LI)) {
277 // Transfer a run of at least size 1 from RHS to LHS.
278 iterator RunStart = RI++;
279 RI = std::find_if(RI, RE, [&](reference RV) { return !comp(RV, *LI); });
280 splice(LI, RHS, RunStart, RI);
281 if (RI == RE)
282 return;
283 }
284 ++LI;
285 }
286 // Transfer the remaining RHS nodes once LHS is finished.
287 splice(LE, RHS, RI, RE);
288}
289
290template <class T, class... Options>
291template <class Compare>
292void simple_ilist<T, Options...>::sort(Compare comp) {
293 // Vacuously sorted.
294 if (empty() || std::next(begin()) == end())
295 return;
296
297 // Split the list in the middle.
298 iterator Center = begin(), End = begin();
299 while (End != end() && ++End != end()) {
300 ++Center;
301 ++End;
302 }
303 simple_ilist RHS;
304 RHS.splice(RHS.end(), *this, Center, end());
305
306 // Sort the sublists and merge back together.
307 sort(comp);
308 RHS.sort(comp);
309 merge(RHS, comp);
310}
311
312} // end namespace llvm
313
314#endif // LLVM_ADT_SIMPLE_ILIST_H
315