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 =
96 typename ilist_select_iterator_type<OptionsT::has_iterator_bits, OptionsT,
97 false, false>::type;
98 using const_iterator =
99 typename ilist_select_iterator_type<OptionsT::has_iterator_bits, OptionsT,
100 false, true>::type;
101 using reverse_iterator =
102 typename ilist_select_iterator_type<OptionsT::has_iterator_bits, OptionsT,
103 true, false>::type;
104 using const_reverse_iterator =
105 typename ilist_select_iterator_type<OptionsT::has_iterator_bits, OptionsT,
106 true, true>::type;
107 using size_type = size_t;
108 using difference_type = ptrdiff_t;
109
110 simple_ilist() = default;
111 ~simple_ilist() = default;
112
113 // No copy constructors.
114 simple_ilist(const simple_ilist &) = delete;
115 simple_ilist &operator=(const simple_ilist &) = delete;
116
117 // Move constructors.
118 simple_ilist(simple_ilist &&X) { splice(end(), X); }
119 simple_ilist &operator=(simple_ilist &&X) {
120 clear();
121 splice(end(), X);
122 return *this;
123 }
124
125 iterator begin() { return ++iterator(Sentinel); }
126 const_iterator begin() const { return ++const_iterator(Sentinel); }
127 iterator end() { return iterator(Sentinel); }
128 const_iterator end() const { return const_iterator(Sentinel); }
129 reverse_iterator rbegin() { return ++reverse_iterator(Sentinel); }
130 const_reverse_iterator rbegin() const {
131 return ++const_reverse_iterator(Sentinel);
132 }
133 reverse_iterator rend() { return reverse_iterator(Sentinel); }
134 const_reverse_iterator rend() const {
135 return const_reverse_iterator(Sentinel);
136 }
137
138 /// Check if the list is empty in constant time.
139 [[nodiscard]] bool empty() const { return Sentinel.empty(); }
140
141 /// Calculate the size of the list in linear time.
142 [[nodiscard]] size_type size() const { return std::distance(begin(), end()); }
143
144 reference front() { return *begin(); }
145 const_reference front() const { return *begin(); }
146 reference back() { return *rbegin(); }
147 const_reference back() const { return *rbegin(); }
148
149 /// Insert a node at the front; never copies.
150 void push_front(reference Node) { insert(begin(), Node); }
151
152 /// Insert a node at the back; never copies.
153 void push_back(reference Node) { insert(end(), Node); }
154
155 /// Remove the node at the front; never deletes.
156 void pop_front() { erase(begin()); }
157
158 /// Remove the node at the back; never deletes.
159 void pop_back() { erase(--end()); }
160
161 /// Swap with another list in place using std::swap.
162 void swap(simple_ilist &X) { std::swap(*this, X); }
163
164 /// Insert a node by reference; never copies.
165 iterator insert(iterator I, reference Node) {
166 list_base_type::insertBefore(*I.getNodePtr(), *this->getNodePtr(&Node));
167 return iterator(&Node);
168 }
169
170 /// Insert a range of nodes; never copies.
171 template <class Iterator>
172 void insert(iterator I, Iterator First, Iterator Last) {
173 for (; First != Last; ++First)
174 insert(I, *First);
175 }
176
177 /// Clone another list.
178 template <class Cloner, class Disposer>
179 void cloneFrom(const simple_ilist &L2, Cloner clone, Disposer dispose) {
180 clearAndDispose(dispose);
181 for (const_reference V : L2)
182 push_back(Node: *clone(V));
183 }
184
185 /// Remove a node by reference; never deletes.
186 ///
187 /// \see \a erase() for removing by iterator.
188 /// \see \a removeAndDispose() if the node should be deleted.
189 void remove(reference N) { list_base_type::remove(*this->getNodePtr(&N)); }
190
191 /// Remove a node by reference and dispose of it.
192 template <class Disposer>
193 void removeAndDispose(reference N, Disposer dispose) {
194 remove(N);
195 dispose(&N);
196 }
197
198 /// Remove a node by iterator; never deletes.
199 ///
200 /// \see \a remove() for removing by reference.
201 /// \see \a eraseAndDispose() it the node should be deleted.
202 iterator erase(iterator I) {
203 assert(I != end() && "Cannot remove end of list!");
204 remove(N: *I++);
205 return I;
206 }
207
208 /// Remove a range of nodes; never deletes.
209 ///
210 /// \see \a eraseAndDispose() if the nodes should be deleted.
211 iterator erase(iterator First, iterator Last) {
212 list_base_type::removeRange(*First.getNodePtr(), *Last.getNodePtr());
213 return Last;
214 }
215
216 /// Remove a node by iterator and dispose of it.
217 template <class Disposer>
218 iterator eraseAndDispose(iterator I, Disposer dispose) {
219 auto Next = std::next(I);
220 erase(I);
221 dispose(&*I);
222 return Next;
223 }
224
225 /// Remove a range of nodes and dispose of them.
226 template <class Disposer>
227 iterator eraseAndDispose(iterator First, iterator Last, Disposer dispose) {
228 while (First != Last)
229 First = eraseAndDispose(First, dispose);
230 return Last;
231 }
232
233 /// Clear the list; never deletes.
234 ///
235 /// \see \a clearAndDispose() if the nodes should be deleted.
236 void clear() { Sentinel.reset(); }
237
238 /// Clear the list and dispose of the nodes.
239 template <class Disposer> void clearAndDispose(Disposer dispose) {
240 eraseAndDispose(begin(), end(), dispose);
241 }
242
243 /// Splice in another list.
244 void splice(iterator I, simple_ilist &L2) {
245 splice(I, L2, L2.begin(), L2.end());
246 }
247
248 /// Splice in a node from another list.
249 void splice(iterator I, simple_ilist &L2, iterator Node) {
250 splice(I, L2, Node, std::next(Node));
251 }
252
253 /// Splice in a range of nodes from another list.
254 void splice(iterator I, simple_ilist &, iterator First, iterator Last) {
255 list_base_type::transferBefore(*I.getNodePtr(), *First.getNodePtr(),
256 *Last.getNodePtr());
257 }
258
259 /// Merge in another list.
260 ///
261 /// \pre \c this and \p RHS are sorted.
262 ///@{
263 void merge(simple_ilist &RHS) { merge(RHS, std::less<T>()); }
264 template <class Compare> void merge(simple_ilist &RHS, Compare comp);
265 ///@}
266
267 /// Sort the list.
268 ///@{
269 void sort() { sort(std::less<T>()); }
270 template <class Compare> void sort(Compare comp);
271 ///@}
272};
273
274template <class T, class... Options>
275template <class Compare>
276void simple_ilist<T, Options...>::merge(simple_ilist &RHS, Compare comp) {
277 if (this == &RHS || RHS.empty())
278 return;
279 iterator LI = begin(), LE = end();
280 iterator RI = RHS.begin(), RE = RHS.end();
281 while (LI != LE) {
282 if (comp(*RI, *LI)) {
283 // Transfer a run of at least size 1 from RHS to LHS.
284 iterator RunStart = RI++;
285 RI = std::find_if(RI, RE, [&](reference RV) { return !comp(RV, *LI); });
286 splice(LI, RHS, RunStart, RI);
287 if (RI == RE)
288 return;
289 }
290 ++LI;
291 }
292 // Transfer the remaining RHS nodes once LHS is finished.
293 splice(LE, RHS, RI, RE);
294}
295
296template <class T, class... Options>
297template <class Compare>
298void simple_ilist<T, Options...>::sort(Compare comp) {
299 // Vacuously sorted.
300 if (empty() || std::next(begin()) == end())
301 return;
302
303 // Split the list in the middle.
304 iterator Center = begin(), End = begin();
305 while (End != end() && ++End != end()) {
306 ++Center;
307 ++End;
308 }
309 simple_ilist RHS;
310 RHS.splice(RHS.end(), *this, Center, end());
311
312 // Sort the sublists and merge back together.
313 sort(comp);
314 RHS.sort(comp);
315 merge(RHS, comp);
316}
317
318} // end namespace llvm
319
320#endif // LLVM_ADT_SIMPLE_ILIST_H
321

source code of llvm/include/llvm/ADT/simple_ilist.h