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  [[nodiscard]] bool empty() const { return Sentinel.empty(); }
132
133  /// Calculate the size of the list in linear time.
134  [[nodiscard]] size_type size() const { return std::distance(begin(), end()); }
135
136  reference front() { return *begin(); }
137  const_reference front() const { return *begin(); }
138  reference back() { return *rbegin(); }
139  const_reference back() const { return *rbegin(); }
140
141  /// Insert a node at the front; never copies.
142  void push_front(reference Node) { insert(begin(), Node); }
143
144  /// Insert a node at the back; never copies.
145  void push_back(reference Node) { insert(end(), Node); }
146
147  /// Remove the node at the front; never deletes.
148  void pop_front() { erase(begin()); }
149
150  /// Remove the node at the back; never deletes.
151  void pop_back() { erase(--end()); }
152
153  /// Swap with another list in place using std::swap.
154  void swap(simple_ilist &X) { std::swap(*this, X); }
155
156  /// Insert a node by reference; never copies.
157  iterator insert(iterator I, reference Node) {
158    list_base_type::insertBefore(*I.getNodePtr(), *this->getNodePtr(&Node));
159    return iterator(&Node);
160  }
161
162  /// Insert a range of nodes; never copies.
163  template <class Iterator>
164  void insert(iterator I, Iterator First, Iterator Last) {
165    for (; First != Last; ++First)
166      insert(I, *First);
167  }
168
169  /// Clone another list.
170  template <class Cloner, class Disposer>
171  void cloneFrom(const simple_ilist &L2, Cloner clone, Disposer dispose) {
172    clearAndDispose(dispose);
173    for (const_reference V : L2)
174      push_back(*clone(V));
175  }
176
177  /// Remove a node by reference; never deletes.
178  ///
179  /// \see \a erase() for removing by iterator.
180  /// \see \a removeAndDispose() if the node should be deleted.
181  void remove(reference N) { list_base_type::remove(*this->getNodePtr(&N)); }
182
183  /// Remove a node by reference and dispose of it.
184  template <class Disposer>
185  void removeAndDispose(reference N, Disposer dispose) {
186    remove(N);
187    dispose(&N);
188  }
189
190  /// Remove a node by iterator; never deletes.
191  ///
192  /// \see \a remove() for removing by reference.
193  /// \see \a eraseAndDispose() it the node should be deleted.
194  iterator erase(iterator I) {
195    assert(I != end() && "Cannot remove end of list!");
196    remove(*I++);
197    return I;
198  }
199
200  /// Remove a range of nodes; never deletes.
201  ///
202  /// \see \a eraseAndDispose() if the nodes should be deleted.
203  iterator erase(iterator First, iterator Last) {
204    list_base_type::removeRange(*First.getNodePtr(), *Last.getNodePtr());
205    return Last;
206  }
207
208  /// Remove a node by iterator and dispose of it.
209  template <class Disposer>
210  iterator eraseAndDispose(iterator I, Disposer dispose) {
211    auto Next = std::next(I);
212    erase(I);
213    dispose(&*I);
214    return Next;
215  }
216
217  /// Remove a range of nodes and dispose of them.
218  template <class Disposer>
219  iterator eraseAndDispose(iterator First, iterator Last, Disposer dispose) {
220    while (First != Last)
221      First = eraseAndDispose(First, dispose);
222    return Last;
223  }
224
225  /// Clear the list; never deletes.
226  ///
227  /// \see \a clearAndDispose() if the nodes should be deleted.
228  void clear() { Sentinel.reset(); }
229
230  /// Clear the list and dispose of the nodes.
231  template <class Disposer> void clearAndDispose(Disposer dispose) {
232    eraseAndDispose(begin(), end(), dispose);
233  }
234
235  /// Splice in another list.
236  void splice(iterator I, simple_ilist &L2) {
237    splice(I, L2, L2.begin(), L2.end());
238  }
239
240  /// Splice in a node from another list.
241  void splice(iterator I, simple_ilist &L2, iterator Node) {
242    splice(I, L2, Node, std::next(Node));
243  }
244
245  /// Splice in a range of nodes from another list.
246  void splice(iterator I, simple_ilist &, iterator First, iterator Last) {
247    list_base_type::transferBefore(*I.getNodePtr(), *First.getNodePtr(),
248                                   *Last.getNodePtr());
249  }
250
251  /// Merge in another list.
252  ///
253  /// \pre \c this and \p RHS are sorted.
254  ///@{
255  void merge(simple_ilist &RHS) { merge(RHS, std::less<T>()); }
256  template <class Compare> void merge(simple_ilist &RHS, Compare comp);
257  ///@}
258
259  /// Sort the list.
260  ///@{
261  void sort() { sort(std::less<T>()); }
262  template <class Compare> void sort(Compare comp);
263  ///@}
264};
265
266template <class T, class... Options>
267template <class Compare>
268void simple_ilist<T, Options...>::merge(simple_ilist &RHS, Compare comp) {
269  if (this == &RHS || RHS.empty())
270    return;
271  iterator LI = begin(), LE = end();
272  iterator RI = RHS.begin(), RE = RHS.end();
273  while (LI != LE) {
274    if (comp(*RI, *LI)) {
275      // Transfer a run of at least size 1 from RHS to LHS.
276      iterator RunStart = RI++;
277      RI = std::find_if(RI, RE, [&](reference RV) { return !comp(RV, *LI); });
278      splice(LI, RHS, RunStart, RI);
279      if (RI == RE)
280        return;
281    }
282    ++LI;
283  }
284  // Transfer the remaining RHS nodes once LHS is finished.
285  splice(LE, RHS, RI, RE);
286}
287
288template <class T, class... Options>
289template <class Compare>
290void simple_ilist<T, Options...>::sort(Compare comp) {
291  // Vacuously sorted.
292  if (empty() || std::next(begin()) == end())
293    return;
294
295  // Split the list in the middle.
296  iterator Center = begin(), End = begin();
297  while (End != end() && ++End != end()) {
298    ++Center;
299    ++End;
300  }
301  simple_ilist RHS;
302  RHS.splice(RHS.end(), *this, Center, end());
303
304  // Sort the sublists and merge back together.
305  sort(comp);
306  RHS.sort(comp);
307  merge(RHS, comp);
308}
309
310} // end namespace llvm
311
312#endif // LLVM_ADT_SIMPLE_ILIST_H
313