1//===- llvm/ADT/simple_ilist.h - Simple Intrusive List ----------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef LLVM_ADT_SIMPLE_ILIST_H
11#define LLVM_ADT_SIMPLE_ILIST_H
12
13#include "llvm/ADT/ilist_base.h"
14#include "llvm/ADT/ilist_iterator.h"
15#include "llvm/ADT/ilist_node.h"
16#include <algorithm>
17#include <cassert>
18#include <cstddef>
19
20namespace llvm {
21
22/// A simple intrusive list implementation.
23///
24/// This is a simple intrusive list for a \c T that inherits from \c
25/// ilist_node<T>.  The list never takes ownership of anything inserted in it.
26///
27/// Unlike \a iplist<T> and \a ilist<T>, \a simple_ilist<T> never allocates or
28/// deletes values, and has no callback traits.
29///
30/// The API for adding nodes include \a push_front(), \a push_back(), and \a
31/// insert().  These all take values by reference (not by pointer), except for
32/// the range version of \a insert().
33///
34/// There are three sets of API for discarding nodes from the list: \a
35/// remove(), which takes a reference to the node to remove, \a erase(), which
36/// takes an iterator or iterator range and returns the next one, and \a
37/// clear(), which empties out the container.  All three are constant time
38/// operations.  None of these deletes any nodes; in particular, if there is a
39/// single node in the list, then these have identical semantics:
40/// \li \c L.remove(L.front());
41/// \li \c L.erase(L.begin());
42/// \li \c L.clear();
43///
44/// As a convenience for callers, there are parallel APIs that take a \c
45/// Disposer (such as \c std::default_delete<T>): \a removeAndDispose(), \a
46/// eraseAndDispose(), and \a clearAndDispose().  These have different names
47/// because the extra semantic is otherwise non-obvious.  They are equivalent
48/// to calling \a std::for_each() on the range to be discarded.
49///
50/// The currently available \p Options customize the nodes in the list.  The
51/// same options must be specified in the \a ilist_node instantation for
52/// compatibility (although the order is irrelevant).
53/// \li Use \a ilist_tag to designate which ilist_node for a given \p T this
54/// list should use.  This is useful if a type \p T is part of multiple,
55/// independent lists simultaneously.
56/// \li Use \a ilist_sentinel_tracking to always (or never) track whether a
57/// node is a sentinel.  Specifying \c true enables the \a
58/// ilist_node::isSentinel() API.  Unlike \a ilist_node::isKnownSentinel(),
59/// which is only appropriate for assertions, \a ilist_node::isSentinel() is
60/// appropriate for real logic.
61///
62/// Here are examples of \p Options usage:
63/// \li \c simple_ilist<T> gives the defaults.  \li \c
64/// simple_ilist<T,ilist_sentinel_tracking<true>> enables the \a
65/// ilist_node::isSentinel() API.
66/// \li \c simple_ilist<T,ilist_tag<A>,ilist_sentinel_tracking<false>>
67/// specifies a tag of A and that tracking should be off (even when
68/// LLVM_ENABLE_ABI_BREAKING_CHECKS are enabled).
69/// \li \c simple_ilist<T,ilist_sentinel_tracking<false>,ilist_tag<A>> is
70/// equivalent to the last.
71///
72/// See \a is_valid_option for steps on adding a new option.
73template <typename T, class... Options>
74class simple_ilist
75    : ilist_detail::compute_node_options<T, Options...>::type::list_base_type,
76      ilist_detail::SpecificNodeAccess<
77          typename ilist_detail::compute_node_options<T, Options...>::type> {
78  static_assert(ilist_detail::check_options<Options...>::value,
79                "Unrecognized node option!");
80  typedef
81      typename ilist_detail::compute_node_options<T, Options...>::type OptionsT;
82  typedef typename OptionsT::list_base_type list_base_type;
83  ilist_sentinel<OptionsT> Sentinel;
84
85public:
86  typedef typename OptionsT::value_type value_type;
87  typedef typename OptionsT::pointer pointer;
88  typedef typename OptionsT::reference reference;
89  typedef typename OptionsT::const_pointer const_pointer;
90  typedef typename OptionsT::const_reference const_reference;
91  typedef ilist_iterator<OptionsT, false, false> iterator;
92  typedef ilist_iterator<OptionsT, false, true> const_iterator;
93  typedef ilist_iterator<OptionsT, true, false> reverse_iterator;
94  typedef ilist_iterator<OptionsT, true, true> const_reverse_iterator;
95  typedef size_t size_type;
96  typedef ptrdiff_t difference_type;
97
98  simple_ilist() = default;
99  ~simple_ilist() = default;
100
101  // No copy constructors.
102  simple_ilist(const simple_ilist &) = delete;
103  simple_ilist &operator=(const simple_ilist &) = delete;
104
105  // Move constructors.
106  simple_ilist(simple_ilist &&X) { splice(end(), X); }
107  simple_ilist &operator=(simple_ilist &&X) {
108    clear();
109    splice(end(), X);
110    return *this;
111  }
112
113  iterator begin() { return ++iterator(Sentinel); }
114  const_iterator begin() const { return ++const_iterator(Sentinel); }
115  iterator end() { return iterator(Sentinel); }
116  const_iterator end() const { return const_iterator(Sentinel); }
117  reverse_iterator rbegin() { return ++reverse_iterator(Sentinel); }
118  const_reverse_iterator rbegin() const {
119    return ++const_reverse_iterator(Sentinel);
120  }
121  reverse_iterator rend() { return reverse_iterator(Sentinel); }
122  const_reverse_iterator rend() const {
123    return const_reverse_iterator(Sentinel);
124  }
125
126  /// Check if the list is empty in constant time.
127  LLVM_NODISCARD bool empty() const { return Sentinel.empty(); }
128
129  /// Calculate the size of the list in linear time.
130  LLVM_NODISCARD size_type size() const {
131    return std::distance(begin(), end());
132  }
133
134  reference front() { return *begin(); }
135  const_reference front() const { return *begin(); }
136  reference back() { return *rbegin(); }
137  const_reference back() const { return *rbegin(); }
138
139  /// Insert a node at the front; never copies.
140  void push_front(reference Node) { insert(begin(), Node); }
141
142  /// Insert a node at the back; never copies.
143  void push_back(reference Node) { insert(end(), Node); }
144
145  /// Remove the node at the front; never deletes.
146  void pop_front() { erase(begin()); }
147
148  /// Remove the node at the back; never deletes.
149  void pop_back() { erase(--end()); }
150
151  /// Swap with another list in place using std::swap.
152  void swap(simple_ilist &X) { std::swap(*this, X); }
153
154  /// Insert a node by reference; never copies.
155  iterator insert(iterator I, reference Node) {
156    list_base_type::insertBefore(*I.getNodePtr(), *this->getNodePtr(&Node));
157    return iterator(&Node);
158  }
159
160  /// Insert a range of nodes; never copies.
161  template <class Iterator>
162  void insert(iterator I, Iterator First, Iterator Last) {
163    for (; First != Last; ++First)
164      insert(I, *First);
165  }
166
167  /// Clone another list.
168  template <class Cloner, class Disposer>
169  void cloneFrom(const simple_ilist &L2, Cloner clone, Disposer dispose) {
170    clearAndDispose(dispose);
171    for (const_reference V : L2)
172      push_back(*clone(V));
173  }
174
175  /// Remove a node by reference; never deletes.
176  ///
177  /// \see \a erase() for removing by iterator.
178  /// \see \a removeAndDispose() if the node should be deleted.
179  void remove(reference N) { list_base_type::remove(*this->getNodePtr(&N)); }
180
181  /// Remove a node by reference and dispose of it.
182  template <class Disposer>
183  void removeAndDispose(reference N, Disposer dispose) {
184    remove(N);
185    dispose(&N);
186  }
187
188  /// Remove a node by iterator; never deletes.
189  ///
190  /// \see \a remove() for removing by reference.
191  /// \see \a eraseAndDispose() it the node should be deleted.
192  iterator erase(iterator I) {
193    assert(I != end() && "Cannot remove end of list!");
194    remove(*I++);
195    return I;
196  }
197
198  /// Remove a range of nodes; never deletes.
199  ///
200  /// \see \a eraseAndDispose() if the nodes should be deleted.
201  iterator erase(iterator First, iterator Last) {
202    list_base_type::removeRange(*First.getNodePtr(), *Last.getNodePtr());
203    return Last;
204  }
205
206  /// Remove a node by iterator and dispose of it.
207  template <class Disposer>
208  iterator eraseAndDispose(iterator I, Disposer dispose) {
209    auto Next = std::next(I);
210    erase(I);
211    dispose(&*I);
212    return Next;
213  }
214
215  /// Remove a range of nodes and dispose of them.
216  template <class Disposer>
217  iterator eraseAndDispose(iterator First, iterator Last, Disposer dispose) {
218    while (First != Last)
219      First = eraseAndDispose(First, dispose);
220    return Last;
221  }
222
223  /// Clear the list; never deletes.
224  ///
225  /// \see \a clearAndDispose() if the nodes should be deleted.
226  void clear() { Sentinel.reset(); }
227
228  /// Clear the list and dispose of the nodes.
229  template <class Disposer> void clearAndDispose(Disposer dispose) {
230    eraseAndDispose(begin(), end(), dispose);
231  }
232
233  /// Splice in another list.
234  void splice(iterator I, simple_ilist &L2) {
235    splice(I, L2, L2.begin(), L2.end());
236  }
237
238  /// Splice in a node from another list.
239  void splice(iterator I, simple_ilist &L2, iterator Node) {
240    splice(I, L2, Node, std::next(Node));
241  }
242
243  /// Splice in a range of nodes from another list.
244  void splice(iterator I, simple_ilist &, iterator First, iterator Last) {
245    list_base_type::transferBefore(*I.getNodePtr(), *First.getNodePtr(),
246                                   *Last.getNodePtr());
247  }
248
249  /// Merge in another list.
250  ///
251  /// \pre \c this and \p RHS are sorted.
252  ///@{
253  void merge(simple_ilist &RHS) { merge(RHS, std::less<T>()); }
254  template <class Compare> void merge(simple_ilist &RHS, Compare comp);
255  ///@}
256
257  /// Sort the list.
258  ///@{
259  void sort() { sort(std::less<T>()); }
260  template <class Compare> void sort(Compare comp);
261  ///@}
262};
263
264template <class T, class... Options>
265template <class Compare>
266void simple_ilist<T, Options...>::merge(simple_ilist &RHS, Compare comp) {
267  if (this == &RHS || RHS.empty())
268    return;
269  iterator LI = begin(), LE = end();
270  iterator RI = RHS.begin(), RE = RHS.end();
271  while (LI != LE) {
272    if (comp(*RI, *LI)) {
273      // Transfer a run of at least size 1 from RHS to LHS.
274      iterator RunStart = RI++;
275      RI = std::find_if(RI, RE, [&](reference RV) { return !comp(RV, *LI); });
276      splice(LI, RHS, RunStart, RI);
277      if (RI == RE)
278        return;
279    }
280    ++LI;
281  }
282  // Transfer the remaining RHS nodes once LHS is finished.
283  splice(LE, RHS, RI, RE);
284}
285
286template <class T, class... Options>
287template <class Compare>
288void simple_ilist<T, Options...>::sort(Compare comp) {
289  // Vacuously sorted.
290  if (empty() || std::next(begin()) == end())
291    return;
292
293  // Split the list in the middle.
294  iterator Center = begin(), End = begin();
295  while (End != end() && ++End != end()) {
296    ++Center;
297    ++End;
298  }
299  simple_ilist RHS;
300  RHS.splice(RHS.end(), *this, Center, end());
301
302  // Sort the sublists and merge back together.
303  sort(comp);
304  RHS.sort(comp);
305  merge(RHS, comp);
306}
307
308} // end namespace llvm
309
310#endif // LLVM_ADT_SIMPLE_ILIST_H
311