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//===- llvm/ADT/simple_ilist.h - Simple Intrusive List ----------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/ilist_base.h"
#include "llvm/ADT/ilist_iterator.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/ADT/ilist_node_options.h"
#include "llvm/Support/Compiler.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <functional>
#include <iterator>
#include <utility>
namespace llvm {
/// A simple intrusive list implementation.
/// This is a simple intrusive list for a \c T that inherits from \c
/// ilist_node<T>. The list never takes ownership of anything inserted in it.
/// Unlike \a iplist<T> and \a ilist<T>, \a simple_ilist<T> never allocates or
/// deletes values, and has no callback traits.
/// The API for adding nodes include \a push_front(), \a push_back(), and \a
/// insert(). These all take values by reference (not by pointer), except for
/// the range version of \a insert().
/// There are three sets of API for discarding nodes from the list: \a
/// remove(), which takes a reference to the node to remove, \a erase(), which
/// takes an iterator or iterator range and returns the next one, and \a
/// clear(), which empties out the container. All three are constant time
/// operations. None of these deletes any nodes; in particular, if there is a
/// single node in the list, then these have identical semantics:
/// \li \c L.remove(L.front());
/// \li \c L.erase(L.begin());
/// \li \c L.clear();
/// As a convenience for callers, there are parallel APIs that take a \c
/// Disposer (such as \c std::default_delete<T>): \a removeAndDispose(), \a
/// eraseAndDispose(), and \a clearAndDispose(). These have different names
/// because the extra semantic is otherwise non-obvious. They are equivalent
/// to calling \a std::for_each() on the range to be discarded.
/// The currently available \p Options customize the nodes in the list. The
/// same options must be specified in the \a ilist_node instantation for
/// compatibility (although the order is irrelevant).
/// \li Use \a ilist_tag to designate which ilist_node for a given \p T this
/// list should use. This is useful if a type \p T is part of multiple,
/// independent lists simultaneously.
/// \li Use \a ilist_sentinel_tracking to always (or never) track whether a
/// node is a sentinel. Specifying \c true enables the \a
/// ilist_node::isSentinel() API. Unlike \a ilist_node::isKnownSentinel(),
/// which is only appropriate for assertions, \a ilist_node::isSentinel() is
/// appropriate for real logic.
/// Here are examples of \p Options usage:
/// \li \c simple_ilist<T> gives the defaults. \li \c
/// simple_ilist<T,ilist_sentinel_tracking<true>> enables the \a
/// ilist_node::isSentinel() API.
/// \li \c simple_ilist<T,ilist_tag<A>,ilist_sentinel_tracking<false>>
/// specifies a tag of A and that tracking should be off (even when
/// \li \c simple_ilist<T,ilist_sentinel_tracking<false>,ilist_tag<A>> is
/// equivalent to the last.
/// See \a is_valid_option for steps on adding a new option.
template <typename T, class... Options>
class simple_ilist
: ilist_detail::compute_node_options<T, Options...>::type::list_base_type,
typename ilist_detail::compute_node_options<T, Options...>::type> {
"Unrecognized node option!");
using OptionsT =
typename ilist_detail::compute_node_options<T, Options...>::type;
using list_base_type = typename OptionsT::list_base_type;
ilist_sentinel<OptionsT> Sentinel;
using value_type = typename OptionsT::value_type;
using pointer = typename OptionsT::pointer;
using reference = typename OptionsT::reference;
using const_pointer = typename OptionsT::const_pointer;
using const_reference = typename OptionsT::const_reference;
using iterator = ilist_iterator<OptionsT, false, false>;
using const_iterator = ilist_iterator<OptionsT, false, true>;
using reverse_iterator = ilist_iterator<OptionsT, true, false>;
using const_reverse_iterator = ilist_iterator<OptionsT, true, true>;
using size_type = size_t;
using difference_type = ptrdiff_t;
simple_ilist() = default;
~simple_ilist() = default;
// No copy constructors.
simple_ilist(const simple_ilist &) = delete;
simple_ilist &operator=(const simple_ilist &) = delete;
// Move constructors.
simple_ilist(simple_ilist &&X) { splice(end(), X); }
simple_ilist &operator=(simple_ilist &&X) {
splice(end(), X);
return *this;
iterator begin() { return ++iterator(Sentinel); }
const_iterator begin() const { return ++const_iterator(Sentinel); }
iterator end() { return iterator(Sentinel); }
const_iterator end() const { return const_iterator(Sentinel); }
reverse_iterator rbegin() { return ++reverse_iterator(Sentinel); }
const_reverse_iterator rbegin() const {
return ++const_reverse_iterator(Sentinel);
reverse_iterator rend() { return reverse_iterator(Sentinel); }
const_reverse_iterator rend() const {
return const_reverse_iterator(Sentinel);
/// Check if the list is empty in constant time.
LLVM_NODISCARD bool empty() const { return Sentinel.empty(); }
/// Calculate the size of the list in linear time.
LLVM_NODISCARD size_type size() const {
return std::distance(begin(), end());
reference front() { return *begin(); }
const_reference front() const { return *begin(); }
reference back() { return *rbegin(); }
const_reference back() const { return *rbegin(); }
/// Insert a node at the front; never copies.
void push_front(reference Node) { insert(begin(), Node); }
/// Insert a node at the back; never copies.
void push_back(reference Node) { insert(end(), Node); }
/// Remove the node at the front; never deletes.
void pop_front() { erase(begin()); }
/// Remove the node at the back; never deletes.
void pop_back() { erase(--end()); }
/// Swap with another list in place using std::swap.
void swap(simple_ilist &X) { std::swap(*this, X); }
/// Insert a node by reference; never copies.
iterator insert(iterator I, reference Node) {
list_base_type::insertBefore(*I.getNodePtr(), *this->getNodePtr(&Node));
return iterator(&Node);
/// Insert a range of nodes; never copies.
template <class Iterator>
void insert(iterator I, Iterator First, Iterator Last) {
for (; First != Last; ++First)
insert(I, *First);
/// Clone another list.
template <class Cloner, class Disposer>
void cloneFrom(const simple_ilist &L2, Cloner clone, Disposer dispose) {
for (const_reference V : L2)
/// Remove a node by reference; never deletes.
/// \see \a erase() for removing by iterator.
/// \see \a removeAndDispose() if the node should be deleted.
void remove(reference N) { list_base_type::remove(*this->getNodePtr(&N)); }
/// Remove a node by reference and dispose of it.
template <class Disposer>
void removeAndDispose(reference N, Disposer dispose) {
/// Remove a node by iterator; never deletes.
/// \see \a remove() for removing by reference.
/// \see \a eraseAndDispose() it the node should be deleted.
iterator erase(iterator I) {
assert(I != end() && "Cannot remove end of list!");
return I;
/// Remove a range of nodes; never deletes.
/// \see \a eraseAndDispose() if the nodes should be deleted.
iterator erase(iterator First, iterator Last) {
list_base_type::removeRange(*First.getNodePtr(), *Last.getNodePtr());
return Last;
/// Remove a node by iterator and dispose of it.
template <class Disposer>
iterator eraseAndDispose(iterator I, Disposer dispose) {
auto Next = std::next(I);
return Next;
/// Remove a range of nodes and dispose of them.
template <class Disposer>
iterator eraseAndDispose(iterator First, iterator Last, Disposer dispose) {
while (First != Last)
First = eraseAndDispose(First, dispose);
return Last;
/// Clear the list; never deletes.
/// \see \a clearAndDispose() if the nodes should be deleted.
void clear() { Sentinel.reset(); }
/// Clear the list and dispose of the nodes.
template <class Disposer> void clearAndDispose(Disposer dispose) {
eraseAndDispose(begin(), end(), dispose);
/// Splice in another list.
void splice(iterator I, simple_ilist &L2) {
splice(I, L2, L2.begin(), L2.end());
/// Splice in a node from another list.
void splice(iterator I, simple_ilist &L2, iterator Node) {
splice(I, L2, Node, std::next(Node));
/// Splice in a range of nodes from another list.
void splice(iterator I, simple_ilist &, iterator First, iterator Last) {
list_base_type::transferBefore(*I.getNodePtr(), *First.getNodePtr(),
/// Merge in another list.
/// \pre \c this and \p RHS are sorted.
void merge(simple_ilist &RHS) { merge(RHS, std::less<T>()); }
template <class Compare> void merge(simple_ilist &RHS, Compare comp);
/// Sort the list.
void sort() { sort(std::less<T>()); }
template <class Compare> void sort(Compare comp);
template <class T, class... Options>
template <class Compare>
void simple_ilist<T, Options...>::merge(simple_ilist &RHS, Compare comp) {
if (this == &RHS || RHS.empty())
iterator LI = begin(), LE = end();
iterator RI = RHS.begin(), RE = RHS.end();
while (LI != LE) {
if (comp(*RI, *LI)) {
// Transfer a run of at least size 1 from RHS to LHS.
iterator RunStart = RI++;
RI = std::find_if(RI, RE, [&](reference RV) { return !comp(RV, *LI); });
splice(LI, RHS, RunStart, RI);
if (RI == RE)
// Transfer the remaining RHS nodes once LHS is finished.
splice(LE, RHS, RI, RE);
template <class T, class... Options>
template <class Compare>
void simple_ilist<T, Options...>::sort(Compare comp) {
// Vacuously sorted.
if (empty() || std::next(begin()) == end())
// Split the list in the middle.
iterator Center = begin(), End = begin();
while (End != end() && ++End != end()) {
simple_ilist RHS;
RHS.splice(RHS.end(), *this, Center, end());
// Sort the sublists and merge back together.
merge(RHS, comp);
} // end namespace llvm