llvm/llvm/include/llvm/ADT/ilist_node.h

//===- llvm/ADT/ilist_node.h - Intrusive Linked List Helper -----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines the ilist_node class template, which is a convenient
/// base class for creating classes that can be used with ilists.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_ILIST_NODE_H
#define LLVM_ADT_ILIST_NODE_H

#include "llvm/ADT/ilist_node_base.h"
#include "llvm/ADT/ilist_node_options.h"

namespace llvm {

namespace ilist_detail {

struct NodeAccess;

/// Mixin base class that is used to add \a getParent() and
/// \a setParent(ParentTy*) methods to \a ilist_node_impl iff \a ilist_parent
/// has been set in the list options.
template <class NodeTy, class ParentTy> class node_parent_access { … };
node_parent_access<NodeTy, void>;

} // end namespace ilist_detail

template <class OptionsT, bool IsReverse, bool IsConst> class ilist_iterator;
template <class OptionsT, bool IsReverse, bool IsConst>
class ilist_iterator_w_bits;
template <class OptionsT> class ilist_sentinel;

// Selector for which iterator type to pick given the iterator-bits node option.
template <bool use_iterator_bits, typename Opts, bool arg1, bool arg2>
class ilist_select_iterator_type { … };
ilist_select_iterator_type<true, Opts, arg1, arg2>;

/// Implementation for an ilist node.
///
/// Templated on an appropriate \a ilist_detail::node_options, usually computed
/// by \a ilist_detail::compute_node_options.
///
/// This is a wrapper around \a ilist_node_base whose main purpose is to
/// provide type safety: you can't insert nodes of \a ilist_node_impl into the
/// wrong \a simple_ilist or \a iplist.
template <class OptionsT>
class ilist_node_impl
    : OptionsT::node_base_type,
      public ilist_detail::node_parent_access<ilist_node_impl<OptionsT>,
                                              typename OptionsT::parent_ty> { … };

/// An intrusive list node.
///
/// A base class to enable membership in intrusive lists, including \a
/// simple_ilist, \a iplist, and \a ilist.  The first template parameter is the
/// \a value_type for the list.
///
/// An ilist node can be configured with compile-time options to change
/// behaviour and/or add API.
///
/// By default, an \a ilist_node knows whether it is the list sentinel (an
/// instance of \a ilist_sentinel) if and only if
/// LLVM_ENABLE_ABI_BREAKING_CHECKS.  The function \a isKnownSentinel() always
/// returns \c false tracking is off.  Sentinel tracking steals a bit from the
/// "prev" link, which adds a mask operation when decrementing an iterator, but
/// enables bug-finding assertions in \a ilist_iterator.
///
/// To turn sentinel tracking on all the time, pass in the
/// ilist_sentinel_tracking<true> template parameter.  This also enables the \a
/// isSentinel() function.  The same option must be passed to the intrusive
/// list.  (ilist_sentinel_tracking<false> turns sentinel tracking off all the
/// time.)
///
/// A type can inherit from ilist_node multiple times by passing in different
/// \a ilist_tag options.  This allows a single instance to be inserted into
/// multiple lists simultaneously, where each list is given the same tag.
///
/// \example
/// struct A {};
/// struct B {};
/// struct N : ilist_node<N, ilist_tag<A>>, ilist_node<N, ilist_tag<B>> {};
///
/// void foo() {
///   simple_ilist<N, ilist_tag<A>> ListA;
///   simple_ilist<N, ilist_tag<B>> ListB;
///   N N1;
///   ListA.push_back(N1);
///   ListB.push_back(N1);
/// }
/// \endexample
///
/// When the \a ilist_parent<ParentTy> option is passed to an ilist_node and the
/// owning ilist, each node contains a pointer to the ilist's owner. This adds
/// \a getParent() and \a setParent(ParentTy*) methods to the ilist_node, which
/// will be used for node access by the ilist if the node class publicly
/// inherits from \a ilist_node_with_parent. By default, setParent() is not
/// automatically called by the ilist; a SymbolTableList will call setParent()
/// on inserted nodes, but the sentinel must still be manually set after the
/// list is created (e.g. SymTabList.end()->setParent(Parent)).
///
/// The primary benefit of using ilist_parent is that a parent
/// pointer will be stored in the sentinel, meaning that you can safely use \a
/// ilist_iterator::getNodeParent() to get the node parent from any valid (i.e.
/// non-null) iterator, even one that points to a sentinel value.
///
/// See \a is_valid_option for steps on adding a new option.
template <class T, class... Options>
class ilist_node
    : public ilist_node_impl<
          typename ilist_detail::compute_node_options<T, Options...>::type> { … };

namespace ilist_detail {

/// An access class for ilist_node private API.
///
/// This gives access to the private parts of ilist nodes.  Nodes for an ilist
/// should friend this class if they inherit privately from ilist_node.
///
/// Using this class outside of the ilist implementation is unsupported.
struct NodeAccess { … };

template <class OptionsT> struct SpecificNodeAccess : NodeAccess { … };

} // end namespace ilist_detail

template <class OptionsT>
class ilist_sentinel : public ilist_node_impl<OptionsT> { … };

/// An ilist node that can access its parent list.
///
/// Requires \c NodeTy to have \a getParent() to find the parent node, and the
/// \c ParentTy to have \a getSublistAccess() to get a reference to the list.
template <typename NodeTy, typename ParentTy, class... Options>
class ilist_node_with_parent : public ilist_node<NodeTy, Options...> { … };

} // end namespace llvm

#endif // LLVM_ADT_ILIST_NODE_H