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      1 //==-- llvm/ADT/ilist_node.h - Intrusive Linked List Helper ------*- 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 // This file defines the ilist_node class template, which is a convenient
     11 // base class for creating classes that can be used with ilists.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_ADT_ILIST_NODE_H
     16 #define LLVM_ADT_ILIST_NODE_H
     17 
     18 namespace llvm {
     19 
     20 template<typename NodeTy>
     21 struct ilist_traits;
     22 template <typename NodeTy> struct ilist_embedded_sentinel_traits;
     23 template <typename NodeTy> struct ilist_half_embedded_sentinel_traits;
     24 
     25 /// ilist_half_node - Base class that provides prev services for sentinels.
     26 ///
     27 template<typename NodeTy>
     28 class ilist_half_node {
     29   friend struct ilist_traits<NodeTy>;
     30   friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
     31   NodeTy *Prev;
     32 protected:
     33   NodeTy *getPrev() { return Prev; }
     34   const NodeTy *getPrev() const { return Prev; }
     35   void setPrev(NodeTy *P) { Prev = P; }
     36   ilist_half_node() : Prev(nullptr) {}
     37 };
     38 
     39 template<typename NodeTy>
     40 struct ilist_nextprev_traits;
     41 
     42 template <typename NodeTy> class ilist_iterator;
     43 
     44 /// ilist_node - Base class that provides next/prev services for nodes
     45 /// that use ilist_nextprev_traits or ilist_default_traits.
     46 ///
     47 template<typename NodeTy>
     48 class ilist_node : private ilist_half_node<NodeTy> {
     49   friend struct ilist_nextprev_traits<NodeTy>;
     50   friend struct ilist_traits<NodeTy>;
     51   friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
     52   friend struct ilist_embedded_sentinel_traits<NodeTy>;
     53   NodeTy *Next;
     54   NodeTy *getNext() { return Next; }
     55   const NodeTy *getNext() const { return Next; }
     56   void setNext(NodeTy *N) { Next = N; }
     57 protected:
     58   ilist_node() : Next(nullptr) {}
     59 
     60 public:
     61   ilist_iterator<NodeTy> getIterator() {
     62     // FIXME: Stop downcasting to create the iterator (potential UB).
     63     return ilist_iterator<NodeTy>(static_cast<NodeTy *>(this));
     64   }
     65   ilist_iterator<const NodeTy> getIterator() const {
     66     // FIXME: Stop downcasting to create the iterator (potential UB).
     67     return ilist_iterator<const NodeTy>(static_cast<const NodeTy *>(this));
     68   }
     69 };
     70 
     71 /// An ilist node that can access its parent list.
     72 ///
     73 /// Requires \c NodeTy to have \a getParent() to find the parent node, and the
     74 /// \c ParentTy to have \a getSublistAccess() to get a reference to the list.
     75 template <typename NodeTy, typename ParentTy>
     76 class ilist_node_with_parent : public ilist_node<NodeTy> {
     77 protected:
     78   ilist_node_with_parent() = default;
     79 
     80 private:
     81   /// Forward to NodeTy::getParent().
     82   ///
     83   /// Note: do not use the name "getParent()".  We want a compile error
     84   /// (instead of recursion) when the subclass fails to implement \a
     85   /// getParent().
     86   const ParentTy *getNodeParent() const {
     87     return static_cast<const NodeTy *>(this)->getParent();
     88   }
     89 
     90 public:
     91   /// @name Adjacent Node Accessors
     92   /// @{
     93   /// \brief Get the previous node, or \c nullptr for the list head.
     94   NodeTy *getPrevNode() {
     95     // Should be separated to a reused function, but then we couldn't use auto
     96     // (and would need the type of the list).
     97     const auto &List =
     98         getNodeParent()->*(ParentTy::getSublistAccess((NodeTy *)nullptr));
     99     return List.getPrevNode(*static_cast<NodeTy *>(this));
    100   }
    101   /// \brief Get the previous node, or \c nullptr for the list head.
    102   const NodeTy *getPrevNode() const {
    103     return const_cast<ilist_node_with_parent *>(this)->getPrevNode();
    104   }
    105 
    106   /// \brief Get the next node, or \c nullptr for the list tail.
    107   NodeTy *getNextNode() {
    108     // Should be separated to a reused function, but then we couldn't use auto
    109     // (and would need the type of the list).
    110     const auto &List =
    111         getNodeParent()->*(ParentTy::getSublistAccess((NodeTy *)nullptr));
    112     return List.getNextNode(*static_cast<NodeTy *>(this));
    113   }
    114   /// \brief Get the next node, or \c nullptr for the list tail.
    115   const NodeTy *getNextNode() const {
    116     return const_cast<ilist_node_with_parent *>(this)->getNextNode();
    117   }
    118   /// @}
    119 };
    120 
    121 } // End llvm namespace
    122 
    123 #endif
    124