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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_ILISTNODE_H
     16 #define LLVM_ADT_ILISTNODE_H
     17 
     18 namespace llvm {
     19 
     20 template<typename NodeTy>
     21 struct ilist_traits;
     22 
     23 /// ilist_half_node - Base class that provides prev services for sentinels.
     24 ///
     25 template<typename NodeTy>
     26 class ilist_half_node {
     27   friend struct ilist_traits<NodeTy>;
     28   NodeTy *Prev;
     29 protected:
     30   NodeTy *getPrev() { return Prev; }
     31   const NodeTy *getPrev() const { return Prev; }
     32   void setPrev(NodeTy *P) { Prev = P; }
     33   ilist_half_node() : Prev(0) {}
     34 };
     35 
     36 template<typename NodeTy>
     37 struct ilist_nextprev_traits;
     38 
     39 /// ilist_node - Base class that provides next/prev services for nodes
     40 /// that use ilist_nextprev_traits or ilist_default_traits.
     41 ///
     42 template<typename NodeTy>
     43 class ilist_node : private ilist_half_node<NodeTy> {
     44   friend struct ilist_nextprev_traits<NodeTy>;
     45   friend struct ilist_traits<NodeTy>;
     46   NodeTy *Next;
     47   NodeTy *getNext() { return Next; }
     48   const NodeTy *getNext() const { return Next; }
     49   void setNext(NodeTy *N) { Next = N; }
     50 protected:
     51   ilist_node() : Next(0) {}
     52 
     53 public:
     54   /// @name Adjacent Node Accessors
     55   /// @{
     56 
     57   /// \brief Get the previous node, or 0 for the list head.
     58   NodeTy *getPrevNode() {
     59     NodeTy *Prev = this->getPrev();
     60 
     61     // Check for sentinel.
     62     if (!Prev->getNext())
     63       return 0;
     64 
     65     return Prev;
     66   }
     67 
     68   /// \brief Get the previous node, or 0 for the list head.
     69   const NodeTy *getPrevNode() const {
     70     const NodeTy *Prev = this->getPrev();
     71 
     72     // Check for sentinel.
     73     if (!Prev->getNext())
     74       return 0;
     75 
     76     return Prev;
     77   }
     78 
     79   /// \brief Get the next node, or 0 for the list tail.
     80   NodeTy *getNextNode() {
     81     NodeTy *Next = getNext();
     82 
     83     // Check for sentinel.
     84     if (!Next->getNext())
     85       return 0;
     86 
     87     return Next;
     88   }
     89 
     90   /// \brief Get the next node, or 0 for the list tail.
     91   const NodeTy *getNextNode() const {
     92     const NodeTy *Next = getNext();
     93 
     94     // Check for sentinel.
     95     if (!Next->getNext())
     96       return 0;
     97 
     98     return Next;
     99   }
    100 
    101   /// @}
    102 };
    103 
    104 } // End llvm namespace
    105 
    106 #endif
    107