GraphTraits.h revision e602f473062a91e6ac9aa17097de8b5cd75b0852
1//===-- llvm/ADT/GraphTraits.h - Graph traits template ----------*- 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 little GraphTraits<X> template class that should be
11// specialized by classes that want to be iteratable by generic graph iterators.
12//
13// This file also defines the marker class Inverse that is used to iterate over
14// graphs in a graph defined, inverse ordering...
15//
16//===----------------------------------------------------------------------===//
17
18#ifndef LLVM_ADT_GRAPHTRAITS_H
19#define LLVM_ADT_GRAPHTRAITS_H
20
21namespace llvm {
22
23// GraphTraits - This class should be specialized by different graph types...
24// which is why the default version is empty.
25//
26template<class GraphType>
27struct GraphTraits {
28  // Elements to provide:
29
30  // typedef NodeType          - Type of Node in the graph
31  // typedef ChildIteratorType - Type used to iterate over children in graph
32
33  // static NodeType *getEntryNode(const GraphType &)
34  //    Return the entry node of the graph
35
36  // static ChildIteratorType child_begin(NodeType *)
37  // static ChildIteratorType child_end  (NodeType *)
38  //    Return iterators that point to the beginning and ending of the child
39  //    node list for the specified node.
40  //
41
42
43  // typedef  ...iterator nodes_iterator;
44  // static nodes_iterator nodes_begin(GraphType *G)
45  // static nodes_iterator nodes_end  (GraphType *G)
46  //
47  //    nodes_iterator/begin/end - Allow iteration over all nodes in the graph
48
49
50  // If anyone tries to use this class without having an appropriate
51  // specialization, make an error.  If you get this error, it's because you
52  // need to include the appropriate specialization of GraphTraits<> for your
53  // graph, or you need to define it for a new graph type. Either that or
54  // your argument to XXX_begin(...) is unknown or needs to have the proper .h
55  // file #include'd.
56  //
57  typedef typename GraphType::UnknownGraphTypeError NodeType;
58};
59
60
61// Inverse - This class is used as a little marker class to tell the graph
62// iterator to iterate over the graph in a graph defined "Inverse" ordering.
63// Not all graphs define an inverse ordering, and if they do, it depends on
64// the graph exactly what that is.  Here's an example of usage with the
65// df_iterator:
66//
67// idf_iterator<Method*> I = idf_begin(M), E = idf_end(M);
68// for (; I != E; ++I) { ... }
69//
70// Which is equivalent to:
71// df_iterator<Inverse<Method*> > I = idf_begin(M), E = idf_end(M);
72// for (; I != E; ++I) { ... }
73//
74template <class GraphType>
75struct Inverse {
76  const GraphType &Graph;
77
78  inline Inverse(const GraphType &G) : Graph(G) {}
79};
80
81// Provide a partial specialization of GraphTraits so that the inverse of an
82// inverse falls back to the original graph.
83template<class T>
84struct GraphTraits<Inverse<Inverse<T> > > {
85  typedef typename GraphTraits<T>::NodeType NodeType;
86  typedef typename GraphTraits<T>::ChildIteratorType ChildIteratorType;
87
88  static NodeType *getEntryNode(Inverse<Inverse<T> > *G) {
89    return GraphTraits<T>::getEntryNode(G->Graph.Graph);
90  }
91
92  static ChildIteratorType child_begin(NodeType* N) {
93    return GraphTraits<T>::child_begin(N);
94  }
95
96  static ChildIteratorType child_end(NodeType* N) {
97    return GraphTraits<T>::child_end(N);
98  }
99};
100
101} // End llvm namespace
102
103#endif
104