UniqueVector template provides a means of enumerating objects uniquely.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25376 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/UniqueVector.h b/include/llvm/ADT/UniqueVector.h
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+
+//===-- llvm/ADT/UniqueVector.h ---------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by James M. Laskey and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_UNIQUEVECTOR_H
+#define LLVM_ADT_UNIQUEVECTOR_H
+
+#include <map>
+#include <vector>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+/// UniqueVector - This class produces a sequential ID number (base 1) for each
+/// unique entry that is added.  This class also provides an ID ordered vector
+/// of the entries (indexed by ID - 1.)  T is the type of entries in the vector.
+/// This class should have an implementation of operator== and of operator<.
+template<class T> class UniqueVector {
+private:
+  // Map - Used to handle the correspondence of entry to ID.
+  typename std::map<T, unsigned> Map;
+
+  // Vector - ID ordered vector of entries. Entries can be indexed by ID - 1.
+  //
+  typename std::vector<T> Vector;
+  
+public:
+  /// insert - Append entry to the vector if it doesn't already exist.  Returns
+  /// the entry's index + 1 to be used as a unique ID.
+  unsigned insert(const T &Entry) {
+    // Check if the entry is already in the map.
+    typename std::map<T, unsigned>::iterator MI = Map.lower_bound(Entry);
+    
+    // See if entry exists, if so return prior ID.
+    if (MI != Map.end() && MI->first == Entry) return MI->second;
+
+    // Compute ID for entry.
+    unsigned ID = Vector.size() + 1;
+    
+    // Insert in map.
+    Map.insert(MI, std::make_pair(Entry, ID));
+    
+    // Insert in vector.
+    Vector.push_back(Entry);
+
+    return ID;
+  }
+  
+  /// operator[] - Returns a reference to the entry with the specified ID.
+  /// 
+  const T &operator[](unsigned ID) const { return Vector[ID - 1]; }
+  
+  /// size - Returns the number of entries in the vector.
+  ///
+  size_t size() const { return Vector.size(); }
+  
+  /// getVector - Return the ID ordered vector of entries.
+  ///
+  inline const typename std::vector<T> &getVector() const { return Vector; }
+};
+
+} // End of namespace llvm
+
+#endif // LLVM_ADT_UNIQUEVECTOR_H
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