include/llvm/ADT/UniqueVector.h

   1 //===- llvm/ADT/UniqueVector.h ----------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_ADT_UNIQUEVECTOR_H
  10 #define LLVM_ADT_UNIQUEVECTOR_H
  11
  12 #include <cassert>
  13 #include <cstddef>
  14 #include <map>
  15 #include <vector>
  16
  17 namespace llvm {
  18
  19 //===----------------------------------------------------------------------===//
  20 /// UniqueVector - This class produces a sequential ID number (base 1) for each
  21 /// unique entry that is added.  T is the type of entries in the vector. This
  22 /// class should have an implementation of operator== and of operator<.
  23 /// Entries can be fetched using operator[] with the entry ID.
  24 template<class T> class UniqueVector {
  25 public:
  26   using VectorType = typename std::vector<T>;
  27   using iterator = typename VectorType::iterator;
  28   using const_iterator = typename VectorType::const_iterator;
  29
  30 private:
  31   // Map - Used to handle the correspondence of entry to ID.
  32   std::map<T, unsigned> Map;
  33
  34   // Vector - ID ordered vector of entries. Entries can be indexed by ID - 1.
  35   VectorType Vector;
  36
  37 public:
  38   /// insert - Append entry to the vector if it doesn't already exist.  Returns
  39   /// the entry's index + 1 to be used as a unique ID.
  40   unsigned insert(const T &Entry) {
  41     // Check if the entry is already in the map.
  42     unsigned &Val = Map[Entry];
  43
  44     // See if entry exists, if so return prior ID.
  45     if (Val) return Val;
  46
  47     // Compute ID for entry.
  48     Val = static_cast<unsigned>(Vector.size()) + 1;
  49
  50     // Insert in vector.
  51     Vector.push_back(Entry);
  52     return Val;
  53   }
  54
  55   /// idFor - return the ID for an existing entry.  Returns 0 if the entry is
  56   /// not found.
  57   unsigned idFor(const T &Entry) const {
  58     // Search for entry in the map.
  59     typename std::map<T, unsigned>::const_iterator MI = Map.find(Entry);
  60
  61     // See if entry exists, if so return ID.
  62     if (MI != Map.end()) return MI->second;
  63
  64     // No luck.
  65     return 0;
  66   }
  67
  68   /// operator[] - Returns a reference to the entry with the specified ID.
  69   const T &operator[](unsigned ID) const {
  70     assert(ID-1 < size() && "ID is 0 or out of range!");
  71     return Vector[ID - 1];
  72   }
  73
  74   /// Return an iterator to the start of the vector.
  75   iterator begin() { return Vector.begin(); }
  76
  77   /// Return an iterator to the start of the vector.
  78   const_iterator begin() const { return Vector.begin(); }
  79
  80   /// Return an iterator to the end of the vector.
  81   iterator end() { return Vector.end(); }
  82
  83   /// Return an iterator to the end of the vector.
  84   const_iterator end() const { return Vector.end(); }
  85
  86   /// size - Returns the number of entries in the vector.
  87   size_t size() const { return Vector.size(); }
  88
  89   /// empty - Returns true if the vector is empty.
  90   bool empty() const { return Vector.empty(); }
  91
  92   /// reset - Clears all the entries.
  93   void reset() {
  94     Map.clear();
  95     Vector.resize(0, 0);
  96   }
  97 };
  98
  99 } // end namespace llvm
 100
 101 #endif // LLVM_ADT_UNIQUEVECTOR_H