llvm/ADT/UniqueVector.h

0001 //===- llvm/ADT/UniqueVector.h ----------------------------------*- C++ -*-===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef LLVM_ADT_UNIQUEVECTOR_H
0010 #define LLVM_ADT_UNIQUEVECTOR_H
0011
0012 #include <cassert>
0013 #include <cstddef>
0014 #include <map>
0015 #include <vector>
0016
0017 namespace llvm {
0018
0019 //===----------------------------------------------------------------------===//
0020 /// UniqueVector - This class produces a sequential ID number (base 1) for each
0021 /// unique entry that is added.  T is the type of entries in the vector. This
0022 /// class should have an implementation of operator== and of operator<.
0023 /// Entries can be fetched using operator[] with the entry ID.
0024 template<class T> class UniqueVector {
0025 public:
0026   using VectorType = typename std::vector<T>;
0027   using iterator = typename VectorType::iterator;
0028   using const_iterator = typename VectorType::const_iterator;
0029
0030 private:
0031   // Map - Used to handle the correspondence of entry to ID.
0032   std::map<T, unsigned> Map;
0033
0034   // Vector - ID ordered vector of entries. Entries can be indexed by ID - 1.
0035   VectorType Vector;
0036
0037 public:
0038   /// insert - Append entry to the vector if it doesn't already exist.  Returns
0039   /// the entry's index + 1 to be used as a unique ID.
0040   unsigned insert(const T &Entry) {
0041     // Check if the entry is already in the map.
0042     unsigned &Val = Map[Entry];
0043
0044     // See if entry exists, if so return prior ID.
0045     if (Val) return Val;
0046
0047     // Compute ID for entry.
0048     Val = static_cast<unsigned>(Vector.size()) + 1;
0049
0050     // Insert in vector.
0051     Vector.push_back(Entry);
0052     return Val;
0053   }
0054
0055   /// idFor - return the ID for an existing entry.  Returns 0 if the entry is
0056   /// not found.
0057   unsigned idFor(const T &Entry) const {
0058     // Search for entry in the map.
0059     typename std::map<T, unsigned>::const_iterator MI = Map.find(Entry);
0060
0061     // See if entry exists, if so return ID.
0062     if (MI != Map.end()) return MI->second;
0063
0064     // No luck.
0065     return 0;
0066   }
0067
0068   /// operator[] - Returns a reference to the entry with the specified ID.
0069   const T &operator[](unsigned ID) const {
0070     assert(ID-1 < size() && "ID is 0 or out of range!");
0071     return Vector[ID - 1];
0072   }
0073
0074   /// Return an iterator to the start of the vector.
0075   iterator begin() { return Vector.begin(); }
0076
0077   /// Return an iterator to the start of the vector.
0078   const_iterator begin() const { return Vector.begin(); }
0079
0080   /// Return an iterator to the end of the vector.
0081   iterator end() { return Vector.end(); }
0082
0083   /// Return an iterator to the end of the vector.
0084   const_iterator end() const { return Vector.end(); }
0085
0086   /// size - Returns the number of entries in the vector.
0087   size_t size() const { return Vector.size(); }
0088
0089   /// empty - Returns true if the vector is empty.
0090   bool empty() const { return Vector.empty(); }
0091
0092   /// reset - Clears all the entries.
0093   void reset() {
0094     Map.clear();
0095     Vector.resize(0, 0);
0096   }
0097 };
0098
0099 } // end namespace llvm
0100
0101 #endif // LLVM_ADT_UNIQUEVECTOR_H