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//===- llvm/ADT/MapVector.h - Map w/ deterministic value order --*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

///

/// \file

/// This file implements a map that provides insertion order iteration. The

/// interface is purposefully minimal. The key is assumed to be cheap to copy

/// and 2 copies are kept, one for indexing in a DenseMap, one for iteration in

/// a std::vector.

///

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_MAPVECTOR_H

#define LLVM_ADT_MAPVECTOR_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/SmallVector.h"

#include <cassert>

#include <cstddef>

#include <iterator>

#include <type_traits>

#include <utility>

#include <vector>

namespace llvm {

/// This class implements a map that also provides access to all stored values

/// in a deterministic order. The values are kept in a std::vector and the

/// mapping is done with DenseMap from Keys to indexes in that vector.

template<typename KeyT, typename ValueT,

         typename MapType = DenseMap<KeyT, unsigned>,

         typename VectorType = std::vector<std::pair<KeyT, ValueT>>>

class MapVector {

  MapType Map;

  VectorType Vector;

  static_assert(

      std::is_integral_v<typename MapType::mapped_type>,

      "The mapped_type of the specified Map must be an integral type");

public:

  using key_type = KeyT;

  using value_type = typename VectorType::value_type;

  using size_type = typename VectorType::size_type;

  using iterator = typename VectorType::iterator;

  using const_iterator = typename VectorType::const_iterator;

  using reverse_iterator = typename VectorType::reverse_iterator;

  using const_reverse_iterator = typename VectorType::const_reverse_iterator;

  /// Clear the MapVector and return the underlying vector.

  VectorType takeVector() {

    Map.clear();

    return std::move(Vector);

  }

  size_type size() const { return Vector.size(); }

  /// Grow the MapVector so that it can contain at least \p NumEntries items

  /// before resizing again.

  void reserve(size_type NumEntries) {

    Map.reserve(NumEntries);

    Vector.reserve(NumEntries);

  }

  iterator begin() { return Vector.begin(); }

  const_iterator begin() const { return Vector.begin(); }

  iterator end() { return Vector.end(); }

  const_iterator end() const { return Vector.end(); }

  reverse_iterator rbegin() { return Vector.rbegin(); }

  const_reverse_iterator rbegin() const { return Vector.rbegin(); }

  reverse_iterator rend() { return Vector.rend(); }

  const_reverse_iterator rend() const { return Vector.rend(); }

  bool empty() const {

    return Vector.empty();

  }

  std::pair<KeyT, ValueT>       &front()       { return Vector.front(); }

  const std::pair<KeyT, ValueT> &front() const { return Vector.front(); }

  std::pair<KeyT, ValueT>       &back()        { return Vector.back(); }

  const std::pair<KeyT, ValueT> &back()  const { return Vector.back(); }

  void clear() {

    Map.clear();

    Vector.clear();

  }

  void swap(MapVector &RHS) {

    std::swap(Map, RHS.Map);

    std::swap(Vector, RHS.Vector);

  }

  ValueT &operator[](const KeyT &Key) {

    std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(Key, 0);

    std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);

    auto &I = Result.first->second;

    if (Result.second) {

      Vector.push_back(std::make_pair(Key, ValueT()));

      I = Vector.size() - 1;

    }

    return Vector[I].second;

  }

  // Returns a copy of the value.  Only allowed if ValueT is copyable.

  ValueT lookup(const KeyT &Key) const {

    static_assert(std::is_copy_constructible_v<ValueT>,

                  "Cannot call lookup() if ValueT is not copyable.");

    typename MapType::const_iterator Pos = Map.find(Key);

    return Pos == Map.end()? ValueT() : Vector[Pos->second].second;

  }

  std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {

    std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0);

    std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);

    auto &I = Result.first->second;

    if (Result.second) {

      Vector.push_back(std::make_pair(KV.first, KV.second));

      I = Vector.size() - 1;

      return std::make_pair(std::prev(end()), true);

    }

    return std::make_pair(begin() + I, false);

  }

  std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {

    // Copy KV.first into the map, then move it into the vector.

    std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0);

    std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);

    auto &I = Result.first->second;

    if (Result.second) {

      Vector.push_back(std::move(KV));

      I = Vector.size() - 1;

      return std::make_pair(std::prev(end()), true);

    }

    return std::make_pair(begin() + I, false);

  }

  size_type count(const KeyT &Key) const {

    typename MapType::const_iterator Pos = Map.find(Key);

    return Pos == Map.end()? 0 : 1;

  }

  iterator find(const KeyT &Key) {

    typename MapType::const_iterator Pos = Map.find(Key);

    return Pos == Map.end()? Vector.end() :

                            (Vector.begin() + Pos->second);

  }

  const_iterator find(const KeyT &Key) const {

    typename MapType::const_iterator Pos = Map.find(Key);

    return Pos == Map.end()? Vector.end() :

                            (Vector.begin() + Pos->second);

  }

  /// Remove the last element from the vector.

  void pop_back() {

    typename MapType::iterator Pos = Map.find(Vector.back().first);

    Map.erase(Pos);

    Vector.pop_back();

  }

  /// Remove the element given by Iterator.

  ///

  /// Returns an iterator to the element following the one which was removed,

  /// which may be end().

  ///

  /// \note This is a deceivingly expensive operation (linear time).  It's

  /// usually better to use \a remove_if() if possible.

  typename VectorType::iterator erase(typename VectorType::iterator Iterator) {

    Map.erase(Iterator->first);

    auto Next = Vector.erase(Iterator);

    if (Next == Vector.end())

      return Next;

    // Update indices in the map.

    size_t Index = Next - Vector.begin();

    for (auto &I : Map) {

      assert(I.second != Index && "Index was already erased!");

      if (I.second > Index)

        --I.second;

    }

    return Next;

  }

  /// Remove all elements with the key value Key.

  ///

  /// Returns the number of elements removed.

  size_type erase(const KeyT &Key) {

    auto Iterator = find(Key);

    if (Iterator == end())

      return 0;

    erase(Iterator);

    return 1;

  }

  /// Remove the elements that match the predicate.

  ///

  /// Erase all elements that match \c Pred in a single pass.  Takes linear

  /// time.

  template <class Predicate> void remove_if(Predicate Pred);

};

template <typename KeyT, typename ValueT, typename MapType, typename VectorType>

template <class Function>

void MapVector<KeyT, ValueT, MapType, VectorType>::remove_if(Function Pred) {

  auto O = Vector.begin();

  for (auto I = O, E = Vector.end(); I != E; ++I) {

    if (Pred(*I)) {

      // Erase from the map.

      Map.erase(I->first);

      continue;

    }

    if (I != O) {

      // Move the value and update the index in the map.

      *O = std::move(*I);

      Map[O->first] = O - Vector.begin();

    }

    ++O;

  }

  // Erase trailing entries in the vector.

  Vector.erase(O, Vector.end());

}

/// A MapVector that performs no allocations if smaller than a certain

/// size.

template <typename KeyT, typename ValueT, unsigned N>

struct SmallMapVector

    : MapVector<KeyT, ValueT, SmallDenseMap<KeyT, unsigned, N>,

                SmallVector<std::pair<KeyT, ValueT>, N>> {

};

} // end namespace llvm

#endif // LLVM_ADT_MAPVECTOR_H