Import MapVector from LLVM. (#1128)

wpiutil/.styleguide

@@ -22,6 +22,7 @@ generatedFileExclude {
   src/main/native/include/wpi/Format\.h$
   src/main/native/include/wpi/Hashing\.h$
   src/main/native/include/wpi/IntrusiveRefCntPtr\.h$
+  src/main/native/include/wpi/MapVector\.h$
   src/main/native/include/wpi/MathExtras\.h$
   src/main/native/include/wpi/NativeFormatting\.h$
   src/main/native/include/wpi/None\.h$

wpiutil/src/main/native/include/wpi/MapVector.h

@@ -0,0 +1,240 @@
+//===- llvm/ADT/MapVector.h - Map w/ deterministic value order --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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 WPIUTIL_WPI_MAPVECTOR_H
+#define WPIUTIL_WPI_MAPVECTOR_H
+
+#include "wpi/DenseMap.h"
+#include "wpi/SmallVector.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <iterator>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+namespace wpi {
+
+/// 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<typename MapType::mapped_type>::value,
+      "The mapped_type of the specified Map must be an integral type");
+
+public:
+  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<ValueT>::value,
+                  "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 wpi
+
+#endif // LLVM_ADT_MAPVECTOR_H