ImmutableMap.h

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//===--- ImmutableMap.h - Immutable (functional) map interface --*- 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 defines the ImmutableMap class.
///
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_ADT_IMMUTABLEMAP_H
#define LLVM_ADT_IMMUTABLEMAP_H
 
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableSet.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include <utility>
 
namespace llvm {
 
/// Traits class used by ImmutableMap. While both the first and second elements
/// in a pair are used to generate profile information, only the first element
/// (the key) is used by isEqual and isLess.
template <typename T, typename S>
struct ImutKeyValueInfo {
  using value_type = const std::pair<T,S>;
  using value_type_ref = const value_type&;
  using key_type = const T;
  using key_type_ref = const T&;
  using data_type = const S;
  using data_type_ref = const S&;
 
  static inline key_type_ref KeyOfValue(value_type_ref V) {
    return V.first;
  }
 
  static inline data_type_ref DataOfValue(value_type_ref V) {
    return V.second;
  }
 
  static inline bool isEqual(key_type_ref L, key_type_ref R) {
    return ImutContainerInfo<T>::isEqual(L,R);
  }
  static inline bool isLess(key_type_ref L, key_type_ref R) {
    return ImutContainerInfo<T>::isLess(L,R);
  }
 
  static inline bool isDataEqual(data_type_ref L, data_type_ref R) {
    return ImutContainerInfo<S>::isEqual(L,R);
  }
 
  static inline void Profile(FoldingSetNodeID& ID, value_type_ref V) {
    ImutContainerInfo<T>::Profile(ID, V.first);
    ImutContainerInfo<S>::Profile(ID, V.second);
  }
};
 
template <typename KeyT, typename ValT,
          typename ValInfo = ImutKeyValueInfo<KeyT, ValT>,
          bool Canonicalize = true>
class LLVM_ATTRIBUTE_WARN_UNUSED ImmutableMap {
public:
  using value_type = typename ValInfo::value_type;
  using value_type_ref = typename ValInfo::value_type_ref;
  using key_type = typename ValInfo::key_type;
  using key_type_ref = typename ValInfo::key_type_ref;
  using data_type = typename ValInfo::data_type;
  using data_type_ref = typename ValInfo::data_type_ref;
  using TreeTy = ImutAVLTree<ValInfo, Canonicalize>;
 
protected:
  IntrusiveRefCntPtr<TreeTy> Root;
 
public:
  /// Constructs a map from a pointer to a tree root.  In general one
  /// should use a Factory object to create maps instead of directly
  /// invoking the constructor, but there are cases where make this
  /// constructor public is useful.
  explicit ImmutableMap(const TreeTy *R) : Root(const_cast<TreeTy *>(R)) {}
 
  class Factory {
    typename TreeTy::Factory F;
 
  public:
    Factory() = default;
 
    Factory(BumpPtrAllocator &Alloc) : F(Alloc) {}
 
    Factory(const Factory &) = delete;
    Factory &operator=(const Factory &) = delete;
 
    ImmutableMap getEmptyMap() { return ImmutableMap(F.getEmptyTree()); }
 
    [[nodiscard]] ImmutableMap add(ImmutableMap Old, key_type_ref K,
                                   data_type_ref D) {
      TreeTy *T = F.add(Old.Root.get(), std::pair<key_type, data_type>(K, D));
      if constexpr (Canonicalize)
        return ImmutableMap(F.getCanonicalTree(T));
      else
        return ImmutableMap(T);
    }
 
    /// Merges \p A and \p B in a single traversal (see
    /// ImutAVLFactory::mergeTrees), sharing subtrees the two maps do not
    /// overlap. \p Combine(AElem, BElem) yields the stored element for a key;
    /// \p KeepUnmatched governs keys unique to one side. \p SkipShared returns
    /// a pointer-identical subtree unchanged in O(1); only pass true when the
    /// merge is idempotent (Combine(a, a) == a, e.g. a lattice join). This is
    /// more efficient than repeatedly adding \p B's entries to \p A when \p B
    /// is large. Only valid for non-canonicalizing factories (the bulk path
    /// does not canonicalize the nodes it creates). Does not short-circuit
    /// equal/empty operands or reorder by size; callers wanting those apply
    /// them first.
    template <typename CombineFn>
    [[nodiscard]] ImmutableMap mergeWith(ImmutableMap A, ImmutableMap B,
                                         CombineFn Combine, bool KeepUnmatched,
                                         bool SkipShared = false) {
      static_assert(!Canonicalize,
                    "mergeWith does not canonicalize the nodes it creates");
      return ImmutableMap(F.mergeTrees(A.Root.get(), B.Root.get(), Combine,
                                       KeepUnmatched, SkipShared));
    }
 
    [[nodiscard]] ImmutableMap remove(ImmutableMap Old, key_type_ref K) {
      TreeTy *T = F.remove(Old.Root.get(), K);
      if constexpr (Canonicalize)
        return ImmutableMap(F.getCanonicalTree(T));
      else
        return ImmutableMap(T);
    }
 
    typename TreeTy::Factory *getTreeFactory() const {
      return const_cast<typename TreeTy::Factory *>(&F);
    }
  };
 
  [[nodiscard]] bool contains(key_type_ref K) const {
    return Root ? Root->contains(K) : false;
  }
 
  /// Compares two maps for equality. For a canonicalizing factory, maps with
  /// equal contents share the same tree, so this is an O(1) pointer comparison
  /// (like ImmutableList); only maps created by the same factory may be
  /// compared. Otherwise it is a structural comparison.
  [[nodiscard]] bool operator==(const ImmutableMap &RHS) const {
    if constexpr (Canonicalize)
      return Root == RHS.Root;
    else
      return Root && RHS.Root ? Root->isEqual(*RHS.Root.get())
                              : Root == RHS.Root;
  }
 
  [[nodiscard]] bool operator!=(const ImmutableMap &RHS) const {
    if constexpr (Canonicalize)
      return Root != RHS.Root;
    else
      return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
                              : Root != RHS.Root;
  }
 
  [[nodiscard]] TreeTy *getRoot() const {
    if (Root) { Root->retain(); }
    return Root.get();
  }
 
  [[nodiscard]] TreeTy *getRootWithoutRetain() const { return Root.get(); }
 
  void manualRetain() {
    if (Root) Root->retain();
  }
 
  void manualRelease() {
    if (Root) Root->release();
  }
 
  [[nodiscard]] bool isEmpty() const { return !Root; }
 
public:
  //===--------------------------------------------------===//
  // For testing.
  //===--------------------------------------------------===//
 
  void verify() const { if (Root) Root->verify(); }
 
  //===--------------------------------------------------===//
  // Iterators.
  //===--------------------------------------------------===//
 
  class iterator : public ImutAVLValueIterator<ImmutableMap> {
    friend class ImmutableMap;
 
    iterator() = default;
    explicit iterator(TreeTy *Tree) : iterator::ImutAVLValueIterator(Tree) {}
 
  public:
    key_type_ref getKey() const { return (*this)->first; }
    data_type_ref getData() const { return (*this)->second; }
  };
 
  [[nodiscard]] iterator begin() const { return iterator(Root.get()); }
  [[nodiscard]] iterator end() const { return iterator(); }
 
  [[nodiscard]] data_type *lookup(key_type_ref K) const {
    if (Root) {
      TreeTy* T = Root->find(K);
      if (T) return &T->getValue().second;
    }
 
    return nullptr;
  }
 
  /// Returns the <key,value> pair in the ImmutableMap for which key is the
  /// highest in the ordering of keys in the map. This method returns NULL if
  /// the map is empty.
  [[nodiscard]] value_type *getMaxElement() const {
    return Root ? &(Root->getMaxElement()->getValue()) : nullptr;
  }
 
  //===--------------------------------------------------===//
  // Utility methods.
  //===--------------------------------------------------===//
 
  [[nodiscard]] unsigned getHeight() const {
    return Root ? Root->getHeight() : 0;
  }
 
  static inline void Profile(FoldingSetNodeID& ID, const ImmutableMap& M) {
    ID.AddPointer(M.Root.get());
  }
 
  inline void Profile(FoldingSetNodeID& ID) const {
    return Profile(ID,*this);
  }
};
 
// NOTE: This will possibly become the new implementation of ImmutableMap some day.
template <typename KeyT, typename ValT,
typename ValInfo = ImutKeyValueInfo<KeyT,ValT>>
class ImmutableMapRef {
public:
  using value_type = typename ValInfo::value_type;
  using value_type_ref = typename ValInfo::value_type_ref;
  using key_type = typename ValInfo::key_type;
  using key_type_ref = typename ValInfo::key_type_ref;
  using data_type = typename ValInfo::data_type;
  using data_type_ref = typename ValInfo::data_type_ref;
  using TreeTy = ImutAVLTree<ValInfo>;
  using FactoryTy = typename TreeTy::Factory;
 
protected:
  IntrusiveRefCntPtr<TreeTy> Root;
  FactoryTy *Factory;
 
public:
  /// Constructs a map from a pointer to a tree root.  In general one
  /// should use a Factory object to create maps instead of directly
  /// invoking the constructor, but there are cases where make this
  /// constructor public is useful.
  ImmutableMapRef(const TreeTy *R, FactoryTy *F)
      : Root(const_cast<TreeTy *>(R)), Factory(F) {}
 
  ImmutableMapRef(const ImmutableMap<KeyT, ValT> &X,
                  typename ImmutableMap<KeyT, ValT>::Factory &F)
      : Root(X.getRootWithoutRetain()), Factory(F.getTreeFactory()) {}
 
  static inline ImmutableMapRef getEmptyMap(FactoryTy *F) {
    return ImmutableMapRef(nullptr, F);
  }
 
  void manualRetain() {
    if (Root) Root->retain();
  }
 
  void manualRelease() {
    if (Root) Root->release();
  }
 
  ImmutableMapRef add(key_type_ref K, data_type_ref D) const {
    TreeTy *NewT =
        Factory->add(Root.get(), std::pair<key_type, data_type>(K, D));
    return ImmutableMapRef(NewT, Factory);
  }
 
  ImmutableMapRef remove(key_type_ref K) const {
    TreeTy *NewT = Factory->remove(Root.get(), K);
    return ImmutableMapRef(NewT, Factory);
  }
 
  [[nodiscard]] bool contains(key_type_ref K) const {
    return Root ? Root->contains(K) : false;
  }
 
  ImmutableMap<KeyT, ValT> asImmutableMap() const {
    return ImmutableMap<KeyT, ValT>(Factory->getCanonicalTree(Root.get()));
  }
 
  [[nodiscard]] bool operator==(const ImmutableMapRef &RHS) const {
    return Root && RHS.Root ? Root->isEqual(*RHS.Root.get()) : Root == RHS.Root;
  }
 
  [[nodiscard]] bool operator!=(const ImmutableMapRef &RHS) const {
    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
                            : Root != RHS.Root;
  }
 
  [[nodiscard]] bool isEmpty() const { return !Root; }
 
  //===--------------------------------------------------===//
  // For testing.
  //===--------------------------------------------------===//
 
  void verify() const {
    if (Root)
      Root->verify();
  }
 
  //===--------------------------------------------------===//
  // Iterators.
  //===--------------------------------------------------===//
 
  class iterator : public ImutAVLValueIterator<ImmutableMapRef> {
    friend class ImmutableMapRef;
 
    iterator() = default;
    explicit iterator(TreeTy *Tree) : iterator::ImutAVLValueIterator(Tree) {}
 
  public:
    key_type_ref getKey() const { return (*this)->first; }
    data_type_ref getData() const { return (*this)->second; }
  };
 
  [[nodiscard]] iterator begin() const { return iterator(Root.get()); }
  [[nodiscard]] iterator end() const { return iterator(); }
 
  [[nodiscard]] data_type *lookup(key_type_ref K) const {
    if (Root) {
      TreeTy* T = Root->find(K);
      if (T) return &T->getValue().second;
    }
 
    return nullptr;
  }
 
  /// Returns the <key,value> pair in the ImmutableMap for which key is the
  /// highest in the ordering of keys in the map.  This method returns NULL if
  /// the map is empty.
  [[nodiscard]] value_type *getMaxElement() const {
    return Root ? &(Root->getMaxElement()->getValue()) : nullptr;
  }
 
  //===--------------------------------------------------===//
  // Utility methods.
  //===--------------------------------------------------===//
 
  [[nodiscard]] unsigned getHeight() const {
    return Root ? Root->getHeight() : 0;
  }
 
  static inline void Profile(FoldingSetNodeID &ID, const ImmutableMapRef &M) {
    ID.AddPointer(M.Root.get());
  }
 
  inline void Profile(FoldingSetNodeID &ID) const { return Profile(ID, *this); }
};
 
} // end namespace llvm
 
#endif // LLVM_ADT_IMMUTABLEMAP_H