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//==--- ImmutableList.h - Immutable (functional) list 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 // //===----------------------------------------------------------------------===// // // This file defines the ImmutableList class. // //===----------------------------------------------------------------------===// #ifndef LLVM_ADT_IMMUTABLELIST_H #define LLVM_ADT_IMMUTABLELIST_H #include "llvm/ADT/FoldingSet.h" #include "llvm/Support/Allocator.h" #include <cassert> #include <cstdint> #include <new> namespace llvm { template <typename T> class ImmutableListFactory; template <typename T> class ImmutableListImpl : public FoldingSetNode { friend class ImmutableListFactory<T>; T Head; const ImmutableListImpl* Tail; template <typename ElemT> ImmutableListImpl(ElemT &&head, const ImmutableListImpl *tail = nullptr) : Head(std::forward<ElemT>(head)), Tail(tail) {} public: ImmutableListImpl(const ImmutableListImpl &) = delete; ImmutableListImpl &operator=(const ImmutableListImpl &) = delete; const T& getHead() const { return Head; } const ImmutableListImpl* getTail() const { return Tail; } static inline void Profile(FoldingSetNodeID& ID, const T& H, const ImmutableListImpl* L){ ID.AddPointer(L); ID.Add(H); } void Profile(FoldingSetNodeID& ID) { Profile(ID, Head, Tail); } }; /// ImmutableList - This class represents an immutable (functional) list. /// It is implemented as a smart pointer (wraps ImmutableListImpl), so it /// it is intended to always be copied by value as if it were a pointer. /// This interface matches ImmutableSet and ImmutableMap. ImmutableList /// objects should almost never be created directly, and instead should /// be created by ImmutableListFactory objects that manage the lifetime /// of a group of lists. When the factory object is reclaimed, all lists /// created by that factory are released as well. template <typename T> class ImmutableList { public: using value_type = T; using Factory = ImmutableListFactory<T>; static_assert(std::is_trivially_destructible<T>::value, "T must be trivially destructible!"); private: const ImmutableListImpl<T>* X; public: // This constructor should normally only be called by ImmutableListFactory<T>. // There may be cases, however, when one needs to extract the internal pointer // and reconstruct a list object from that pointer. ImmutableList(const ImmutableListImpl<T>* x = nullptr) : X(x) {} const ImmutableListImpl<T>* getInternalPointer() const { return X; } class iterator { const ImmutableListImpl<T>* L = nullptr; public: iterator() = default; iterator(ImmutableList l) : L(l.getInternalPointer()) {} iterator& operator++() { L = L->getTail(); return *this; } bool operator==(const iterator& I) const { return L == I.L; } bool operator!=(const iterator& I) const { return L != I.L; } const value_type& operator*() const { return L->getHead(); } const typename std::remove_reference<value_type>::type* operator->() const { return &L->getHead(); } ImmutableList getList() const { return L; } }; /// begin - Returns an iterator referring to the head of the list, or /// an iterator denoting the end of the list if the list is empty. iterator begin() const { return iterator(X); } /// end - Returns an iterator denoting the end of the list. This iterator /// does not refer to a valid list element. iterator end() const { return iterator(); } /// isEmpty - Returns true if the list is empty. bool isEmpty() const { return !X; } bool contains(const T& V) const { for (iterator I = begin(), E = end(); I != E; ++I) { if (*I == V) return true; } return false; } /// isEqual - Returns true if two lists are equal. Because all lists created /// from the same ImmutableListFactory are uniqued, this has O(1) complexity /// because it the contents of the list do not need to be compared. Note /// that you should only compare two lists created from the same /// ImmutableListFactory. bool isEqual(const ImmutableList& L) const { return X == L.X; } bool operator==(const ImmutableList& L) const { return isEqual(L); } /// getHead - Returns the head of the list. const T& getHead() const { assert(!isEmpty() && "Cannot get the head of an empty list."); return X->getHead(); } /// getTail - Returns the tail of the list, which is another (possibly empty) /// ImmutableList. ImmutableList getTail() const { return X ? X->getTail() : nullptr; } void Profile(FoldingSetNodeID& ID) const { ID.AddPointer(X); } }; template <typename T> class ImmutableListFactory { using ListTy = ImmutableListImpl<T>; using CacheTy = FoldingSet<ListTy>; CacheTy Cache; uintptr_t Allocator; bool ownsAllocator() const { return (Allocator & 0x1) == 0; } BumpPtrAllocator& getAllocator() const { return *reinterpret_cast<BumpPtrAllocator*>(Allocator & ~0x1); } public: ImmutableListFactory() : Allocator(reinterpret_cast<uintptr_t>(new BumpPtrAllocator())) {} ImmutableListFactory(BumpPtrAllocator& Alloc) : Allocator(reinterpret_cast<uintptr_t>(&Alloc) | 0x1) {} ~ImmutableListFactory() { if (ownsAllocator()) delete &getAllocator(); } template <typename ElemT> LLVM_NODISCARD ImmutableList<T> concat(ElemT &&Head, ImmutableList<T> Tail) { // Profile the new list to see if it already exists in our cache. FoldingSetNodeID ID; void* InsertPos; const ListTy* TailImpl = Tail.getInternalPointer(); ListTy::Profile(ID, Head, TailImpl); ListTy* L = Cache.FindNodeOrInsertPos(ID, InsertPos); if (!L) { // The list does not exist in our cache. Create it. BumpPtrAllocator& A = getAllocator(); L = (ListTy*) A.Allocate<ListTy>(); new (L) ListTy(std::forward<ElemT>(Head), TailImpl); // Insert the new list into the cache. Cache.InsertNode(L, InsertPos); } return L; } template <typename ElemT> LLVM_NODISCARD ImmutableList<T> add(ElemT &&Data, ImmutableList<T> L) { return concat(std::forward<ElemT>(Data), L); } template <typename ...CtorArgs> LLVM_NODISCARD ImmutableList<T> emplace(ImmutableList<T> Tail, CtorArgs &&...Args) { return concat(T(std::forward<CtorArgs>(Args)...), Tail); } ImmutableList<T> getEmptyList() const { return ImmutableList<T>(nullptr); } template <typename ElemT> ImmutableList<T> create(ElemT &&Data) { return concat(std::forward<ElemT>(Data), getEmptyList()); } }; //===----------------------------------------------------------------------===// // Partially-specialized Traits. //===----------------------------------------------------------------------===// template<typename T> struct DenseMapInfo; template<typename T> struct DenseMapInfo<ImmutableList<T>> { static inline ImmutableList<T> getEmptyKey() { return reinterpret_cast<ImmutableListImpl<T>*>(-1); } static inline ImmutableList<T> getTombstoneKey() { return reinterpret_cast<ImmutableListImpl<T>*>(-2); } static unsigned getHashValue(ImmutableList<T> X) { uintptr_t PtrVal = reinterpret_cast<uintptr_t>(X.getInternalPointer()); return (unsigned((uintptr_t)PtrVal) >> 4) ^ (unsigned((uintptr_t)PtrVal) >> 9); } static bool isEqual(ImmutableList<T> X1, ImmutableList<T> X2) { return X1 == X2; } }; } // end namespace llvm #endif // LLVM_ADT_IMMUTABLELIST_H