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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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// 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 std::remove_reference_t<value_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>
[[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>
[[nodiscard]] ImmutableList<T> add(ElemT &&Data, ImmutableList<T> L) {
return concat(std::forward<ElemT>(Data), L);
}
template <typename... CtorArgs>
[[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<ImmutableList<T>, void> {
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
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