1//===- Any.h - Generic type erased holder of any type -----------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//  This file provides Any, a non-template class modeled in the spirit of
10//  std::any.  The idea is to provide a type-safe replacement for C's void*.
11//  It can hold a value of any copy-constructible copy-assignable type
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ADT_ANY_H
16#define LLVM_ADT_ANY_H
17
18#include "llvm/ADT/STLExtras.h"
19
20#include <cassert>
21#include <memory>
22#include <type_traits>
23
24namespace llvm {
25
26class Any {
27  template <typename T> struct TypeId { static const char Id; };
28
29  struct StorageBase {
30    virtual ~StorageBase() = default;
31    virtual std::unique_ptr<StorageBase> clone() const = 0;
32    virtual const void *id() const = 0;
33  };
34
35  template <typename T> struct StorageImpl : public StorageBase {
36    explicit StorageImpl(const T &Value) : Value(Value) {}
37
38    explicit StorageImpl(T &&Value) : Value(std::move(Value)) {}
39
40    std::unique_ptr<StorageBase> clone() const override {
41      return std::make_unique<StorageImpl<T>>(Value);
42    }
43
44    const void *id() const override { return &TypeId<T>::Id; }
45
46    T Value;
47
48  private:
49    StorageImpl &operator=(const StorageImpl &Other) = delete;
50    StorageImpl(const StorageImpl &Other) = delete;
51  };
52
53public:
54  Any() = default;
55
56  Any(const Any &Other)
57      : Storage(Other.Storage ? Other.Storage->clone() : nullptr) {}
58
59  // When T is Any or T is not copy-constructible we need to explicitly disable
60  // the forwarding constructor so that the copy constructor gets selected
61  // instead.
62  template <
63      typename T,
64      typename std::enable_if<
65          llvm::conjunction<
66              llvm::negation<std::is_same<typename std::decay<T>::type, Any>>,
67              // We also disable this overload when an `Any` object can be
68              // converted to the parameter type because in that case, this
69              // constructor may combine with that conversion during overload
70              // resolution for determining copy constructibility, and then
71              // when we try to determine copy constructibility below we may
72              // infinitely recurse. This is being evaluated by the standards
73              // committee as a potential DR in `std::any` as well, but we're
74              // going ahead and adopting it to work-around usage of `Any` with
75              // types that need to be implicitly convertible from an `Any`.
76              llvm::negation<std::is_convertible<Any, typename std::decay<T>::type>>,
77              std::is_copy_constructible<typename std::decay<T>::type>>::value,
78          int>::type = 0>
79  Any(T &&Value) {
80    using U = typename std::decay<T>::type;
81    Storage = std::make_unique<StorageImpl<U>>(std::forward<T>(Value));
82  }
83
84  Any(Any &&Other) : Storage(std::move(Other.Storage)) {}
85
86  Any &swap(Any &Other) {
87    std::swap(Storage, Other.Storage);
88    return *this;
89  }
90
91  Any &operator=(Any Other) {
92    Storage = std::move(Other.Storage);
93    return *this;
94  }
95
96  bool hasValue() const { return !!Storage; }
97
98  void reset() { Storage.reset(); }
99
100private:
101  template <class T> friend T any_cast(const Any &Value);
102  template <class T> friend T any_cast(Any &Value);
103  template <class T> friend T any_cast(Any &&Value);
104  template <class T> friend const T *any_cast(const Any *Value);
105  template <class T> friend T *any_cast(Any *Value);
106  template <typename T> friend bool any_isa(const Any &Value);
107
108  std::unique_ptr<StorageBase> Storage;
109};
110
111template <typename T> const char Any::TypeId<T>::Id = 0;
112
113
114template <typename T> bool any_isa(const Any &Value) {
115  if (!Value.Storage)
116    return false;
117  using U =
118      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
119  return Value.Storage->id() == &Any::TypeId<U>::Id;
120}
121
122template <class T> T any_cast(const Any &Value) {
123  using U =
124      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
125  return static_cast<T>(*any_cast<U>(&Value));
126}
127
128template <class T> T any_cast(Any &Value) {
129  using U =
130      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
131  return static_cast<T>(*any_cast<U>(&Value));
132}
133
134template <class T> T any_cast(Any &&Value) {
135  using U =
136      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
137  return static_cast<T>(std::move(*any_cast<U>(&Value)));
138}
139
140template <class T> const T *any_cast(const Any *Value) {
141  using U =
142      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
143  assert(Value && any_isa<T>(*Value) && "Bad any cast!");
144  if (!Value || !any_isa<U>(*Value))
145    return nullptr;
146  return &static_cast<Any::StorageImpl<U> &>(*Value->Storage).Value;
147}
148
149template <class T> T *any_cast(Any *Value) {
150  using U = typename std::decay<T>::type;
151  assert(Value && any_isa<U>(*Value) && "Bad any cast!");
152  if (!Value || !any_isa<U>(*Value))
153    return nullptr;
154  return &static_cast<Any::StorageImpl<U> &>(*Value->Storage).Value;
155}
156
157} // end namespace llvm
158
159#endif // LLVM_ADT_ANY_H
160