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//===- Any.h - Generic type erased holder of any type -----------*- 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 provides Any, a non-template class modeled in the spirit of // std::any. The idea is to provide a type-safe replacement for C's void*. // It can hold a value of any copy-constructible copy-assignable type // //===----------------------------------------------------------------------===// #ifndef LLVM_ADT_ANY_H #define LLVM_ADT_ANY_H #include "llvm/ADT/STLExtras.h" #include <cassert> #include <memory> #include <type_traits> namespace llvm { class Any { template <typename T> struct TypeId { static const char Id; }; struct StorageBase { virtual ~StorageBase() = default; virtual std::unique_ptr<StorageBase> clone() const = 0; virtual const void *id() const = 0; }; template <typename T> struct StorageImpl : public StorageBase { explicit StorageImpl(const T &Value) : Value(Value) {} explicit StorageImpl(T &&Value) : Value(std::move(Value)) {} std::unique_ptr<StorageBase> clone() const override { return std::make_unique<StorageImpl<T>>(Value); } const void *id() const override { return &TypeId<T>::Id; } T Value; private: StorageImpl &operator=(const StorageImpl &Other) = delete; StorageImpl(const StorageImpl &Other) = delete; }; public: Any() = default; Any(const Any &Other) : Storage(Other.Storage ? Other.Storage->clone() : nullptr) {} // When T is Any or T is not copy-constructible we need to explicitly disable // the forwarding constructor so that the copy constructor gets selected // instead. template < typename T, typename std::enable_if< llvm::conjunction< llvm::negation<std::is_same<typename std::decay<T>::type, Any>>, // We also disable this overload when an `Any` object can be // converted to the parameter type because in that case, this // constructor may combine with that conversion during overload // resolution for determining copy constructibility, and then // when we try to determine copy constructibility below we may // infinitely recurse. This is being evaluated by the standards // committee as a potential DR in `std::any` as well, but we're // going ahead and adopting it to work-around usage of `Any` with // types that need to be implicitly convertible from an `Any`. llvm::negation<std::is_convertible<Any, typename std::decay<T>::type>>, std::is_copy_constructible<typename std::decay<T>::type>>::value, int>::type = 0> Any(T &&Value) { using U = typename std::decay<T>::type; Storage = std::make_unique<StorageImpl<U>>(std::forward<T>(Value)); } Any(Any &&Other) : Storage(std::move(Other.Storage)) {} Any &swap(Any &Other) { std::swap(Storage, Other.Storage); return *this; } Any &operator=(Any Other) { Storage = std::move(Other.Storage); return *this; } bool hasValue() const { return !!Storage; } void reset() { Storage.reset(); } private: template <class T> friend T any_cast(const Any &Value); template <class T> friend T any_cast(Any &Value); template <class T> friend T any_cast(Any &&Value); template <class T> friend const T *any_cast(const Any *Value); template <class T> friend T *any_cast(Any *Value); template <typename T> friend bool any_isa(const Any &Value); std::unique_ptr<StorageBase> Storage; }; template <typename T> const char Any::TypeId<T>::Id = 0; template <typename T> bool any_isa(const Any &Value) { if (!Value.Storage) return false; using U = typename std::remove_cv<typename std::remove_reference<T>::type>::type; return Value.Storage->id() == &Any::TypeId<U>::Id; } template <class T> T any_cast(const Any &Value) { using U = typename std::remove_cv<typename std::remove_reference<T>::type>::type; return static_cast<T>(*any_cast<U>(&Value)); } template <class T> T any_cast(Any &Value) { using U = typename std::remove_cv<typename std::remove_reference<T>::type>::type; return static_cast<T>(*any_cast<U>(&Value)); } template <class T> T any_cast(Any &&Value) { using U = typename std::remove_cv<typename std::remove_reference<T>::type>::type; return static_cast<T>(std::move(*any_cast<U>(&Value))); } template <class T> const T *any_cast(const Any *Value) { using U = typename std::remove_cv<typename std::remove_reference<T>::type>::type; assert(Value && any_isa<T>(*Value) && "Bad any cast!"); if (!Value || !any_isa<U>(*Value)) return nullptr; return &static_cast<Any::StorageImpl<U> &>(*Value->Storage).Value; } template <class T> T *any_cast(Any *Value) { using U = typename std::decay<T>::type; assert(Value && any_isa<U>(*Value) && "Bad any cast!"); if (!Value || !any_isa<U>(*Value)) return nullptr; return &static_cast<Any::StorageImpl<U> &>(*Value->Storage).Value; } } // end namespace llvm #endif // LLVM_ADT_ANY_H