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/*
* Copyright 2017 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef WABT_CAST_H_
#define WABT_CAST_H_
#include <memory>
#include <type_traits>
#include "wabt/common.h"
// Modeled after LLVM's dynamic casts:
// http://llvm.org/docs/ProgrammersManual.html#the-isa-cast-and-dyn-cast-templates
//
// Use isa<T>(foo) to check whether foo is a T*:
//
// if (isa<Minivan>(car)) {
// ...
// }
//
// Use cast<T>(foo) when you know that foo is a T* -- it will assert that the
// type matches:
//
// switch (car.type) {
// case CarType::Minivan: {
// auto minivan = cast<Minivan>(car);
// ...
// }
// }
//
// Use dyn_cast<T>(foo) as a combination if isa and cast, it will return
// nullptr if the type doesn't match:
//
// if (auto minivan = dyn_cast<Minivan>(car)) {
// ...
// }
//
//
// To use these classes in a type hierarchy, you must implement classof:
//
// enum CarType { Minivan, ... };
// struct Car { CarType type; ... };
// struct Minivan : Car {
// static bool classof(const Car* car) { return car->type == Minivan; }
// ...
// };
//
namespace wabt {
template <typename Derived, typename Base>
bool isa(const Base* base) {
WABT_STATIC_ASSERT((std::is_base_of<Base, Derived>::value));
return Derived::classof(base);
}
template <typename Derived, typename Base>
const Derived* cast(const Base* base) {
assert(isa<Derived>(base));
return static_cast<const Derived*>(base);
};
template <typename Derived, typename Base>
Derived* cast(Base* base) {
assert(isa<Derived>(base));
return static_cast<Derived*>(base);
};
template <typename Derived, typename Base>
const Derived* dyn_cast(const Base* base) {
return isa<Derived>(base) ? static_cast<const Derived*>(base) : nullptr;
};
template <typename Derived, typename Base>
Derived* dyn_cast(Base* base) {
return isa<Derived>(base) ? static_cast<Derived*>(base) : nullptr;
};
// Cast functionality for unique_ptr. isa and dyn_cast are not included because
// they won't always pass ownership back to the caller.
template <typename Derived, typename Base>
std::unique_ptr<const Derived> cast(std::unique_ptr<const Base>&& base) {
assert(isa<Derived>(base.get()));
return std::unique_ptr<Derived>(static_cast<const Derived*>(base.release()));
};
template <typename Derived, typename Base>
std::unique_ptr<Derived> cast(std::unique_ptr<Base>&& base) {
assert(isa<Derived>(base.get()));
return std::unique_ptr<Derived>(static_cast<Derived*>(base.release()));
};
} // namespace wabt
#endif // WABT_CAST_H_
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