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/*
* Copyright (C) 2017 The Android Open Source Project
*
* 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 NETUTILS_HANDLE_H
#define NETUTILS_HANDLE_H
#include <ostream>
namespace android {
namespace netdutils {
// Opaque, strongly typed wrapper for integer-like handles.
// Explicitly avoids implementing arithmetic operations.
//
// This class is intended to avoid common errors when reordering
// arguments to functions, typos and other cases where plain integer
// types would silently cover up the mistake.
//
// usage:
// DEFINE_HANDLE(ProductId, uint64_t);
// DEFINE_HANDLE(ThumbnailHash, uint64_t);
// void foo(ProductId p, ThumbnailHash th) {...}
//
// void test() {
// ProductId p(88);
// ThumbnailHash th1(100), th2(200);
//
// foo(p, th1); <- ok!
// foo(th1, p); <- disallowed!
// th1 += 10; <- disallowed!
// p = th2; <- disallowed!
// assert(th1 != th2); <- ok!
// }
template <typename T, typename TagT>
class Handle {
public:
constexpr Handle() = default;
constexpr Handle(const T& value) : mValue(value) {}
const T get() const { return mValue; }
bool operator==(const Handle& that) const { return get() == that.get(); }
bool operator!=(const Handle& that) const { return get() != that.get(); }
private:
T mValue;
};
#define DEFINE_HANDLE(name, type) \
struct _##name##Tag {}; \
using name = ::android::netdutils::Handle<type, _##name##Tag>;
template <typename T, typename TagT>
inline std::ostream& operator<<(std::ostream& os, const Handle<T, TagT>& handle) {
return os << handle.get();
}
} // namespace netdutils
} // namespace android
#endif /* NETUTILS_HANDLE_H */
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