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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <cstddef>
namespace vespalib {
namespace metrics {
/**
* Common implementation of an opaque handle identified only
* by a (64-bit) integer. Templated to avoid different concepts
* sharing a superclass.
**/
template <typename T>
class Handle {
private:
size_t _id;
constexpr Handle() : _id(0) {}
public:
explicit Handle(size_t id) : _id(id) {}
size_t id() const { return _id; }
static const Handle empty_handle;
};
template <typename T>
const Handle<T> Handle<T>::empty_handle;
template <typename T>
bool
operator< (const Handle<T> &a, const Handle<T> &b) noexcept
{
return a.id() < b.id();
}
template <typename T>
bool
operator> (const Handle<T> &a, const Handle<T> &b) noexcept
{
return a.id() > b.id();
}
template <typename T>
bool
operator== (const Handle<T> &a, const Handle<T> &b) noexcept
{
return a.id() == b.id();
}
template <typename T>
bool
operator!= (const Handle<T> &a, const Handle<T> &b) noexcept
{
return a.id() != b.id();
}
} // namespace vespalib::metrics
} // namespace vespalib
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