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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2022- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
/**
* @file ostream_containers.hpp
* @brief Coercion safe method to insert a container into an ostream
*
* The contained type T must be ostream'able
*/
#pragma once
#include <ostream>
namespace openvpn::C2os {
/**
* @brief New typename for holding the underlying container type
*
* Note also that C2os::Container could be extended by passing in optional arguments to
* the Container ctor that could adjust the formatting (e.g., different delimiter,
* curlies vs square brackets, etc.)
*
* @tparam C underlying container type
*/
template <typename C>
struct Container
{
explicit Container(const C &container)
: ref(container)
{
}
const C &ref;
};
/**
* @brief Provide an instance of C2os::Container<C> from the underlying container
*
* This is the only interface the consumer sees (but see cast_deref, below)
*
* @tparam C underlying container type (deduced from the container param)
* @param container instance of the underlying container
* @return const C2os::Container<C> instance
*/
template <typename C>
inline const auto cast(const C &container)
{
return Container<C>(container);
}
/**
* @brief overload ostream operator<< for the C2os::Container<C> type
*
* @tparam C underlying container type
* @param os ostream instance
* @param container instance of the underlying container
* @return std::ostream& param os
*/
template <typename C>
inline std::ostream &operator<<(std::ostream &os, const Container<C> &container)
{
constexpr char separator[] = ", ";
const char *delimiter = "";
os << "[";
for (const auto &e : container.ref)
{
os << delimiter << e;
delimiter = separator;
}
os << "]";
return os;
}
/**
* @brief same idea as C2os::Container<C>, above; importantly, with a different typename
*
* @tparam C underlying container type
*/
template <typename C>
struct PtrContainer : Container<C>
{
using Container<C>::Container;
};
/**
* @brief Provide an instance of C2os::PtrContainer<C> from the underlying container
*
* This is the only interface the consumer sees if he wants to dereference the contained
* type T \a before ostream'ing it
*
* @tparam C underlying container type (deduced from the container param)
* @param container instance of the underlying container
* @return const C2os::PtrContainer<C> instance
*/
template <typename C>
inline const auto cast_deref(const C &container)
{
return PtrContainer<C>(container);
}
/**
* @brief overload ostream operator<< for the C2os::PtrContainer<C> type
*
* @tparam C underlying container type
* @param os ostream instance
* @param container instance of the underlying container
* @return std::ostream& param os
*/
template <typename C>
inline std::ostream &operator<<(std::ostream &os, const PtrContainer<C> &container)
{
constexpr char separator[] = ", ";
const char *delimiter = "";
os << "[";
for (const auto &e : container.ref)
{
os << delimiter << *e;
delimiter = separator;
}
os << "]";
return os;
}
} // namespace openvpn::C2os
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