xbot/myirc/include/ref.hpp

#pragma once

#include <openssl/evp.h>
#include <openssl/x509.h>

#include <memory>

// Specializations must Free to release a reference
// Specializations can implement UpRef to increase a reference count on copy
template <typename> struct RefTraits {};

template <> struct RefTraits<EVP_PKEY> {
    static constexpr void (*Free)(EVP_PKEY*) = EVP_PKEY_free;
    static constexpr int (*UpRef)(EVP_PKEY*) = EVP_PKEY_up_ref;
};

template <> struct RefTraits<X509> {
    static constexpr void (*Free)(X509*) = X509_free;
    static constexpr int (*UpRef)(X509*) = X509_up_ref;
};

template <> struct RefTraits<EVP_PKEY_CTX> {
    static constexpr void (*Free)(EVP_PKEY_CTX*) = EVP_PKEY_CTX_free;
    // this type does not implement UpRef
};

template <typename T>
struct RefDeleter {
    auto operator()(T *ptr) const -> void { RefTraits<T>::Free(ptr); }
};

template <typename T>
struct Ref : std::unique_ptr<T, RefDeleter<T>>
{
    using base = std::unique_ptr<T, RefDeleter<T>>;

    /// Owns nothing
    Ref() noexcept = default;

    /// Takes ownership of the pointer
    explicit Ref(T *x) noexcept : base{x} {}

    Ref(Ref &&ref) noexcept = default;
    Ref(const Ref &ref) noexcept {
        *this = ref;
    }

    Ref &operator=(Ref&&) noexcept = default;
    Ref &operator=(const Ref &ref) noexcept {
        if (ref) {
            RefTraits<T>::UpRef(ref.get());
        }
        this->reset(ref.get());
        return *this;
    }
};