libcruft-util/typeidx.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2017 Danny Robson <danny@nerdcruft.net>
 */

#ifndef CRUFT_UTIL_TYPEIDX_HPP
#define CRUFT_UTIL_TYPEIDX_HPP

#include <cstdint>

namespace util {
    namespace detail { int typeidx_next (void); }

    /// return a globally unique runtime ID for a given type.
    ///
    /// this is intended to be used as a lightweight type check for variants
    /// and such without requiring RTTI.
    ///
    /// the identifier is constructed at runtime and is not guaranteed to be
    /// stable across executions (particularly in the case of threads and
    /// other non-determinism). however it _is_ threadsafe to call this.
    ///
    /// the range of identifiers is _probably_ contiguous starting from zero.
    /// this should not be relied upon for correctness, but may be used for
    /// performance concerns.
    template <typename T>
    int
    typeidx (void)
    {
        static auto id = detail::typeidx_next ();
        return id;
    }
}

#endif