source: vbox/trunk/include/iprt/cpp/meta.h

/** @file
 * IPRT - C++ Meta programming.
 */

/*
 * Copyright (C) 2011-2023 Oracle and/or its affiliates.
 *
 * This file is part of VirtualBox base platform packages, as
 * available from https://www.virtualbox.org.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, in version 3 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses>.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
 * in the VirtualBox distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
 */

#ifndef IPRT_INCLUDED_cpp_meta_h
#define IPRT_INCLUDED_cpp_meta_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif

#include <iprt/types.h>

/** @defgroup grp_rt_cpp_meta   C++ Meta programming utilities
 * @ingroup grp_rt_cpp
 * @{
 */

/**
 * Check for a condition on compile time and dependent of the result TrueResult
 * or FalseResult will be defined.
 *
 * @param   Condition     Condition to check.
 * @param   TrueResult    Result when condition is true.
 * @param   FalseResult   Result when condition is false
 */
template <bool Condition, typename TrueResult, typename FalseResult>
struct RTCIf;

/**
 * Check for a condition on compile time and dependent of the result TrueResult
 * or FalseResult will be defined.
 *
 * True specialization of RTCIf.
 *
 * @param   TrueResult    Result when condition is true.
 * @param   FalseResult   Result when condition is false
 */
template <typename TrueResult, typename FalseResult>
struct RTCIf<true, TrueResult, FalseResult>
{
    typedef TrueResult result;
};

/**
 * Check for a condition on compile time and dependent of the result TrueResult
 * or FalseResult will be defined.
 *
 * False specialization of RTCIf.
 *
 * @param   TrueResult    Result when condition is true.
 * @param   FalseResult   Result when condition is false
 */
template <typename TrueResult, typename FalseResult>
struct RTCIf<false, TrueResult, FalseResult>
{
    typedef FalseResult result;
};

/**
 * Check if @a T is a pointer or not at compile time and dependent of the
 * result TrueResult or FalseResult will be defined.
 *
 * False version of RTCIfPtr.
 *
 * @param   Condition     Condition to check.
 * @param   TrueResult    Result when condition is true.
 * @param   FalseResult   Result when condition is false
 */
template <class T, typename TrueResult, typename FalseResult>
struct RTCIfPtr
{
    typedef FalseResult result;
};

/**
 * Check if @a T is a pointer or not at compile time and dependent of the
 * result TrueResult or FalseResult will be defined.
 *
 * True specialization of RTCIfPtr.
 *
 * @param   Condition     Condition to check.
 * @param   TrueResult    Result when condition is true.
 * @param   FalseResult   Result when condition is false
 */
template <class T, typename TrueResult, typename FalseResult>
struct RTCIfPtr<T*, TrueResult, FalseResult>
{
    typedef TrueResult result;
};

/** @} */

#endif /* !IPRT_INCLUDED_cpp_meta_h */