libcruft-util/cruft/util/debug/validate.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 2010-2019 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "./assert.hpp"

///////////////////////////////////////////////////////////////////////////////
namespace cruft::debug {
    ///////////////////////////////////////////////////////////////////////////
    // returns true if an instance of type `T' appears to be in a valid state.
    //
    // written as a struct rather than a function so that behaviour may be
    // partially specialised. all users are free to specialise this struct
    // with an user types.
    //
    // all specialisations must be safe to call on arbitrary data without
    // exceptions or faults as this mechanism is used to control some
    // debugging paths which themselves are the configuration points for
    // throwing/logging/etc behaviour.
    //
    // ArgsT is an optional set of auxiliary values that are required to
    // validate the target value.
    template <typename T, typename ...ArgsT>
    struct validator {
        static bool is_valid (T const&, ArgsT const&...) noexcept;
    };


    //-------------------------------------------------------------------------
    template <typename T, typename ...ArgsT>
    bool is_valid (const T &t, const ArgsT &...args) noexcept
    {
        return validator<T,ArgsT...>::is_valid (t, args...);
    }


    //-------------------------------------------------------------------------
    // forwarding validator from a pointer type to a reference type.
    //
    // null pointers are assumed to be invalid
    template <typename T, typename ...ArgsT>
    struct validator<T*,ArgsT...> {
        static bool is_valid (const T *val, ArgsT const &...args) noexcept
        {
            return val && ::cruft::debug::is_valid (*val, args...);
        }
    };


    ///////////////////////////////////////////////////////////////////////////
    // asserts that an instance of type `T' is in a valid state.
    //
    // behaviour will be controlled by NDEBUG and other assertion machinery and
    // so may be optimised out entirely in optimised builds.
    template <typename T>
    void sanity (const T &t)
    {
        (void)t;
        CHECK (is_valid (t));
    }


    //-------------------------------------------------------------------------
    template <
        template<typename...> class T,
        typename ...Args
    >
    void sanity (const T<Args...> &t)
    {
        (void)t;
        CHECK (is_valid (t));
    }


    template <typename ValueT>
    class scoped_sanity {
    public:
        scoped_sanity (ValueT &_value):
            m_value (_value)
        {
            sanity (m_value);
        }

        ~scoped_sanity ()
        {
            sanity (m_value);
        }

    private:
        const ValueT& m_value;
    };
};