libcruft-util/pointer.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 2011-2017 Danny Robson <danny@nerdcruft.net>
 */

#ifndef CRUFT_UTIL_POINTER_HPP
#define CRUFT_UTIL_POINTER_HPP

#include "view.hpp"

#include <cstddef>
#include <cstdint>


namespace util {
    ///////////////////////////////////////////////////////////////////////////
    /// round the pointer upwards to satisfy the provided alignment
    template <typename T>
    constexpr T*
    align (T *_ptr, size_t alignment)
    {
        // we perform this as two steps to avoid unnecessarily incrementing when
        // remainder is zero.
        auto ptr = reinterpret_cast<uintptr_t> (_ptr);
        if (ptr % alignment)
            ptr += alignment - ptr % alignment;
        return reinterpret_cast<T*> (ptr);
    }


    ///////////////////////////////////////////////////////////////////////////
    template <typename ValueT>
    constexpr util::view<ValueT*>
    align (util::view<ValueT*> value, size_t alignment)
    {
        return {
            align (value.begin (), alignment),
            value.end ()
        };
    }


    ///------------------------------------------------------------------------
    /// round the pointer upwards to satisfy the provided alignment
    constexpr inline uintptr_t
    align (uintptr_t ptr, size_t alignment)
    {
        // we perform this as two steps to avoid unnecessarily incrementing when
        // remainder is zero.
        if (ptr % alignment)
            ptr += alignment - ptr % alignment;
        return ptr;
    }


    ///------------------------------------------------------------------------
    /// round the pointer upwards to the nearest valid alignment for T
    template <typename T>
    constexpr auto
    align (T *t)
    {
        return align (t, alignof (T));
    }


    ///------------------------------------------------------------------------
    /// round the pointer upwards to the nearest valid alignment for T
    template <typename T>
    constexpr auto
    align (uintptr_t ptr)
    {
        return align (ptr, alignof (T));
    }
}

#endif