libreoffice/basebmp/inc/metafunctions.hxx

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * 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/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you under the Apache
 *   License, Version 2.0 (the "License"); you may not use this file
 *   except in compliance with the License. You may obtain a copy of
 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 */

#ifndef INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX
#define INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX

#include <boost/mpl/integral_c.hpp>
#include <vigra/metaprogramming.hxx>
#include <vigra/numerictraits.hxx>

#include <functional>
#include <limits>
#include <type_traits>

namespace basebmp
{

// TODO(Q3): move to generic place (o3tl?)

/** template meta function: add const qualifier to 2nd type, if given
    1st type has it
*/
template<typename A, typename B> struct clone_const
{
    typedef B type;
};
template<typename A, typename B> struct clone_const<const A,B>
{
    typedef const B type;
};

/** template meta function: add const qualifier to plain type (if not
    already there)
 */
template <typename T> struct add_const
{
    typedef const T type;
};
template <typename T> struct add_const<const T>
{
    typedef const T type;
};

/// template meta function: remove const qualifier from plain type
template <typename T> struct remove_const
{
    typedef T type;
};
template <typename T> struct remove_const<const T>
{
    typedef T type;
};



/// Base class for an adaptable ternary functor
template< typename A1, typename A2, typename A3, typename R > struct TernaryFunctorBase
{
    typedef A1 first_argument_type;
    typedef A2 second_argument_type;
    typedef A3 third_argument_type;
    typedef R  result_type;
};



/** template meta function: ensure that given integer type is unsigned

    If given integer type is already unsigned, return as-is -
    otherwise, convert to unsigned type of same or greater range.
 */
template< typename T > struct make_unsigned;

#define BASEBMP_MAKE_UNSIGNED(T,U)        \
    template<> struct make_unsigned<T> { \
        typedef U type; \
    };

BASEBMP_MAKE_UNSIGNED(signed char,unsigned char)
BASEBMP_MAKE_UNSIGNED(unsigned char,unsigned char)
BASEBMP_MAKE_UNSIGNED(short,unsigned short)
BASEBMP_MAKE_UNSIGNED(unsigned short,unsigned short)
BASEBMP_MAKE_UNSIGNED(int,unsigned int)
BASEBMP_MAKE_UNSIGNED(unsigned int,unsigned int)
BASEBMP_MAKE_UNSIGNED(long,unsigned long)
BASEBMP_MAKE_UNSIGNED(unsigned long,unsigned long)

#undef BASEBMP_MAKE_UNSIGNED

/// cast integer to unsigned type of similar size
template< typename T > inline typename make_unsigned<T>::type unsigned_cast( T value )
{
    return static_cast< typename make_unsigned<T>::type >(value);
}



/// returns true, if given number is strictly less than 0
template< typename T > inline bool is_negative( T x )
{
    return x < 0;
}

/// Overload for ints (branch-free)
inline bool is_negative( int x )
{
    // force logic shift (result for signed shift right is undefined)
    return static_cast<unsigned int>(x) >> (sizeof(int)*8-1);
}



/// Results in VigraTrueType, if T is of integer type and scalar
template< typename T, typename trueCase, typename falseCase >
struct ifScalarIntegral
{
    typedef
    typename vigra::If<
        typename vigra::NumericTraits< T >::isIntegral,
        typename vigra::If<
            typename vigra::NumericTraits< T >::isScalar,
            trueCase,
            falseCase >::type,
        falseCase >::type type;
};

/// Results in VigraTrueType, if T is of non-integer type and scalar
template< typename T, typename trueCase, typename falseCase >
struct ifScalarNonIntegral
{
    typedef
    typename vigra::If<
        typename vigra::NumericTraits< T >::isIntegral,
        falseCase,
        typename vigra::If<
            typename vigra::NumericTraits< T >::isScalar,
            trueCase,
            falseCase >::type >::type type;
};

/// Results in VigraTrueType, if both T1 and T2 are of integer type and scalar
template< typename T1, typename T2, typename trueCase, typename falseCase >
struct ifBothScalarIntegral
{
    typedef
    typename ifScalarIntegral<
        T1,
        typename ifScalarIntegral<
            T2,
            trueCase,
            falseCase >::type,
        falseCase >::type type;
};



/// Count number of trailing zeros
template< unsigned int val > struct numberOfTrailingZeros
{
    enum { next = val >> 1 };
    enum { value = vigra::IfBool< (val & 1) == 0,
                                  numberOfTrailingZeros<next>,
                                  boost::mpl::integral_c< int,-1 > > ::type::value + 1 };
};

template<> struct numberOfTrailingZeros<0>
{
    enum { value = 0 };
};



/// Count number of one bits
template< unsigned int val > struct bitcount
{
    enum { next = val >> 1 };
    enum { value = bitcount<next>::value + (val & 1) };
};

template<> struct bitcount<0>
{
    enum { value = 0 };
};



/// Shift left for positive shift value, and right otherwise
template< typename T > inline T shiftLeft( T v, int shift )
{
    return shift > 0 ? v << shift : v >> (-shift);
}

/// Shift right for positive shift value, and left otherwise
template< typename T > inline T shiftRight( T v, int shift )
{
    // Avoid undefined behavior and only shift by less than the length in bits
    // of the promoted left operand:
    static_assert(
        std::is_unsigned<T>::value,
        "must be unsigned for promotedBits and the below ': 0' to be correct");
    using Promoted = decltype(+T());
    auto const promotedBits = std::numeric_limits<Promoted>::digits;
    return shift >= 0
        ? shift < promotedBits ? Promoted(v) >> shift : 0
        : -shift < promotedBits ? Promoted(v) << (-shift) : 0;
}

} // namespace basebmp

#endif /* INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX */

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