8bde421cce
...claiming that "right shifting v by more than 15 bits always yields zero," apparently diagnosing an instanatiation of the template for T = unsigned short. Change-Id: I7c210ff17e4aef8f0e703cc30518f3420e67e7c1
228 lines
6.2 KiB
C++
228 lines
6.2 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* This file incorporates work covered by the following license notice:
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright
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* ownership. The ASF licenses this file to you under the Apache
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* License, Version 2.0 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.apache.org/licenses/LICENSE-2.0 .
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*/
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#ifndef INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX
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#define INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX
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#include <boost/mpl/integral_c.hpp>
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#include <vigra/metaprogramming.hxx>
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#include <vigra/numerictraits.hxx>
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#include <functional>
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#include <limits>
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#include <type_traits>
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namespace basebmp
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{
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// TODO(Q3): move to generic place (o3tl?)
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/** template meta function: add const qualifier to 2nd type, if given
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1st type has it
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*/
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template<typename A, typename B> struct clone_const
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{
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typedef B type;
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};
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template<typename A, typename B> struct clone_const<const A,B>
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{
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typedef const B type;
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};
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/** template meta function: add const qualifier to plain type (if not
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already there)
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*/
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template <typename T> struct add_const
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{
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typedef const T type;
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};
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template <typename T> struct add_const<const T>
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{
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typedef const T type;
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};
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/// template meta function: remove const qualifier from plain type
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template <typename T> struct remove_const
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{
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typedef T type;
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};
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template <typename T> struct remove_const<const T>
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{
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typedef T type;
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};
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/// Base class for an adaptable ternary functor
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template< typename A1, typename A2, typename A3, typename R > struct TernaryFunctorBase
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{
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typedef A1 first_argument_type;
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typedef A2 second_argument_type;
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typedef A3 third_argument_type;
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typedef R result_type;
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};
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/** template meta function: ensure that given integer type is unsigned
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If given integer type is already unsigned, return as-is -
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otherwise, convert to unsigned type of same or greater range.
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*/
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template< typename T > struct make_unsigned;
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#define BASEBMP_MAKE_UNSIGNED(T,U) \
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template<> struct make_unsigned<T> { \
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typedef U type; \
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};
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BASEBMP_MAKE_UNSIGNED(signed char,unsigned char)
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BASEBMP_MAKE_UNSIGNED(unsigned char,unsigned char)
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BASEBMP_MAKE_UNSIGNED(short,unsigned short)
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BASEBMP_MAKE_UNSIGNED(unsigned short,unsigned short)
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BASEBMP_MAKE_UNSIGNED(int,unsigned int)
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BASEBMP_MAKE_UNSIGNED(unsigned int,unsigned int)
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BASEBMP_MAKE_UNSIGNED(long,unsigned long)
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BASEBMP_MAKE_UNSIGNED(unsigned long,unsigned long)
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#undef BASEBMP_MAKE_UNSIGNED
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/// cast integer to unsigned type of similar size
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template< typename T > inline typename make_unsigned<T>::type unsigned_cast( T value )
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{
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return static_cast< typename make_unsigned<T>::type >(value);
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}
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/// returns true, if given number is strictly less than 0
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template< typename T > inline bool is_negative( T x )
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{
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return x < 0;
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}
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/// Overload for ints (branch-free)
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inline bool is_negative( int x )
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{
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// force logic shift (result for signed shift right is undefined)
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return static_cast<unsigned int>(x) >> (sizeof(int)*8-1);
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}
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/// Results in VigraTrueType, if T is of integer type and scalar
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template< typename T, typename trueCase, typename falseCase >
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struct ifScalarIntegral
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{
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typedef
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typename vigra::If<
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typename vigra::NumericTraits< T >::isIntegral,
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typename vigra::If<
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typename vigra::NumericTraits< T >::isScalar,
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trueCase,
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falseCase >::type,
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falseCase >::type type;
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};
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/// Results in VigraTrueType, if T is of non-integer type and scalar
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template< typename T, typename trueCase, typename falseCase >
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struct ifScalarNonIntegral
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{
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typedef
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typename vigra::If<
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typename vigra::NumericTraits< T >::isIntegral,
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falseCase,
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typename vigra::If<
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typename vigra::NumericTraits< T >::isScalar,
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trueCase,
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falseCase >::type >::type type;
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};
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/// Results in VigraTrueType, if both T1 and T2 are of integer type and scalar
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template< typename T1, typename T2, typename trueCase, typename falseCase >
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struct ifBothScalarIntegral
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{
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typedef
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typename ifScalarIntegral<
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T1,
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typename ifScalarIntegral<
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T2,
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trueCase,
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falseCase >::type,
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falseCase >::type type;
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};
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/// Count number of trailing zeros
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template< unsigned int val > struct numberOfTrailingZeros
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{
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enum { next = val >> 1 };
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enum { value = vigra::IfBool< (val & 1) == 0,
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numberOfTrailingZeros<next>,
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boost::mpl::integral_c< int,-1 > > ::type::value + 1 };
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};
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template<> struct numberOfTrailingZeros<0>
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{
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enum { value = 0 };
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};
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/// Count number of one bits
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template< unsigned int val > struct bitcount
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{
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enum { next = val >> 1 };
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enum { value = bitcount<next>::value + (val & 1) };
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};
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template<> struct bitcount<0>
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{
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enum { value = 0 };
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};
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/// Shift left for positive shift value, and right otherwise
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template< typename T > inline T shiftLeft( T v, int shift )
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{
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return shift > 0 ? v << shift : v >> (-shift);
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}
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/// Shift right for positive shift value, and left otherwise
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template< typename T > inline T shiftRight( T v, int shift )
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{
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// Avoid undefined behavior and only shift by less than the length in bits
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// of the promoted left operand:
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static_assert(
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std::is_unsigned<T>::value,
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"must be unsigned for promotedBits and the below ': 0' to be correct");
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using Promoted = decltype(+T());
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auto const promotedBits = std::numeric_limits<Promoted>::digits;
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return shift >= 0
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? shift < promotedBits ? Promoted(v) >> shift : 0
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: -shift < promotedBits ? Promoted(v) << (-shift) : 0;
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}
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} // namespace basebmp
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#endif /* INCLUDED_BASEBMP_INC_METAFUNCTIONS_HXX */
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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