ext-boost/boost/numeric/conversion/detail/converter.hpp
2019-08-24 15:39:04 +02:00

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// (c) Copyright Fernando Luis Cacciola Carballal 2000-2004
// Use, modification, and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// See library home page at http://www.boost.org/libs/numeric/conversion
//
// Contact the author at: fernando_cacciola@hotmail.com
//
#ifndef BOOST_NUMERIC_CONVERSION_DETAIL_CONVERTER_FLC_12NOV2002_HPP
#define BOOST_NUMERIC_CONVERSION_DETAIL_CONVERTER_FLC_12NOV2002_HPP
#include <functional>
#include "boost/numeric/conversion/detail/meta.hpp"
#include "boost/numeric/conversion/detail/conversion_traits.hpp"
#include "boost/numeric/conversion/bounds.hpp"
#include "boost/type_traits/is_same.hpp"
#include "boost/mpl/integral_c.hpp"
namespace boost { namespace numeric { namespace convdetail
{
// Integral Constants representing rounding modes
typedef mpl::integral_c<std::float_round_style, std::round_toward_zero> round2zero_c ;
typedef mpl::integral_c<std::float_round_style, std::round_to_nearest> round2nearest_c ;
typedef mpl::integral_c<std::float_round_style, std::round_toward_infinity> round2inf_c ;
typedef mpl::integral_c<std::float_round_style, std::round_toward_neg_infinity> round2neg_inf_c ;
// Metafunction:
//
// for_round_style<RoundStyle,RoundToZero,RoundToNearest,RoundToInf,RoundToNegInf>::type
//
// {RoundStyle} Integral Constant specifying a round style as declared above.
// {RoundToZero,RoundToNearest,RoundToInf,RoundToNegInf} arbitrary types.
//
// Selects one of the 4 types according to the value of RoundStyle.
//
template<class RoundStyle,class RoundToZero,class RoundToNearest,class RoundToInf,class RoundToNegInf>
struct for_round_style
{
typedef ct_switch4<RoundStyle
, round2zero_c, round2nearest_c, round2inf_c // round2neg_inf_c
, RoundToZero , RoundToNearest , RoundToInf , RoundToNegInf
> selector ;
typedef typename selector::type type ;
} ;
//--------------------------------------------------------------------------
// Range Checking Logic.
//
// The range checking logic is built up by combining 1 or 2 predicates.
// Each predicate is encapsulated in a template class and exposes
// the static member function 'apply'.
//
//--------------------------------------------------------------------------
// Because a particular logic can combine either 1 or two predicates, the following
// tags are used to allow the predicate applier to receive 2 preds, but optimize away
// one of them if it is 'non-applicable'
struct non_applicable { typedef mpl::false_ do_apply ; } ;
struct applicable { typedef mpl::true_ do_apply ; } ;
//--------------------------------------------------------------------------
//
// Range Checking Logic implementations.
//
// The following classes, collectivelly named 'Predicates', are instantiated within
// the corresponding range checkers.
// Their static member function 'apply' is called to perform the actual range checking logic.
//--------------------------------------------------------------------------
// s < Lowest(T) ? cNegOverflow : cInRange
//
template<class Traits>
struct LT_LoT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s < static_cast<S>(bounds<T>::lowest()) ? cNegOverflow : cInRange ;
}
} ;
// s < 0 ? cNegOverflow : cInRange
//
template<class Traits>
struct LT_Zero : applicable
{
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s < static_cast<S>(0) ? cNegOverflow : cInRange ;
}
} ;
// s <= Lowest(T)-1 ? cNegOverflow : cInRange
//
template<class Traits>
struct LE_PrevLoT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s <= static_cast<S>(bounds<T>::lowest()) - static_cast<S>(1.0)
? cNegOverflow : cInRange ;
}
} ;
// s < Lowest(T)-0.5 ? cNegOverflow : cInRange
//
template<class Traits>
struct LT_HalfPrevLoT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s < static_cast<S>(bounds<T>::lowest()) - static_cast<S>(0.5)
? cNegOverflow : cInRange ;
}
} ;
// s > Highest(T) ? cPosOverflow : cInRange
//
template<class Traits>
struct GT_HiT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s > static_cast<S>(bounds<T>::highest())
? cPosOverflow : cInRange ;
}
} ;
// s >= Lowest(T) + 1 ? cPosOverflow : cInRange
//
template<class Traits>
struct GE_SuccHiT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s >= static_cast<S>(bounds<T>::highest()) + static_cast<S>(1.0)
? cPosOverflow : cInRange ;
}
} ;
// s >= Lowest(T) + 0.5 ? cPosgOverflow : cInRange
//
template<class Traits>
struct GT_HalfSuccHiT : applicable
{
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename Traits::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
return s >= static_cast<S>(bounds<T>::highest()) + static_cast<S>(0.5)
? cPosOverflow : cInRange ;
}
} ;
//--------------------------------------------------------------------------
//
// Predicate Combiner.
//
// This helper classes are used to possibly combine the range checking logic
// individually performed by the predicates
//
//--------------------------------------------------------------------------
// Applies both predicates: first 'PredA', and if it equals 'cInRange', 'PredB'
template<class PredA, class PredB>
struct applyBoth
{
typedef typename PredA::argument_type argument_type ;
static range_check_result apply ( argument_type s )
{
range_check_result r = PredA::apply(s) ;
if ( r == cInRange )
r = PredB::apply(s);
return r ;
}
} ;
template<class PredA, class PredB>
struct combine
{
typedef applyBoth<PredA,PredB> Both ;
typedef void NNone ; // 'None' is defined as a macro in (/usr/X11R6/include/X11/X.h)
typedef typename PredA::do_apply do_applyA ;
typedef typename PredB::do_apply do_applyB ;
typedef typename for_both<do_applyA, do_applyB, Both, PredA, PredB, NNone>::type type ;
} ;
//--------------------------------------------------------------------------
// Range Checker classes.
//
// The following classes are VISIBLE base classes of the user-level converter<> class.
// They supply the optimized 'out_of_range()' and 'validate_range()' static member functions
// visible in the user interface.
//
//--------------------------------------------------------------------------
// Dummy range checker.
template<class Traits>
struct dummy_range_checker
{
typedef typename Traits::argument_type argument_type ;
static range_check_result out_of_range ( argument_type ) { return cInRange ; }
static void validate_range ( argument_type ) {}
} ;
// Generic range checker.
//
// All the range checking logic for all possible combinations of source and target
// can be arranged in terms of one or two predicates, which test overflow on both neg/pos 'sides'
// of the ranges.
//
// These predicates are given here as IsNegOverflow and IsPosOverflow.
//
template<class Traits, class IsNegOverflow, class IsPosOverflow, class OverflowHandler>
struct generic_range_checker
{
typedef OverflowHandler overflow_handler ;
typedef typename Traits::argument_type argument_type ;
static range_check_result out_of_range ( argument_type s )
{
typedef typename combine<IsNegOverflow,IsPosOverflow>::type Predicate ;
return Predicate::apply(s);
}
static void validate_range ( argument_type s )
{ OverflowHandler()( out_of_range(s) ) ; }
} ;
//--------------------------------------------------------------------------
//
// Selectors for the optimized Range Checker class.
//
//--------------------------------------------------------------------------
template<class Traits,class OverflowHandler>
struct GetRC_Sig2Sig_or_Unsig2Unsig
{
typedef dummy_range_checker<Traits> Dummy ;
typedef LT_LoT<Traits> Pred1 ;
typedef GT_HiT<Traits> Pred2 ;
typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> Normal ;
typedef typename Traits::subranged subranged ;
typedef typename mpl::if_<subranged,Normal,Dummy>::type type ;
} ;
template<class Traits, class OverflowHandler>
struct GetRC_Sig2Unsig
{
typedef LT_Zero<Traits> Pred1 ;
typedef GT_HiT <Traits> Pred2 ;
typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> ChoiceA ;
typedef generic_range_checker<Traits,Pred1,non_applicable,OverflowHandler> ChoiceB ;
typedef typename Traits::target_type T ;
typedef typename Traits::source_type S ;
typedef typename subranged_Unsig2Sig<S,T>::type oposite_subranged ;
typedef typename mpl::not_<oposite_subranged>::type positively_subranged ;
typedef typename mpl::if_<positively_subranged,ChoiceA,ChoiceB>::type type ;
} ;
template<class Traits, class OverflowHandler>
struct GetRC_Unsig2Sig
{
typedef GT_HiT<Traits> Pred1 ;
typedef generic_range_checker<Traits,non_applicable,Pred1,OverflowHandler> type ;
} ;
template<class Traits,class OverflowHandler>
struct GetRC_Int2Int
{
typedef GetRC_Sig2Sig_or_Unsig2Unsig<Traits,OverflowHandler> Sig2SigQ ;
typedef GetRC_Sig2Unsig <Traits,OverflowHandler> Sig2UnsigQ ;
typedef GetRC_Unsig2Sig <Traits,OverflowHandler> Unsig2SigQ ;
typedef Sig2SigQ Unsig2UnsigQ ;
typedef typename Traits::sign_mixture sign_mixture ;
typedef typename
for_sign_mixture<sign_mixture,Sig2SigQ,Sig2UnsigQ,Unsig2SigQ,Unsig2UnsigQ>::type
selector ;
typedef typename selector::type type ;
} ;
template<class Traits>
struct GetRC_Int2Float
{
typedef dummy_range_checker<Traits> type ;
} ;
template<class Traits, class OverflowHandler, class Float2IntRounder>
struct GetRC_Float2Int
{
typedef LE_PrevLoT <Traits> Pred1 ;
typedef GE_SuccHiT <Traits> Pred2 ;
typedef LT_HalfPrevLoT<Traits> Pred3 ;
typedef GT_HalfSuccHiT<Traits> Pred4 ;
typedef GT_HiT <Traits> Pred5 ;
typedef LT_LoT <Traits> Pred6 ;
typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> ToZero ;
typedef generic_range_checker<Traits,Pred3,Pred4,OverflowHandler> ToNearest ;
typedef generic_range_checker<Traits,Pred1,Pred5,OverflowHandler> ToInf ;
typedef generic_range_checker<Traits,Pred6,Pred2,OverflowHandler> ToNegInf ;
typedef typename Float2IntRounder::round_style round_style ;
typedef typename for_round_style<round_style,ToZero,ToNearest,ToInf,ToNegInf>::type type ;
} ;
template<class Traits, class OverflowHandler>
struct GetRC_Float2Float
{
typedef dummy_range_checker<Traits> Dummy ;
typedef LT_LoT<Traits> Pred1 ;
typedef GT_HiT<Traits> Pred2 ;
typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> Normal ;
typedef typename Traits::subranged subranged ;
typedef typename mpl::if_<subranged,Normal,Dummy>::type type ;
} ;
template<class Traits, class OverflowHandler, class Float2IntRounder>
struct GetRC_BuiltIn2BuiltIn
{
typedef GetRC_Int2Int<Traits,OverflowHandler> Int2IntQ ;
typedef GetRC_Int2Float<Traits> Int2FloatQ ;
typedef GetRC_Float2Int<Traits,OverflowHandler,Float2IntRounder> Float2IntQ ;
typedef GetRC_Float2Float<Traits,OverflowHandler> Float2FloatQ ;
typedef typename Traits::int_float_mixture int_float_mixture ;
typedef typename for_int_float_mixture<int_float_mixture, Int2IntQ, Int2FloatQ, Float2IntQ, Float2FloatQ>::type selector ;
typedef typename selector::type type ;
} ;
template<class Traits, class OverflowHandler, class Float2IntRounder>
struct GetRC
{
typedef GetRC_BuiltIn2BuiltIn<Traits,OverflowHandler,Float2IntRounder> BuiltIn2BuiltInQ ;
typedef dummy_range_checker<Traits> Dummy ;
typedef mpl::identity<Dummy> DummyQ ;
typedef typename Traits::udt_builtin_mixture udt_builtin_mixture ;
typedef typename for_udt_builtin_mixture<udt_builtin_mixture,BuiltIn2BuiltInQ,DummyQ,DummyQ,DummyQ>::type selector ;
typedef typename selector::type type ;
} ;
//--------------------------------------------------------------------------
// Converter classes.
//
// The following classes are VISIBLE base classes of the user-level converter<> class.
// They supply the optimized 'nearbyint()' and 'convert()' static member functions
// visible in the user interface.
//
//--------------------------------------------------------------------------
//
// Trivial Converter : used when (cv-unqualified) T == (cv-unqualified) S
//
template<class Traits>
struct trivial_converter_impl : public dummy_range_checker<Traits>
{
typedef Traits traits ;
typedef typename Traits::source_type source_type ;
typedef typename Traits::argument_type argument_type ;
typedef typename Traits::result_type result_type ;
static result_type low_level_convert ( argument_type s ) { return s ; }
static source_type nearbyint ( argument_type s ) { return s ; }
static result_type convert ( argument_type s ) { return s ; }
} ;
//
// Rounding Converter : used for float to integral conversions.
//
template<class Traits,class RangeChecker,class RawConverter,class Float2IntRounder>
struct rounding_converter : public RangeChecker
,public Float2IntRounder
,public RawConverter
{
typedef RangeChecker RangeCheckerBase ;
typedef Float2IntRounder Float2IntRounderBase ;
typedef RawConverter RawConverterBase ;
typedef Traits traits ;
typedef typename Traits::source_type source_type ;
typedef typename Traits::argument_type argument_type ;
typedef typename Traits::result_type result_type ;
static result_type convert ( argument_type s )
{
RangeCheckerBase::validate_range(s);
source_type s1 = Float2IntRounderBase::nearbyint(s);
return RawConverterBase::low_level_convert(s1);
}
} ;
//
// Non-Rounding Converter : used for all other conversions.
//
template<class Traits,class RangeChecker,class RawConverter>
struct non_rounding_converter : public RangeChecker
,public RawConverter
{
typedef RangeChecker RangeCheckerBase ;
typedef RawConverter RawConverterBase ;
typedef Traits traits ;
typedef typename Traits::source_type source_type ;
typedef typename Traits::argument_type argument_type ;
typedef typename Traits::result_type result_type ;
static source_type nearbyint ( argument_type s ) { return s ; }
static result_type convert ( argument_type s )
{
RangeCheckerBase::validate_range(s);
return RawConverterBase::low_level_convert(s);
}
} ;
//--------------------------------------------------------------------------
//
// Selectors for the optimized Converter class.
//
//--------------------------------------------------------------------------
template<class Traits,class OverflowHandler,class Float2IntRounder,class RawConverter, class UserRangeChecker>
struct get_non_trivial_converter
{
typedef GetRC<Traits,OverflowHandler,Float2IntRounder> InternalRangeCheckerQ ;
typedef is_same<UserRangeChecker,UseInternalRangeChecker> use_internal_RC ;
typedef mpl::identity<UserRangeChecker> UserRangeCheckerQ ;
typedef typename
mpl::eval_if<use_internal_RC,InternalRangeCheckerQ,UserRangeCheckerQ>::type
RangeChecker ;
typedef non_rounding_converter<Traits,RangeChecker,RawConverter> NonRounding ;
typedef rounding_converter<Traits,RangeChecker,RawConverter,Float2IntRounder> Rounding ;
typedef mpl::identity<NonRounding> NonRoundingQ ;
typedef mpl::identity<Rounding> RoundingQ ;
typedef typename Traits::int_float_mixture int_float_mixture ;
typedef typename
for_int_float_mixture<int_float_mixture, NonRoundingQ, NonRoundingQ, RoundingQ, NonRoundingQ>::type
selector ;
typedef typename selector::type type ;
} ;
template< class Traits
,class OverflowHandler
,class Float2IntRounder
,class RawConverter
,class UserRangeChecker
>
struct get_converter_impl
{
#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT( 0x0561 ) )
// bcc55 prefers sometimes template parameters to be explicit local types.
// (notice that is is illegal to reuse the names like this)
typedef Traits Traits ;
typedef OverflowHandler OverflowHandler ;
typedef Float2IntRounder Float2IntRounder ;
typedef RawConverter RawConverter ;
typedef UserRangeChecker UserRangeChecker ;
#endif
typedef trivial_converter_impl<Traits> Trivial ;
typedef mpl::identity <Trivial> TrivialQ ;
typedef get_non_trivial_converter< Traits
,OverflowHandler
,Float2IntRounder
,RawConverter
,UserRangeChecker
> NonTrivialQ ;
typedef typename Traits::trivial trivial ;
typedef typename mpl::eval_if<trivial,TrivialQ,NonTrivialQ>::type type ;
} ;
} } } // namespace boost::numeric::convdetail
#endif