Chris@102: // Copyright Kevlin Henney, 2000-2005.
Chris@102: // Copyright Alexander Nasonov, 2006-2010.
Chris@102: // Copyright Antony Polukhin, 2011-2014.
Chris@102: //
Chris@102: // Distributed under the Boost Software License, Version 1.0. (See
Chris@102: // accompanying file LICENSE_1_0.txt or copy at
Chris@102: // http://www.boost.org/LICENSE_1_0.txt)
Chris@102: //
Chris@102: // what:  lexical_cast custom keyword cast
Chris@102: // who:   contributed by Kevlin Henney,
Chris@102: //        enhanced with contributions from Terje Slettebo,
Chris@102: //        with additional fixes and suggestions from Gennaro Prota,
Chris@102: //        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
Chris@102: //        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
Chris@102: //        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
Chris@102: // when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014
Chris@102: 
Chris@102: #ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
Chris@102: #define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
Chris@102: 
Chris@102: #include <boost/config.hpp>
Chris@102: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@102: #   pragma once
Chris@102: #endif
Chris@102: 
Chris@102: #include <boost/limits.hpp>
Chris@102: #include <boost/mpl/if.hpp>
Chris@102: #include <boost/type_traits/ice.hpp>
Chris@102: #include <boost/type_traits/make_unsigned.hpp>
Chris@102: #include <boost/type_traits/is_signed.hpp>
Chris@102: #include <boost/type_traits/is_integral.hpp>
Chris@102: #include <boost/type_traits/is_arithmetic.hpp>
Chris@102: #include <boost/type_traits/is_base_of.hpp>
Chris@102: #include <boost/type_traits/is_float.hpp>
Chris@102: 
Chris@102: #include <boost/numeric/conversion/cast.hpp>
Chris@102: 
Chris@102: namespace boost { namespace detail {
Chris@102: 
Chris@102: template <class Source >
Chris@102: struct detect_precision_loss
Chris@102: {
Chris@102:     typedef Source source_type;
Chris@102:     typedef boost::numeric::Trunc<Source> Rounder;
Chris@102:     typedef BOOST_DEDUCED_TYPENAME mpl::if_<
Chris@102:         boost::is_arithmetic<Source>, Source, Source const&
Chris@102:     >::type argument_type ;
Chris@102: 
Chris@102:     static inline source_type nearbyint(argument_type s, bool& is_ok) BOOST_NOEXCEPT {
Chris@102:         const source_type near_int = Rounder::nearbyint(s);
Chris@102:         if (near_int && is_ok) {
Chris@102:             const source_type orig_div_round = s / near_int;
Chris@102:             const source_type eps = std::numeric_limits<source_type>::epsilon();
Chris@102: 
Chris@102:             is_ok = !((orig_div_round > 1 ? orig_div_round - 1 : 1 - orig_div_round) > eps);
Chris@102:         }
Chris@102: 
Chris@102:         return s;
Chris@102:     }
Chris@102: 
Chris@102:     typedef typename Rounder::round_style round_style;
Chris@102: };
Chris@102: 
Chris@102: template <typename Base, class Source>
Chris@102: struct fake_precision_loss: public Base
Chris@102: {
Chris@102:     typedef Source source_type ;
Chris@102:     typedef BOOST_DEDUCED_TYPENAME mpl::if_<
Chris@102:         boost::is_arithmetic<Source>, Source, Source const&
Chris@102:     >::type argument_type ;
Chris@102: 
Chris@102:     static inline source_type nearbyint(argument_type s, bool& /*is_ok*/) BOOST_NOEXCEPT {
Chris@102:         return s;
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: struct nothrow_overflow_handler
Chris@102: {
Chris@102:     inline bool operator() ( boost::numeric::range_check_result r ) const BOOST_NOEXCEPT {
Chris@102:         return (r == boost::numeric::cInRange);
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: template <typename Target, typename Source>
Chris@102: inline bool noexcept_numeric_convert(const Source& arg, Target& result) BOOST_NOEXCEPT {
Chris@102:     typedef boost::numeric::converter<
Chris@102:             Target,
Chris@102:             Source,
Chris@102:             boost::numeric::conversion_traits<Target, Source >,
Chris@102:             nothrow_overflow_handler,
Chris@102:             detect_precision_loss<Source >
Chris@102:     > converter_orig_t;
Chris@102: 
Chris@102:     typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
Chris@102:         boost::is_base_of< detect_precision_loss<Source >, converter_orig_t >::value,
Chris@102:         converter_orig_t,
Chris@102:         fake_precision_loss<converter_orig_t, Source>
Chris@102:     >::type converter_t;
Chris@102: 
Chris@102:     bool res = nothrow_overflow_handler()(converter_t::out_of_range(arg));
Chris@102:     result = converter_t::low_level_convert(converter_t::nearbyint(arg, res));
Chris@102:     return res;
Chris@102: }
Chris@102: 
Chris@102: template <typename Target, typename Source>
Chris@102: struct lexical_cast_dynamic_num_not_ignoring_minus
Chris@102: {
Chris@102:     static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
Chris@102:         return noexcept_numeric_convert<Target, Source >(arg, result);
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: template <typename Target, typename Source>
Chris@102: struct lexical_cast_dynamic_num_ignoring_minus
Chris@102: {
Chris@102:     static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
Chris@102:         typedef BOOST_DEDUCED_TYPENAME boost::mpl::eval_if_c<
Chris@102:                 boost::is_float<Source>::value,
Chris@102:                 boost::mpl::identity<Source>,
Chris@102:                 boost::make_unsigned<Source>
Chris@102:         >::type usource_t;
Chris@102: 
Chris@102:         if (arg < 0) {
Chris@102:             const bool res = noexcept_numeric_convert<Target, usource_t>(0u - arg, result);
Chris@102:             result = static_cast<Target>(0u - result);
Chris@102:             return res;
Chris@102:         } else {
Chris@102:             return noexcept_numeric_convert<Target, usource_t>(arg, result);
Chris@102:         }
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: /*
Chris@102:  * lexical_cast_dynamic_num follows the rules:
Chris@102:  * 1) If Source can be converted to Target without precision loss and
Chris@102:  * without overflows, then assign Source to Target and return
Chris@102:  *
Chris@102:  * 2) If Source is less than 0 and Target is an unsigned integer,
Chris@102:  * then negate Source, check the requirements of rule 1) and if
Chris@102:  * successful, assign static_casted Source to Target and return
Chris@102:  *
Chris@102:  * 3) Otherwise throw a bad_lexical_cast exception
Chris@102:  *
Chris@102:  *
Chris@102:  * Rule 2) required because boost::lexical_cast has the behavior of
Chris@102:  * stringstream, which uses the rules of scanf for conversions. And
Chris@102:  * in the C99 standard for unsigned input value minus sign is
Chris@102:  * optional, so if a negative number is read, no errors will arise
Chris@102:  * and the result will be the two's complement.
Chris@102:  */
Chris@102: template <typename Target, typename Source>
Chris@102: struct dynamic_num_converter_impl
Chris@102: {
Chris@102:     static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
Chris@102:         typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
Chris@102:             boost::type_traits::ice_and<
Chris@102:                 boost::is_unsigned<Target>::value,
Chris@102:                 boost::type_traits::ice_or<
Chris@102:                     boost::is_signed<Source>::value,
Chris@102:                     boost::is_float<Source>::value
Chris@102:                 >::value,
Chris@102:                 boost::type_traits::ice_not<
Chris@102:                     boost::is_same<Source, bool>::value
Chris@102:                 >::value,
Chris@102:                 boost::type_traits::ice_not<
Chris@102:                     boost::is_same<Target, bool>::value
Chris@102:                 >::value
Chris@102:             >::value,
Chris@102:             lexical_cast_dynamic_num_ignoring_minus<Target, Source>,
Chris@102:             lexical_cast_dynamic_num_not_ignoring_minus<Target, Source>
Chris@102:         >::type caster_type;
Chris@102: 
Chris@102:         return caster_type::try_convert(arg, result);
Chris@102:     }
Chris@102: };
Chris@102: 
Chris@102: }} // namespace boost::detail
Chris@102: 
Chris@102: #endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
Chris@102: