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