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1 | // Copyright Kevlin Henney, 2000-2005. |
2 | // Copyright Alexander Nasonov, 2006-2010. | |
3 | // Copyright Antony Polukhin, 2011-2014. | |
4 | // | |
5 | // Distributed under the Boost Software License, Version 1.0. (See | |
6 | // accompanying file LICENSE_1_0.txt or copy at | |
7 | // http://www.boost.org/LICENSE_1_0.txt) | |
8 | // | |
9 | // what: lexical_cast custom keyword cast | |
10 | // who: contributed by Kevlin Henney, | |
11 | // enhanced with contributions from Terje Slettebo, | |
12 | // with additional fixes and suggestions from Gennaro Prota, | |
13 | // Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov, | |
14 | // Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann, | |
15 | // Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters | |
16 | // when: November 2000, March 2003, June 2005, June 2006, March 2011 - 2014 | |
17 | ||
18 | #ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP | |
19 | #define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP | |
20 | ||
21 | #include <boost/config.hpp> | |
22 | #ifdef BOOST_HAS_PRAGMA_ONCE | |
23 | # pragma once | |
24 | #endif | |
25 | ||
26 | #include <boost/limits.hpp> | |
27 | #include <boost/mpl/eval_if.hpp> | |
28 | #include <boost/mpl/identity.hpp> | |
29 | #include <boost/mpl/if.hpp> | |
30 | #include <boost/type_traits/make_unsigned.hpp> | |
31 | #include <boost/type_traits/is_signed.hpp> | |
32 | #include <boost/type_traits/is_integral.hpp> | |
33 | #include <boost/type_traits/is_arithmetic.hpp> | |
34 | #include <boost/type_traits/is_base_of.hpp> | |
35 | #include <boost/type_traits/is_float.hpp> | |
36 | ||
37 | #include <boost/numeric/conversion/cast.hpp> | |
38 | ||
39 | namespace boost { namespace detail { | |
40 | ||
41 | template <class Source > | |
42 | struct detect_precision_loss | |
43 | { | |
44 | typedef Source source_type; | |
45 | typedef boost::numeric::Trunc<Source> Rounder; | |
46 | typedef BOOST_DEDUCED_TYPENAME mpl::if_< | |
47 | boost::is_arithmetic<Source>, Source, Source const& | |
48 | >::type argument_type ; | |
49 | ||
50 | static inline source_type nearbyint(argument_type s, bool& is_ok) BOOST_NOEXCEPT { | |
51 | const source_type near_int = Rounder::nearbyint(s); | |
52 | if (near_int && is_ok) { | |
53 | const source_type orig_div_round = s / near_int; | |
54 | const source_type eps = std::numeric_limits<source_type>::epsilon(); | |
55 | ||
56 | is_ok = !((orig_div_round > 1 ? orig_div_round - 1 : 1 - orig_div_round) > eps); | |
57 | } | |
58 | ||
59 | return s; | |
60 | } | |
61 | ||
62 | typedef typename Rounder::round_style round_style; | |
63 | }; | |
64 | ||
65 | template <typename Base, class Source> | |
66 | struct fake_precision_loss: public Base | |
67 | { | |
68 | typedef Source source_type ; | |
69 | typedef BOOST_DEDUCED_TYPENAME mpl::if_< | |
70 | boost::is_arithmetic<Source>, Source, Source const& | |
71 | >::type argument_type ; | |
72 | ||
73 | static inline source_type nearbyint(argument_type s, bool& /*is_ok*/) BOOST_NOEXCEPT { | |
74 | return s; | |
75 | } | |
76 | }; | |
77 | ||
78 | struct nothrow_overflow_handler | |
79 | { | |
80 | inline bool operator() ( boost::numeric::range_check_result r ) const BOOST_NOEXCEPT { | |
81 | return (r == boost::numeric::cInRange); | |
82 | } | |
83 | }; | |
84 | ||
85 | template <typename Target, typename Source> | |
86 | inline bool noexcept_numeric_convert(const Source& arg, Target& result) BOOST_NOEXCEPT { | |
87 | typedef boost::numeric::converter< | |
88 | Target, | |
89 | Source, | |
90 | boost::numeric::conversion_traits<Target, Source >, | |
91 | nothrow_overflow_handler, | |
92 | detect_precision_loss<Source > | |
93 | > converter_orig_t; | |
94 | ||
95 | typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c< | |
96 | boost::is_base_of< detect_precision_loss<Source >, converter_orig_t >::value, | |
97 | converter_orig_t, | |
98 | fake_precision_loss<converter_orig_t, Source> | |
99 | >::type converter_t; | |
100 | ||
101 | bool res = nothrow_overflow_handler()(converter_t::out_of_range(arg)); | |
102 | result = converter_t::low_level_convert(converter_t::nearbyint(arg, res)); | |
103 | return res; | |
104 | } | |
105 | ||
106 | template <typename Target, typename Source> | |
107 | struct lexical_cast_dynamic_num_not_ignoring_minus | |
108 | { | |
109 | static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT { | |
110 | return noexcept_numeric_convert<Target, Source >(arg, result); | |
111 | } | |
112 | }; | |
113 | ||
114 | template <typename Target, typename Source> | |
115 | struct lexical_cast_dynamic_num_ignoring_minus | |
116 | { | |
117 | static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT { | |
118 | typedef BOOST_DEDUCED_TYPENAME boost::mpl::eval_if_c< | |
119 | boost::is_float<Source>::value, | |
120 | boost::mpl::identity<Source>, | |
121 | boost::make_unsigned<Source> | |
122 | >::type usource_t; | |
123 | ||
124 | if (arg < 0) { | |
125 | const bool res = noexcept_numeric_convert<Target, usource_t>(0u - arg, result); | |
126 | result = static_cast<Target>(0u - result); | |
127 | return res; | |
128 | } else { | |
129 | return noexcept_numeric_convert<Target, usource_t>(arg, result); | |
130 | } | |
131 | } | |
132 | }; | |
133 | ||
134 | /* | |
135 | * lexical_cast_dynamic_num follows the rules: | |
136 | * 1) If Source can be converted to Target without precision loss and | |
137 | * without overflows, then assign Source to Target and return | |
138 | * | |
139 | * 2) If Source is less than 0 and Target is an unsigned integer, | |
140 | * then negate Source, check the requirements of rule 1) and if | |
141 | * successful, assign static_casted Source to Target and return | |
142 | * | |
143 | * 3) Otherwise throw a bad_lexical_cast exception | |
144 | * | |
145 | * | |
146 | * Rule 2) required because boost::lexical_cast has the behavior of | |
147 | * stringstream, which uses the rules of scanf for conversions. And | |
148 | * in the C99 standard for unsigned input value minus sign is | |
149 | * optional, so if a negative number is read, no errors will arise | |
150 | * and the result will be the two's complement. | |
151 | */ | |
152 | template <typename Target, typename Source> | |
153 | struct dynamic_num_converter_impl | |
154 | { | |
155 | static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT { | |
156 | typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c< | |
157 | boost::is_unsigned<Target>::value && | |
158 | (boost::is_signed<Source>::value || boost::is_float<Source>::value) && | |
159 | !(boost::is_same<Source, bool>::value) && | |
160 | !(boost::is_same<Target, bool>::value), | |
161 | lexical_cast_dynamic_num_ignoring_minus<Target, Source>, | |
162 | lexical_cast_dynamic_num_not_ignoring_minus<Target, Source> | |
163 | >::type caster_type; | |
164 | ||
165 | #if 0 | |
166 | ||
167 | typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_< | |
168 | BOOST_DEDUCED_TYPENAME boost::mpl::and_< | |
169 | boost::is_unsigned<Target>, | |
170 | boost::mpl::or_< | |
171 | boost::is_signed<Source>, | |
172 | boost::is_float<Source> | |
173 | >, | |
174 | boost::mpl::not_< | |
175 | boost::is_same<Source, bool> | |
176 | >, | |
177 | boost::mpl::not_< | |
178 | boost::is_same<Target, bool> | |
179 | > | |
180 | >::type, | |
181 | lexical_cast_dynamic_num_ignoring_minus<Target, Source>, | |
182 | lexical_cast_dynamic_num_not_ignoring_minus<Target, Source> | |
183 | >::type caster_type; | |
184 | ||
185 | #endif | |
186 | ||
187 | return caster_type::try_convert(arg, result); | |
188 | } | |
189 | }; | |
190 | ||
191 | }} // namespace boost::detail | |
192 | ||
193 | #endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP | |
194 |