1#ifndef CONSTRAINED_VALUE_HPP___
2#define CONSTRAINED_VALUE_HPP___
3
4/* Copyright (c) 2002,2003 CrystalClear Software, Inc.
5 * Use, modification and distribution is subject to the
6 * Boost Software License, Version 1.0. (See accompanying
7 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
8 * Author: Jeff Garland
9 * $Date$
10 */
11
12#include <exception>
13#include <stdexcept>
14#include <boost/config.hpp>
15#include <boost/throw_exception.hpp>
16#include <boost/type_traits/conditional.hpp>
17#include <boost/type_traits/is_base_of.hpp>
18
19namespace boost {
20
21//! Namespace containing constrained_value template and types
22namespace CV {
23 //! Represent a min or max violation type
24 enum violation_enum {min_violation, max_violation};
25
26 //! A template to specify a constrained basic value type
27 /*! This template provides a quick way to generate
28 * an integer type with a constrained range. The type
29 * provides for the ability to specify the min, max, and
30 * and error handling policy.
31 *
32 * <b>value policies</b>
33 * A class that provides the range limits via the min and
34 * max functions as well as a function on_error that
35 * determines how errors are handled. A common strategy
36 * would be to assert or throw and exception. The on_error
37 * is passed both the current value and the new value that
38 * is in error.
39 *
40 */
41 template<class value_policies>
42 class BOOST_SYMBOL_VISIBLE constrained_value {
43 public:
44 typedef typename value_policies::value_type value_type;
45 // typedef except_type exception_type;
46 BOOST_CXX14_CONSTEXPR constrained_value(value_type value) : value_((min)())
47 {
48 assign(value);
49 }
50 BOOST_CXX14_CONSTEXPR constrained_value& operator=(value_type v)
51 {
52 assign(value: v);
53 return *this;
54 }
55 //! Return the max allowed value (traits method)
56 static BOOST_CONSTEXPR value_type
57 max BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::max)();}
58
59 //! Return the min allowed value (traits method)
60 static BOOST_CONSTEXPR value_type
61 min BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::min)();}
62
63 //! Coerce into the representation type
64 BOOST_CXX14_CONSTEXPR operator value_type() const {return value_;}
65 protected:
66 value_type value_;
67 private:
68 BOOST_CXX14_CONSTEXPR void assign(value_type value)
69 {
70 //adding 1 below gets rid of a compiler warning which occurs when the
71 //min_value is 0 and the type is unsigned....
72 if (value+1 < (min)()+1) {
73 value_policies::on_error(value_, value, min_violation);
74 return;
75 }
76 if (value > (max)()) {
77 value_policies::on_error(value_, value, max_violation);
78 return;
79 }
80 value_ = value;
81 }
82};
83
84 //! Template to shortcut the constrained_value policy creation process
85 template<typename rep_type, rep_type min_value,
86 rep_type max_value, class exception_type>
87 class BOOST_SYMBOL_VISIBLE simple_exception_policy
88 {
89 struct BOOST_SYMBOL_VISIBLE exception_wrapper : public exception_type
90 {
91 // In order to support throw_exception mechanism in the BOOST_NO_EXCEPTIONS mode,
92 // we'll have to provide a way to acquire std::exception from the exception being thrown.
93 // However, we cannot derive from it, since it would make it interceptable by this class,
94 // which might not be what the user wanted.
95 operator std::out_of_range () const
96 {
97 // TODO: Make the message more descriptive by using arguments to on_error
98 return std::out_of_range("constrained value boundary has been violated");
99 }
100 };
101
102 typedef typename conditional<
103 is_base_of< std::exception, exception_type >::value,
104 exception_type,
105 exception_wrapper
106 >::type actual_exception_type;
107
108 public:
109 typedef rep_type value_type;
110 static BOOST_CONSTEXPR rep_type
111 min BOOST_PREVENT_MACRO_SUBSTITUTION () { return min_value; }
112
113 static BOOST_CONSTEXPR rep_type
114 max BOOST_PREVENT_MACRO_SUBSTITUTION () { return max_value; }
115
116 static void on_error(rep_type, rep_type, violation_enum)
117 {
118 boost::throw_exception(actual_exception_type());
119 }
120 };
121
122
123
124} } //namespace CV
125
126
127
128
129#endif
130

source code of include/boost/date_time/constrained_value.hpp