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/mpl/if.hpp> |
17 | #include <boost/type_traits/is_base_of.hpp> |
18 | |
19 | namespace boost { |
20 | |
21 | //! Namespace containing constrained_value template and types |
22 | namespace 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 constrained_value { |
43 | public: |
44 | typedef typename value_policies::value_type value_type; |
45 | // typedef except_type exception_type; |
46 | constrained_value(value_type value) : value_((min)()) |
47 | { |
48 | assign(value); |
49 | } |
50 | 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 value_type max BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::max)();} |
57 | //! Return the min allowed value (traits method) |
58 | static value_type min BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::min)();} |
59 | //! Coerce into the representation type |
60 | operator value_type() const {return value_;} |
61 | protected: |
62 | value_type value_; |
63 | private: |
64 | void assign(value_type value) |
65 | { |
66 | //adding 1 below gets rid of a compiler warning which occurs when the |
67 | //min_value is 0 and the type is unsigned.... |
68 | if (value+1 < (min)()+1) { |
69 | value_policies::on_error(value_, value, min_violation); |
70 | return; |
71 | } |
72 | if (value > (max)()) { |
73 | value_policies::on_error(value_, value, max_violation); |
74 | return; |
75 | } |
76 | value_ = value; |
77 | } |
78 | }; |
79 | |
80 | //! Template to shortcut the constrained_value policy creation process |
81 | template<typename rep_type, rep_type min_value, |
82 | rep_type max_value, class exception_type> |
83 | class simple_exception_policy |
84 | { |
85 | struct exception_wrapper : public exception_type |
86 | { |
87 | // In order to support throw_exception mechanism in the BOOST_NO_EXCEPTIONS mode, |
88 | // we'll have to provide a way to acquire std::exception from the exception being thrown. |
89 | // However, we cannot derive from it, since it would make it interceptable by this class, |
90 | // which might not be what the user wanted. |
91 | operator std::out_of_range () const |
92 | { |
93 | // TODO: Make the message more descriptive by using arguments to on_error |
94 | return std::out_of_range("constrained value boundary has been violated" ); |
95 | } |
96 | }; |
97 | |
98 | typedef typename mpl::if_< |
99 | is_base_of< std::exception, exception_type >, |
100 | exception_type, |
101 | exception_wrapper |
102 | >::type actual_exception_type; |
103 | |
104 | public: |
105 | typedef rep_type value_type; |
106 | static rep_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return min_value; } |
107 | static rep_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return max_value; } |
108 | static void on_error(rep_type, rep_type, violation_enum) |
109 | { |
110 | boost::throw_exception(actual_exception_type()); |
111 | } |
112 | }; |
113 | |
114 | |
115 | |
116 | } } //namespace CV |
117 | |
118 | |
119 | |
120 | |
121 | #endif |
122 | |