1 | #ifndef CONSTRAINED_VALUE_HPP___ |
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2 | #define CONSTRAINED_VALUE_HPP___ |
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3 | |
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4 | /* Copyright (c) 2002,2003 CrystalClear Software, Inc. |
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5 | * Use, modification and distribution is subject to the |
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6 | * Boost Software License, Version 1.0. (See accompanying |
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7 | * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) |
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8 | * Author: Jeff Garland |
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9 | * $Date: 2008-11-12 14:37:53 -0500 (Wed, 12 Nov 2008) $ |
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10 | */ |
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11 | |
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12 | #include <exception> |
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13 | #include <stdexcept> |
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14 | #include <boost/config.hpp> |
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15 | #include <boost/throw_exception.hpp> |
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16 | #include <boost/mpl/if.hpp> |
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17 | #include <boost/type_traits/is_base_of.hpp> |
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18 | |
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19 | namespace boost { |
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20 | |
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21 | //! Namespace containing constrained_value template and types |
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22 | namespace CV { |
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23 | //! Represent a min or max violation type |
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24 | enum violation_enum {min_violation, max_violation}; |
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25 | |
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26 | //! A template to specify a constrained basic value type |
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27 | /*! This template provides a quick way to generate |
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28 | * an integer type with a constrained range. The type |
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29 | * provides for the ability to specify the min, max, and |
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30 | * and error handling policy. |
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31 | * |
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32 | * <b>value policies</b> |
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33 | * A class that provides the range limits via the min and |
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34 | * max functions as well as a function on_error that |
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35 | * determines how errors are handled. A common strategy |
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36 | * would be to assert or throw and exception. The on_error |
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37 | * is passed both the current value and the new value that |
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38 | * is in error. |
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39 | * |
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40 | */ |
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41 | template<class value_policies> |
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42 | class constrained_value { |
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43 | public: |
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44 | typedef typename value_policies::value_type value_type; |
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45 | // typedef except_type exception_type; |
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46 | constrained_value(value_type value) : value_((min)()) |
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47 | { |
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48 | assign(value); |
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49 | } |
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50 | constrained_value& operator=(value_type v) |
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51 | { |
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52 | assign(v); |
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53 | return *this; |
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54 | } |
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55 | //! Return the max allowed value (traits method) |
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56 | static value_type max BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::max)();} |
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57 | //! Return the min allowed value (traits method) |
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58 | static value_type min BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::min)();} |
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59 | //! Coerce into the representation type |
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60 | operator value_type() const {return value_;} |
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61 | protected: |
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62 | value_type value_; |
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63 | private: |
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64 | void assign(value_type value) |
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65 | { |
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66 | //adding 1 below gets rid of a compiler warning which occurs when the |
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67 | //min_value is 0 and the type is unsigned.... |
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68 | if (value+1 < (min)()+1) { |
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69 | value_policies::on_error(value_, value, min_violation); |
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70 | return; |
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71 | } |
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72 | if (value > (max)()) { |
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73 | value_policies::on_error(value_, value, max_violation); |
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74 | return; |
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75 | } |
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76 | value_ = value; |
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77 | } |
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78 | }; |
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79 | |
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80 | //! Template to shortcut the constrained_value policy creation process |
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81 | template<typename rep_type, rep_type min_value, |
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82 | rep_type max_value, class exception_type> |
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83 | class simple_exception_policy |
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84 | { |
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85 | struct exception_wrapper : public exception_type |
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86 | { |
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87 | // In order to support throw_exception mechanism in the BOOST_NO_EXCEPTIONS mode, |
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88 | // we'll have to provide a way to acquire std::exception from the exception being thrown. |
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89 | // However, we cannot derive from it, since it would make it interceptable by this class, |
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90 | // which might not be what the user wanted. |
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91 | operator std::out_of_range () const |
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92 | { |
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93 | // TODO: Make the message more descriptive by using arguments to on_error |
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94 | return std::out_of_range("constrained value boundary has been violated"); |
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95 | } |
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96 | }; |
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97 | |
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98 | typedef typename mpl::if_< |
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99 | is_base_of< std::exception, exception_type >, |
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100 | exception_type, |
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101 | exception_wrapper |
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102 | >::type actual_exception_type; |
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103 | |
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104 | public: |
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105 | typedef rep_type value_type; |
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106 | static rep_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return min_value; } |
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107 | static rep_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return max_value; } |
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108 | static void on_error(rep_type, rep_type, violation_enum) |
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109 | { |
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110 | boost::throw_exception(actual_exception_type()); |
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111 | } |
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112 | }; |
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113 | |
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114 | |
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115 | |
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116 | } } //namespace CV |
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117 | |
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118 | |
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119 | |
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120 | |
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121 | #endif |
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