Chris@16: #ifndef CONSTRAINED_VALUE_HPP___
Chris@16: #define CONSTRAINED_VALUE_HPP___
Chris@16: 
Chris@16: /* Copyright (c) 2002,2003 CrystalClear Software, Inc.
Chris@16:  * Use, modification and distribution is subject to the 
Chris@16:  * Boost Software License, Version 1.0. (See accompanying
Chris@16:  * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  * Author: Jeff Garland 
Chris@101:  * $Date$
Chris@16:  */
Chris@16: 
Chris@16: #include <exception>
Chris@16: #include <stdexcept>
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/throw_exception.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/type_traits/is_base_of.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //! Namespace containing constrained_value template and types
Chris@16: namespace CV {
Chris@16:   //! Represent a min or max violation type
Chris@16:   enum violation_enum {min_violation, max_violation};
Chris@16:   
Chris@16:   //! A template to specify a constrained basic value type
Chris@16:   /*! This template provides a quick way to generate
Chris@16:    *  an integer type with a constrained range.  The type
Chris@16:    *  provides for the ability to specify the min, max, and
Chris@16:    *  and error handling policy.
Chris@16:    *  
Chris@16:    *  <b>value policies</b>
Chris@16:    *  A class that provides the range limits via the min and
Chris@16:    *  max functions as well as a function on_error that 
Chris@16:    *  determines how errors are handled.  A common strategy
Chris@16:    *  would be to assert or throw and exception.  The on_error
Chris@16:    *  is passed both the current value and the new value that
Chris@16:    *  is in error.
Chris@16:    *
Chris@16:    */
Chris@16:   template<class value_policies>
Chris@16:   class constrained_value {
Chris@16:   public:
Chris@16:     typedef typename value_policies::value_type value_type;
Chris@16:     //    typedef except_type exception_type;
Chris@16:     constrained_value(value_type value) : value_((min)())
Chris@16:     {
Chris@16:       assign(value);
Chris@16:     }
Chris@16:     constrained_value& operator=(value_type v)
Chris@16:     {
Chris@16:       assign(v); 
Chris@16:       return *this;
Chris@16:     }
Chris@16:     //! Return the max allowed value (traits method)
Chris@16:     static value_type max BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::max)();}
Chris@16:     //! Return the min allowed value (traits method)
Chris@16:     static value_type min BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::min)();}
Chris@16:     //! Coerce into the representation type
Chris@16:     operator value_type() const {return value_;}
Chris@16:   protected:
Chris@16:     value_type value_;
Chris@16:   private:
Chris@16:     void assign(value_type value)
Chris@16:     {
Chris@16:       //adding 1 below gets rid of a compiler warning which occurs when the 
Chris@16:       //min_value is 0 and the type is unsigned....
Chris@16:       if (value+1 < (min)()+1) {
Chris@16:         value_policies::on_error(value_, value, min_violation);
Chris@16:         return;
Chris@16:       }
Chris@16:       if (value > (max)()) {
Chris@16:         value_policies::on_error(value_, value, max_violation);
Chris@16:         return;
Chris@16:       }
Chris@16:       value_ = value;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16:   //! Template to shortcut the constrained_value policy creation process
Chris@16:   template<typename rep_type, rep_type min_value, 
Chris@16:            rep_type max_value, class exception_type>
Chris@16:   class simple_exception_policy
Chris@16:   {
Chris@16:     struct exception_wrapper : public exception_type
Chris@16:     {
Chris@16:       // In order to support throw_exception mechanism in the BOOST_NO_EXCEPTIONS mode,
Chris@16:       // we'll have to provide a way to acquire std::exception from the exception being thrown.
Chris@16:       // However, we cannot derive from it, since it would make it interceptable by this class,
Chris@16:       // which might not be what the user wanted.
Chris@16:       operator std::out_of_range () const
Chris@16:       {
Chris@16:         // TODO: Make the message more descriptive by using arguments to on_error
Chris@16:         return std::out_of_range("constrained value boundary has been violated");
Chris@16:       }
Chris@16:     };
Chris@16: 
Chris@16:     typedef typename mpl::if_<
Chris@16:       is_base_of< std::exception, exception_type >,
Chris@16:       exception_type,
Chris@16:       exception_wrapper
Chris@16:     >::type actual_exception_type;
Chris@16: 
Chris@16:   public:
Chris@16:     typedef rep_type value_type;
Chris@16:     static rep_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return min_value; }
Chris@16:     static rep_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return max_value; }
Chris@16:     static void on_error(rep_type, rep_type, violation_enum)
Chris@16:     {
Chris@16:       boost::throw_exception(actual_exception_type());
Chris@16:     }
Chris@16:   };
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: } } //namespace CV
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: 
Chris@16: #endif