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#ifndef CONSTRAINED_VALUE_HPP___
#define CONSTRAINED_VALUE_HPP___
/* Copyright (c) 2002,2003 CrystalClear Software, Inc.
* Use, modification and distribution is subject to the
* Boost Software License, Version 1.0. (See accompanying
* file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
* Author: Jeff Garland
* $Date: 2008-11-12 14:37:53 -0500 (Wed, 12 Nov 2008) $
*/
#include <exception>
#include <stdexcept>
#include <boost/config.hpp>
#include <boost/throw_exception.hpp>
#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_base_of.hpp>
namespace boost {
//! Namespace containing constrained_value template and types
namespace CV {
//! Represent a min or max violation type
enum violation_enum {min_violation, max_violation};
//! A template to specify a constrained basic value type
/*! This template provides a quick way to generate
* an integer type with a constrained range. The type
* provides for the ability to specify the min, max, and
* and error handling policy.
*
* <b>value policies</b>
* A class that provides the range limits via the min and
* max functions as well as a function on_error that
* determines how errors are handled. A common strategy
* would be to assert or throw and exception. The on_error
* is passed both the current value and the new value that
* is in error.
*
*/
template<class value_policies>
class constrained_value {
public:
typedef typename value_policies::value_type value_type;
// typedef except_type exception_type;
constrained_value(value_type value) : value_((min)())
{
assign(value);
}
constrained_value& operator=(value_type v)
{
assign(v);
return *this;
}
//! Return the max allowed value (traits method)
static value_type max BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::max)();}
//! Return the min allowed value (traits method)
static value_type min BOOST_PREVENT_MACRO_SUBSTITUTION () {return (value_policies::min)();}
//! Coerce into the representation type
operator value_type() const {return value_;}
protected:
value_type value_;
private:
void assign(value_type value)
{
//adding 1 below gets rid of a compiler warning which occurs when the
//min_value is 0 and the type is unsigned....
if (value+1 < (min)()+1) {
value_policies::on_error(value_, value, min_violation);
return;
}
if (value > (max)()) {
value_policies::on_error(value_, value, max_violation);
return;
}
value_ = value;
}
};
//! Template to shortcut the constrained_value policy creation process
template<typename rep_type, rep_type min_value,
rep_type max_value, class exception_type>
class simple_exception_policy
{
struct exception_wrapper : public exception_type
{
// In order to support throw_exception mechanism in the BOOST_NO_EXCEPTIONS mode,
// we'll have to provide a way to acquire std::exception from the exception being thrown.
// However, we cannot derive from it, since it would make it interceptable by this class,
// which might not be what the user wanted.
operator std::out_of_range () const
{
// TODO: Make the message more descriptive by using arguments to on_error
return std::out_of_range("constrained value boundary has been violated");
}
};
typedef typename mpl::if_<
is_base_of< std::exception, exception_type >,
exception_type,
exception_wrapper
>::type actual_exception_type;
public:
typedef rep_type value_type;
static rep_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return min_value; }
static rep_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return max_value; }
static void on_error(rep_type, rep_type, violation_enum)
{
boost::throw_exception(actual_exception_type());
}
};
} } //namespace CV
#endif
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