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// Copyright (C) 2012-2021 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef TRIPLET_H
#define TRIPLET_H
#include <exceptions/exceptions.h>
#include <util/optional.h>
namespace isc {
namespace util {
/// @brief This template specifies a parameter value
///
/// This template class is used to store configuration parameters, like lifetime
/// or T1. It defines 3 parameters: min, default, and max value. If the
/// particular configuration parameter is not mandatory, it is possible to
/// mark the parameter described by a @c Triplet "unspecified". For example, the
/// T1 and T2 values in DHCPv4 server are optional and may be not specified
/// in the configuration. The @c Triplets describing these parameters will be
/// marked "unspecified". If the server finds that the particular parameter
/// is unspecified it will not include it (e.g. option 58 or 59) in the message
/// to a client.
///
/// There are 3 constructors:
/// - without parameters - marks the parameter "unspecified"
/// - simple (just one value that sets all parameters)
/// - extended (that sets default value and two thresholds)
///
/// It will be used with integer types. It provides necessary operators, so
/// it can be assigned to a plain integer or integer assigned to a Triplet.
/// See TripletTest.operator test for details on an easy Triplet usage.
template <class T>
class Triplet : public util::Optional<T> {
public:
using util::Optional<T>::get;
/// @brief Base type to Triplet conversion.
///
/// Typically: uint32_t to Triplet assignment. It is very convenient
/// to be able to simply write Triplet<uint32_t> x = 7;
///
/// @param other A number to be assigned as min, max and default value.
Triplet<T>& operator=(T other) {
min_ = other;
util::Optional<T>::default_ = other;
max_ = other;
// The value is now specified because we just assigned one.
util::Optional<T>::unspecified_ = false;
return (*this);
}
/// @brief Constructor without parameters.
///
/// Marks value in @c Triplet unspecified.
Triplet()
: util::Optional<T>(), min_(0), max_(0) {
}
/// @brief Sets a fixed value.
///
/// This constructor assigns a fixed (i.e. no range, just a single value)
/// value.
///
/// @param value A number to be assigned as min, max and default value.
Triplet(T value)
: util::Optional<T>(value), min_(value), max_(value) {
}
/// @brief Sets the default value and thresholds
///
/// @throw BadValue if min <= def <= max rule is violated
Triplet(T min, T def, T max)
: util::Optional<T>(def), min_(min), max_(max) {
if ( (min_ > def) || (def > max_) ) {
isc_throw(BadValue, "Invalid triplet values.");
}
}
/// @brief Returns a minimum allowed value
T getMin() const { return (min_);}
/// @brief Returns value with a hint
///
/// DHCP protocol treats any values sent by a client as hints.
/// This is a method that implements that. We can assign any value
/// from configured range that client asks.
///
/// @param hint A value being returned when if it is within the range
/// between min and max value of @c Triplet. If the hint value is lower
/// than min value, the min value is returned. if the hint is greater
/// than max value, the max value is returned.
///
/// @return A value adjusted to the hint.
T get(T hint) const {
if (hint <= min_) {
return (min_);
}
if (hint >= max_) {
return (max_);
}
return (hint);
}
/// @brief Returns a maximum allowed value
T getMax() const { return (max_); }
private:
/// @brief the minimum value
T min_;
/// @brief the maximum value
T max_;
};
} // namespace isc::dhcp
} // namespace isc
#endif // TRIPLET_H
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