mirror of
https://github.com/boostorg/safe_numerics.git
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329 lines
8.4 KiB
C++
329 lines
8.4 KiB
C++
#ifndef BOOST_NUMERIC_SAFE_BASE_HPP
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#define BOOST_NUMERIC_SAFE_BASE_HPP
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// MS compatible compilers support #pragma once
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#if defined(_MSC_VER) && (_MSC_VER >= 1020)
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# pragma once
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#endif
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// Copyright (c) 2012 Robert Ramey
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#include <limits>
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#include <type_traits> // is_integral, enable_if
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#include <iosfwd>
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#include <cassert>
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#include <boost/mpl/if.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/identity.hpp>
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#include <boost/mpl/and.hpp>
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#include "concept/integer.hpp"
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#include "concept/exception_policy.hpp"
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#include "concept/promotion_policy.hpp"
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#include "safe_common.hpp"
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#include "exception_policies.hpp"
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#include "boost/concept/assert.hpp"
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namespace boost {
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namespace numeric {
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/////////////////////////////////////////////////////////////////
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// forward declarations to support friend function declarations
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// in safe_base
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template<
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class Stored,
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Stored Min,
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Stored Max,
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class P, // promotion polic
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class E // exception policy
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>
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class safe_base;
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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struct is_safe<safe_base<T, Min, Max, P, E> > : public std::true_type
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{};
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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struct get_promotion_policy<safe_base<T, Min, Max, P, E> > {
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using type = P;
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};
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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struct get_exception_policy<safe_base<T, Min, Max, P, E> > {
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using type = E;
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};
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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struct base_type<safe_base<T, Min, Max, P, E> > {
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using type = T;
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};
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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constexpr T base_value(
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const safe_base<T, Min, Max, P, E> & st
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) {
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return static_cast<T>(st);
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}
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template<
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typename T,
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T N,
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class P, // promotion policy
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class E // exception policy
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>
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class safe_literal_impl;
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/////////////////////////////////////////////////////////////////
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// Main implementation
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template<
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class Stored,
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Stored Min,
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Stored Max,
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class P, // promotion polic
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class E // exception policy
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>
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class safe_base {
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//public:
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BOOST_CONCEPT_ASSERT((Integer<Stored>));
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BOOST_CONCEPT_ASSERT((PromotionPolicy<P>));
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BOOST_CONCEPT_ASSERT((ExceptionPolicy<E>));
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Stored m_t;
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template<
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class CharT,
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class Traits
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>
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friend std::basic_ostream<CharT, Traits> & operator<<(
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std::basic_ostream<CharT, Traits> & os,
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const safe_base & t
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){
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return os << (
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(::std::is_same<Stored, signed char>::value
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|| ::std::is_same<Stored, unsigned char>::value
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|| ::std::is_same<Stored, wchar_t>::value
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) ?
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static_cast<int>(t.m_t)
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:
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t.m_t
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);
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};
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template<
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class CharT,
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class Traits
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>
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friend std::basic_istream<CharT, Traits> & operator>>(
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std::basic_istream<CharT, Traits> & is,
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safe_base & t
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){
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is >> t.m_t;
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t.validated_cast(t.m_t); // no need to store result
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if(is.fail())
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E::domain_error("error in file input");
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return is;
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}
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template<
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class StoredX,
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StoredX MinX,
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StoredX MaxX,
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class PX, // promotion polic
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class EX // exception policy
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>
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friend class safe_base;
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friend class std::numeric_limits<safe_base>;
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template<class T>
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constexpr Stored validated_cast(const T & t) const;
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template<typename T, T N, class P1, class E1>
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constexpr Stored validated_cast(
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const safe_literal_impl<T, N, P1, E1> & t
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) const;
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protected:
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public:
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////////////////////////////////////////////////////////////
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// constructors
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constexpr explicit safe_base(const Stored & rhs, std::false_type);
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// default constructor
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/*
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constexpr explicit safe_base() {
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// this permits creating of invalid instances. This is inline
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// with C++ built-in but violates the premises of the whole library
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// choice are:
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// do nothing - violates premise of he library that all safe objects
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// are valid
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// initialize to valid value - violates C++ behavior of types.
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// add "initialized" flag. Preserves fixes the above, but doubles
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// "overhead"
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// still pending on this.
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}
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*/
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constexpr safe_base() = default;
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template<class T>
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constexpr /*explicit*/ safe_base(const T & t);
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// note: Rule of Five. Don't specify
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// custom constructor, custom destructor, custom assignment
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// custom move, custom move assignment
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// Let the compiler build the defaults.
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public:
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/////////////////////////////////////////////////////////////////
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// casting operators for intrinsic integers
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// convert to any type which is not safe. safe types need to be
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// excluded to prevent ambiguous function selection which
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// would otherwise occur
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template<
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class R,
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typename std::enable_if<
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!boost::numeric::is_safe<R>::value,
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int
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>::type = 0
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>
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constexpr operator R () const;
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constexpr operator Stored () const;
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/////////////////////////////////////////////////////////////////
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// modification binary operators
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template<class T>
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constexpr safe_base & operator=(const T & rhs){
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m_t = validated_cast(rhs);
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return *this;
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}
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template<class T, T MinT, T MaxT, class PT, class ET>
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constexpr safe_base &
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operator=(const safe_base<T, MinT, MaxT, PT, ET> & rhs);
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// mutating unary operators
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safe_base & operator++(){ // pre increment
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return *this = *this + 1;
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}
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safe_base & operator--(){ // pre decrement
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return *this = *this - 1;
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}
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safe_base operator++(int){ // post increment
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safe_base old_t = *this;
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++(*this);
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return old_t;
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}
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safe_base operator--(int){ // post decrement
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safe_base old_t = *this;
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--(*this);
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return old_t;
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}
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// non mutating unary operators
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constexpr safe_base & operator+() const { // unary plus
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return *this;
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}
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// after much consideration, I've permited the resulting value of a unary
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// - to change the type. The C++ standard does invoke integral promotions
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// so it's changing the type as well.
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/* section 5.3.1 &8 of the C++ standard
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The operand of the unary - operator shall have arithmetic or unscoped
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enumeration type and the result is the negation of its operand. Integral
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promotion is performed on integral or enumeration operands. The negative
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of an unsigned quantity is computed by subtracting its value from 2n,
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where n is the number of bits in the promoted operand. The type of the
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result is the type of the promoted operand.
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*/
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constexpr auto operator-() const { // unary minus
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// if this is a unsigned type and the promotion policy is native
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// the result will be unsigned. But then the operation will fail
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// according to the requirements of arithmetic correctness.
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// if this is an unsigned type and the promotion policy is automatic.
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// the result will be signed.
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return 0 - *this;
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}
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/* section 5.3.1 &10 of the C++ standard
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The operand of ~ shall have integral or unscoped enumeration type;
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the result is the ones’ complement of its operand. Integral promotions
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are performed. The type of the result is the type of the promoted operand.
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*/
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constexpr auto operator~() const { // complement
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return ~Stored(0u) ^ *this;
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}
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};
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} // numeric
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} // boost
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/////////////////////////////////////////////////////////////////
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// numeric limits for safe<int> etc.
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#include <limits>
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namespace std {
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template<
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class T,
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T Min,
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T Max,
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class P,
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class E
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>
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class numeric_limits<boost::numeric::safe_base<T, Min, Max, P, E> >
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: public std::numeric_limits<T>
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{
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using SB = boost::numeric::safe_base<T, Min, Max, P, E>;
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public:
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constexpr static SB lowest() noexcept {
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return SB(Min, std::false_type());
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}
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constexpr static SB min() noexcept {
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return SB(Min, std::false_type());
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}
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constexpr static SB max() noexcept {
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return SB(Max, std::false_type());
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}
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};
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} // std
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#endif // BOOST_NUMERIC_SAFE_BASE_HPP
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