319 lines
9.9 KiB
C++
319 lines
9.9 KiB
C++
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// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2015, Oracle and/or its affiliates.
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// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
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// Licensed under the Boost Software License version 1.0.
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// http://www.boost.org/users/license.html
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#ifndef BOOST_GEOMETRY_UTIL_PROMOTE_INTEGRAL_HPP
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#define BOOST_GEOMETRY_UTIL_PROMOTE_INTEGRAL_HPP
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// For now deactivate the use of multiprecision integers
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// TODO: activate it later
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#define BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER
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#include <climits>
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#include <cstddef>
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#include <boost/mpl/begin.hpp>
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#include <boost/mpl/deref.hpp>
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#include <boost/mpl/end.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/mpl/list.hpp>
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#include <boost/mpl/next.hpp>
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#include <boost/mpl/size_t.hpp>
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#if !defined(BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER)
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#include <boost/multiprecision/cpp_int.hpp>
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#endif
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#include <boost/type_traits/integral_constant.hpp>
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#include <boost/type_traits/is_fundamental.hpp>
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#include <boost/type_traits/is_integral.hpp>
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#include <boost/type_traits/is_unsigned.hpp>
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namespace boost { namespace geometry
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{
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#ifndef DOXYGEN_NO_DETAIL
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namespace detail { namespace promote_integral
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{
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// meta-function that returns the bit size of a type
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template
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<
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typename T,
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bool IsFundamental = boost::is_fundamental<T>::type::value
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>
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struct bit_size
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{};
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// for fundamental types, just return CHAR_BIT * sizeof(T)
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template <typename T>
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struct bit_size<T, true>
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: boost::mpl::size_t<(CHAR_BIT * sizeof(T))>
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{};
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#if !defined(BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER)
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// partial specialization for cpp_int
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template
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<
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unsigned MinSize,
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unsigned MaxSize,
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boost::multiprecision::cpp_integer_type SignType,
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boost::multiprecision::cpp_int_check_type Checked,
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typename Allocator,
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boost::multiprecision::expression_template_option ExpressionTemplates
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>
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struct bit_size
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<
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boost::multiprecision::number
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<
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boost::multiprecision::cpp_int_backend
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<
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MinSize, MaxSize, SignType, Checked, Allocator
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>,
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ExpressionTemplates
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>,
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false
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> : boost::mpl::size_t<MaxSize>
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{};
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#endif // BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER
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template
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<
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typename T,
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typename Iterator,
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typename EndIterator,
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std::size_t MinSize
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>
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struct promote_to_larger
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{
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typedef typename boost::mpl::deref<Iterator>::type current_type;
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typedef typename boost::mpl::if_c
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<
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(bit_size<current_type>::type::value >= MinSize),
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current_type,
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typename promote_to_larger
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<
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T,
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typename boost::mpl::next<Iterator>::type,
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EndIterator,
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MinSize
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>::type
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>::type type;
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};
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// The following specialization is required to finish the loop over
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// all list elements
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template <typename T, typename EndIterator, std::size_t MinSize>
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struct promote_to_larger<T, EndIterator, EndIterator, MinSize>
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{
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// if promotion fails, keep the number T
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// (and cross fingers that overflow will not occur)
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typedef T type;
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};
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}} // namespace detail::promote_integral
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#endif // DOXYGEN_NO_DETAIL
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/*!
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\brief Meta-function to define an integral type with size
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than is (roughly) twice the bit size of T
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\ingroup utility
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\details
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This meta-function tries to promote the fundamental integral type T
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to a another integral type with size (roughly) twice the bit size of T.
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To do this, two times the bit size of T is tested against the bit sizes of:
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short, int, long, boost::long_long_type, boost::int128_t
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and the one that first matches is chosen.
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For unsigned types the bit size of T is tested against the bit
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sizes of the types above, if T is promoted to a signed type, or
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the bit sizes of
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unsigned short, unsigned int, unsigned long, std::size_t,
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boost::ulong_long_type, boost::uint128_t
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if T is promoted to an unsigned type.
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By default an unsigned type is promoted to a signed type.
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This behavior is controlled by the PromoteUnsignedToUnsigned
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boolean template parameter, whose default value is "false".
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To promote an unsigned type to an unsigned type set the value of
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this template parameter to "true".
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If the macro BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER is not
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defined, boost's multiprecision integer cpp_int<> is used as a
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last resort.
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If BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER is defined and an
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appropriate type cannot be detected, the input type is returned as is.
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Finally, if the passed type is either a floating-point type or a
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user-defined type it is returned as is.
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\note boost::long_long_type and boost::ulong_long_type are
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considered only if the macro BOOST_HAS_LONG_LONG is defined
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\note boost::int128_type and boost::uint128_type are considered
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only if the macros BOOST_HAS_INT128 and BOOST_GEOMETRY_ENABLE_INT128
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are defined
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*/
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template
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<
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typename T,
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bool PromoteUnsignedToUnsigned = false,
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bool UseCheckedInteger = false,
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bool IsIntegral = boost::is_integral<T>::type::value
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>
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class promote_integral
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{
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private:
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static bool const is_unsigned = boost::is_unsigned<T>::type::value;
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typedef detail::promote_integral::bit_size<T> bit_size_type;
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#if !defined(BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER)
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// Define the proper check policy for the multiprecision integer
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typedef typename boost::mpl::if_c
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<
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UseCheckedInteger,
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boost::integral_constant
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<
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boost::multiprecision::cpp_int_check_type,
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boost::multiprecision::checked
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>,
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boost::integral_constant
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<
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boost::multiprecision::cpp_int_check_type,
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boost::multiprecision::unchecked
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>
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>::type check_policy_type;
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// Meta-function to get the multiprecision integer type for the
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// given size and sign type (signed/unsigned)
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template
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<
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unsigned int Size,
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boost::multiprecision::cpp_integer_type SignType
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>
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struct multiprecision_integer_type
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{
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typedef boost::multiprecision::number
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<
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boost::multiprecision::cpp_int_backend
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<
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Size,
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Size,
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SignType,
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check_policy_type::value,
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void
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>
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> type;
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};
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#endif
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// Define the minimum size (in bits) needed for the promoted type
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// If T is the input type and P the promoted type, then the
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// minimum number of bits for P are (below b stands for the number
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// of bits of T):
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// * if T is unsigned and P is unsigned: 2 * b
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// * if T is signed and P is signed: 2 * b - 1
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// * if T is unsigned and P is signed: 2 * b + 1
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typedef typename boost::mpl::if_c
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<
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(PromoteUnsignedToUnsigned && is_unsigned),
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boost::mpl::size_t<(2 * bit_size_type::value)>,
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typename boost::mpl::if_c
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<
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is_unsigned,
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boost::mpl::size_t<(2 * bit_size_type::value + 1)>,
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boost::mpl::size_t<(2 * bit_size_type::value - 1)>
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>::type
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>::type min_bit_size_type;
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// Define the list of signed integral types we are going to use
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// for promotion
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typedef boost::mpl::list
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<
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short, int, long
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#if defined(BOOST_HAS_LONG_LONG)
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, boost::long_long_type
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#endif
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#if defined(BOOST_HAS_INT128) && defined(BOOST_GEOMETRY_ENABLE_INT128)
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, boost::int128_type
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#endif
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#if !defined(BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER)
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, typename multiprecision_integer_type
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<
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min_bit_size_type::value,
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boost::multiprecision::signed_magnitude
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>::type
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#endif
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> signed_integral_types;
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// Define the list of unsigned integral types we are going to use
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// for promotion
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typedef boost::mpl::list
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<
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unsigned short, unsigned int, unsigned long, std::size_t
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#if defined(BOOST_HAS_LONG_LONG)
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, boost::ulong_long_type
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#endif
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#if defined(BOOST_HAS_INT128) && defined(BOOST_GEOMETRY_ENABLE_INT128)
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, boost::uint128_type
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#endif
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#if !defined(BOOST_GEOMETRY_NO_MULTIPRECISION_INTEGER)
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, typename multiprecision_integer_type
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<
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min_bit_size_type::value,
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boost::multiprecision::unsigned_magnitude
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>::type
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#endif
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> unsigned_integral_types;
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// Define the list of integral types that will be used for
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// promotion (depending in whether we was to promote unsigned to
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// unsigned or not)
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typedef typename boost::mpl::if_c
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<
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(is_unsigned && PromoteUnsignedToUnsigned),
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unsigned_integral_types,
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signed_integral_types
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>::type integral_types;
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public:
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typedef typename detail::promote_integral::promote_to_larger
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<
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T,
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typename boost::mpl::begin<integral_types>::type,
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typename boost::mpl::end<integral_types>::type,
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min_bit_size_type::value
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>::type type;
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};
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template <typename T, bool PromoteUnsignedToUnsigned, bool UseCheckedInteger>
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class promote_integral
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<
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T, PromoteUnsignedToUnsigned, UseCheckedInteger, false
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>
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{
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public:
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typedef T type;
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};
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_UTIL_PROMOTE_INTEGRAL_HPP
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