/*
* This file is part of the DXX-Rebirth project <http://www.dxx-rebirth.com/>.
* It is copyright by its individual contributors, as recorded in the
* project's Git history. See COPYING.txt at the top level for license
* terms and a link to the Git history.
*/
#pragma once
#include <type_traits>
#include <utility>
namespace detail {
template <typename T>
struct xrange_is_unsigned : std::is_unsigned<T>
{
/* For the general case, delegate to std::is_unsigned.
* xrange requires that the type not be a reference, so there is no
* need to use std::remove_reference<T> here.
*/
};
template <typename T, T v>
struct xrange_is_unsigned<std::integral_constant<T, v>> : std::is_unsigned<T>
{
/* For the special case that the value is a std::integral_constant,
* examine the underlying integer type.
* std::is_unsigned<std::integral_constant<unsigned, N>> is
* std::false_type, but xrange_is_unsigned should yield
* std::true_type in that case.
*/
};
template <typename B, typename E>
struct xrange_check_constant_endpoints : std::true_type
{
/* By default, endpoints are not constant and are not checked. */
};
template <typename Tb, Tb b, typename Te, Te e>
struct xrange_check_constant_endpoints<std::integral_constant<Tb, b>, std::integral_constant<Te, e>> : std::true_type
{
/* If both endpoints are constant, a static_assert can validate that
* the range is not empty.
*/
static_assert(b < e, "range is always empty due to value of `b` versus value of `e`");
};
}
/* For the general case, store a `const`-qualified copy of the value,
* and provide an implicit conversion.
*/
template <typename T, bool begin>
class xrange_endpoint
{
public:
const T value;
constexpr xrange_endpoint(T v) :
value(v)
{
}
constexpr operator T() const
{
return value;
}
};
/* For the special case that the value is a std::integral_constant,
* inherit from it so that the Empty Base Optimization can apply.
*/
template <typename T, T V, bool begin>
class xrange_endpoint<std::integral_constant<T, V>, begin> : public std::integral_constant<T, V>
{
public:
constexpr xrange_endpoint() = default;
constexpr xrange_endpoint(const std::integral_constant<T, V> &)
{
}
};
template <typename index_type>
class xrange_iterator
{
index_type m_idx;
public:
constexpr xrange_iterator(const index_type i) :
m_idx(i)
{
}
index_type operator*() const
{
return m_idx;
}
xrange_iterator &operator++()
{
++ m_idx;
return *this;
}
constexpr bool operator!=(const xrange_iterator &i) const
{
return m_idx != i.m_idx;
}
};
/* This provides an approximation of the functionality of the Python2
* xrange object. Python3 renamed it to `range`. The older name is
* kept because it is easier to find with grep.
*/
template <typename index_type, typename B = index_type, typename E = index_type>
class xrange :
public xrange_endpoint<B, true>,
public xrange_endpoint<E, false>
{
using begin_type = xrange_endpoint<B, true>;
using end_type = xrange_endpoint<E, false>;
using iterator = xrange_iterator<index_type>;
/* This static_assert has no message, since the value is always
* true. Use of static_assert forces instantiation of the type,
* which has a static_assert that checks the values and displays a
* message on failure.
*/
static_assert(detail::xrange_check_constant_endpoints<B, E>::value);
static_assert(!std::is_reference<E>::value, "xrange<E> must be a value, not a reference");
static begin_type init_begin(B b, E e)
{
if constexpr (std::is_convertible<E, B>::value)
{
#ifdef DXX_CONSTANT_TRUE
(DXX_CONSTANT_TRUE(!(b < e)) && (DXX_ALWAYS_ERROR_FUNCTION(xrange_is_always_empty, "begin never less than end"), 0));
#endif
if (!(b < e))
return e;
}
else
(void)e;
return b;
}
public:
using range_owns_iterated_storage = std::false_type;
xrange(B b, E e) :
begin_type(init_begin(std::move(b), e)), end_type(std::move(e))
{
}
xrange(E e) :
begin_type(), end_type(e)
{
static_assert(detail::xrange_is_unsigned<E>::value, "xrange(E) requires unsigned E; use xrange(B, E) if E must be signed");
}
iterator begin() const
{
return iterator(static_cast<const begin_type &>(*this));
}
iterator end() const
{
return iterator(static_cast<const end_type &>(*this));
}
};
/* Disallow building an `xrange` with a reference to mutable `e` as the
* end term. When `e` is mutable, the loop might change `e` during
* iteration, so using `xrange` could be wrong. If the loop does not
* change `e`, store it in a const qualified variable, which will select
* the next overload down instead.
*/
template <typename Tb, typename Te, typename std::enable_if<!std::is_const<Te>::value, int>::type = 0>
xrange(Tb &&b, Te &e) -> xrange<Tb, Tb, Te &>; // provokes a static_assert failure in the constructor
template <typename Tb, typename Te>
xrange(Tb &&b, Te &&e) -> xrange<
typename std::common_type<Tb, Te>::type,
typename std::remove_const<typename std::remove_reference<Tb>::type>::type,
typename std::remove_const<typename std::remove_reference<Te>::type>::type
>;
template <typename Te>
xrange(const Te &) -> xrange<Te, std::integral_constant<typename std::common_type<Te, unsigned>::type, 0u>>;
template <typename Te>
xrange(Te &) -> xrange<
Te,
std::integral_constant<typename std::common_type<typename std::remove_const<Te>::type, unsigned>::type, 0u>,
Te &
>;
template <typename Te, Te e>
xrange(std::integral_constant<Te, e>) -> xrange<Te, std::integral_constant<Te, Te(0)>, std::integral_constant<Te, e>>;