mirror of https://github.com/OpenTTD/OpenTTD.git
111 lines
4.2 KiB
C++
111 lines
4.2 KiB
C++
/*
|
|
* This file is part of OpenTTD.
|
|
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
|
|
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
|
|
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
/** @file span_type.hpp Minimized implementation of C++20 std::span. */
|
|
|
|
#ifndef CORE_SPAN_TYPE_HPP
|
|
#define CORE_SPAN_TYPE_HPP
|
|
|
|
/* This is a partial copy/paste from https://github.com/gsl-lite/gsl-lite/blob/master/include/gsl/gsl-lite.hpp */
|
|
|
|
/* Template to check if a template variable defines size() and data(). */
|
|
template <class, class = void>
|
|
struct has_size_and_data : std::false_type{};
|
|
template <class C>
|
|
struct has_size_and_data
|
|
<
|
|
C, std::void_t<
|
|
decltype(std::size(std::declval<C>())),
|
|
decltype(std::data(std::declval<C>()))>
|
|
> : std::true_type{};
|
|
|
|
/* Template to check if two elements are compatible. */
|
|
template <class, class, class = void>
|
|
struct is_compatible_element : std::false_type {};
|
|
template <class C, class E>
|
|
struct is_compatible_element
|
|
<
|
|
C, E, std::void_t<
|
|
decltype(std::data(std::declval<C>())),
|
|
typename std::remove_pointer_t<decltype(std::data( std::declval<C&>()))>(*)[]>
|
|
> : std::is_convertible<typename std::remove_pointer_t<decltype(std::data(std::declval<C&>()))>(*)[], E(*)[]>{};
|
|
|
|
/* Template to check if a container is compatible. gsl-lite also includes is_array and is_std_array, but as we don't use them, they are omitted. */
|
|
template <class C, class E>
|
|
struct is_compatible_container : std::bool_constant
|
|
<
|
|
has_size_and_data<C>::value
|
|
&& is_compatible_element<C, E>::value
|
|
>{};
|
|
|
|
/**
|
|
* A trimmed down version of what std::span will be in C++20.
|
|
*
|
|
* It is fully forwards compatible, so if this codebase switches to C++20,
|
|
* all "span" instances can be replaced by "std::span" without loss of
|
|
* functionality.
|
|
*
|
|
* Currently it only supports basic functionality:
|
|
* - size() and friends
|
|
* - begin() and friends
|
|
*
|
|
* It is meant to simplify function parameters, where we only want to walk
|
|
* a continuous list.
|
|
*/
|
|
template<class T>
|
|
class span {
|
|
public:
|
|
typedef T element_type;
|
|
typedef typename std::remove_cv< T >::type value_type;
|
|
|
|
typedef T &reference;
|
|
typedef T *pointer;
|
|
typedef const T &const_reference;
|
|
typedef const T *const_pointer;
|
|
|
|
typedef pointer iterator;
|
|
typedef const_pointer const_iterator;
|
|
|
|
typedef size_t size_type;
|
|
typedef std::ptrdiff_t difference_type;
|
|
|
|
constexpr span() noexcept : first(nullptr), last(nullptr) {}
|
|
|
|
constexpr span(pointer data_in, size_t size_in) : first(data_in), last(data_in + size_in) {}
|
|
|
|
template<class Container, typename std::enable_if<(is_compatible_container<Container, element_type>::value), int>::type = 0>
|
|
constexpr span(Container &list) noexcept : first(std::data(list)), last(std::data(list) + std::size(list)) {}
|
|
template<class Container, typename std::enable_if<(std::is_const<element_type>::value && is_compatible_container<Container, element_type>::value), int>::type = 0>
|
|
constexpr span(const Container &list) noexcept : first(std::data(list)), last(std::data(list) + std::size(list)) {}
|
|
|
|
constexpr size_t size() const noexcept { return static_cast<size_t>( last - first ); }
|
|
constexpr std::ptrdiff_t ssize() const noexcept { return static_cast<std::ptrdiff_t>( last - first ); }
|
|
constexpr bool empty() const noexcept { return this->size() == 0; }
|
|
|
|
constexpr iterator begin() const noexcept { return iterator(first); }
|
|
constexpr iterator end() const noexcept { return iterator(last); }
|
|
|
|
constexpr const_iterator cbegin() const noexcept { return const_iterator(first); }
|
|
constexpr const_iterator cend() const noexcept { return const_iterator(last); }
|
|
|
|
constexpr reference operator[](size_type idx) const { return first[idx]; }
|
|
|
|
constexpr pointer data() const noexcept { return first; }
|
|
|
|
constexpr span<element_type> subspan(size_t offset, size_t count)
|
|
{
|
|
assert(offset + count <= size());
|
|
return span(this->data() + offset, count);
|
|
}
|
|
|
|
private:
|
|
pointer first;
|
|
pointer last;
|
|
};
|
|
|
|
#endif /* CORE_SPAN_TYPE_HPP */
|