// Components for manipulating non-owning sequences of objects -*- C++ -*-
// Copyright (C) 2019-2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library 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; either version 3, or (at your option)
// any later version.
// This library 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.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// .
/** @file span
* This is a Standard C++ Library header.
*/
//
// P0122 span library
// Contributed by ThePhD
//
#ifndef _GLIBCXX_SPAN
#define _GLIBCXX_SPAN 1
#pragma GCC system_header
#if __cplusplus > 201703L
#include
#include
#include
#include
#if __cpp_lib_concepts
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#define __cpp_lib_span 201902L
inline constexpr size_t dynamic_extent = static_cast(-1);
template
class span;
namespace __detail
{
template
struct __is_std_span : false_type { };
template
struct __is_std_span> : true_type { };
template
struct __is_std_array : false_type { };
template
struct __is_std_array<_GLIBCXX_STD_C::array<_Tp, _Num>> : true_type { };
#ifdef _GLIBCXX_DEBUG
template
struct __is_std_array<__debug::array<_Tp, _Num>> : true_type { };
#endif
template
class __extent_storage
{
public:
constexpr
__extent_storage(size_t) noexcept
{ }
static constexpr size_t
_M_extent() noexcept
{ return _Extent; }
};
template<>
class __extent_storage
{
public:
constexpr
__extent_storage(size_t __extent) noexcept
: _M_extent_value(__extent)
{ }
constexpr size_t
_M_extent() const noexcept
{ return this->_M_extent_value; }
private:
size_t _M_extent_value;
};
} // namespace __detail
template
class span
{
template
static constexpr size_t
_S_subspan_extent()
{
if constexpr (_Count != dynamic_extent)
return _Count;
else if constexpr (extent != dynamic_extent)
return _Extent - _Offset;
else
return dynamic_extent;
}
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3255. span's array constructor is too strict
template
using __is_compatible_array = __and_<
bool_constant<(_Extent == dynamic_extent || _ArrayExtent == _Extent)>,
__is_array_convertible<_Type, _Tp>>;
template>
using __is_compatible_iterator = __and_<
bool_constant>,
is_lvalue_reference>,
is_same, remove_cvref_t<_Ref>>,
__is_array_convertible<_Type, remove_reference_t<_Ref>>>;
template
using __is_compatible_range
= __is_compatible_iterator>;
public:
// member types
using value_type = remove_cv_t<_Type>;
using element_type = _Type;
using size_type = size_t;
using reference = element_type&;
using const_reference = const element_type&;
using pointer = _Type*;
using const_pointer = const _Type*;
using iterator
= __gnu_cxx::__normal_iterator;
using const_iterator
= __gnu_cxx::__normal_iterator;
using reverse_iterator = std::reverse_iterator;
using const_reverse_iterator = std::reverse_iterator;
using difference_type = ptrdiff_t;
// member constants
static inline constexpr size_t extent = _Extent;
// constructors
constexpr
span() noexcept
requires ((_Extent + 1u) <= 1u)
: _M_extent(0), _M_ptr(nullptr)
{ }
constexpr
span(const span&) noexcept = default;
template
requires (__is_compatible_array<_Tp, _ArrayExtent>::value)
constexpr
span(_Tp (&__arr)[_ArrayExtent]) noexcept
: span(static_cast(__arr), _ArrayExtent)
{ }
template
requires (__is_compatible_array<_Tp, _ArrayExtent>::value)
constexpr
span(array<_Tp, _ArrayExtent>& __arr) noexcept
: span(static_cast(__arr.data()), _ArrayExtent)
{ }
template
requires (__is_compatible_array::value)
constexpr
span(const array<_Tp, _ArrayExtent>& __arr) noexcept
: span(static_cast(__arr.data()), _ArrayExtent)
{ }
public:
template
requires (_Extent == dynamic_extent)
&& (!__detail::__is_std_span>::value)
&& (!__detail::__is_std_array>::value)
&& (!is_array_v>)
&& (__is_compatible_range<_Range>::value)
constexpr
span(_Range&& __range)
noexcept(noexcept(ranges::data(__range))
&& noexcept(ranges::size(__range)))
: span(ranges::data(__range), ranges::size(__range))
{ }
template _Sentinel>
requires (__is_compatible_iterator<_ContiguousIterator>::value)
&& (!is_convertible_v<_Sentinel, size_type>)
constexpr
span(_ContiguousIterator __first, _Sentinel __last)
noexcept(noexcept(__last - __first))
: _M_extent(static_cast(__last - __first)),
_M_ptr(std::to_address(__first))
{
if (_Extent != dynamic_extent)
__glibcxx_assert((__last - __first) == _Extent);
}
template
requires (__is_compatible_iterator<_ContiguousIterator>::value)
constexpr
span(_ContiguousIterator __first, size_type __count)
noexcept
: _M_extent(__count), _M_ptr(std::to_address(__first))
{ __glibcxx_assert(_Extent == dynamic_extent || __count == _Extent); }
template
requires (_Extent == dynamic_extent || _Extent == _OExtent)
&& (__is_array_convertible<_Type, _OType>::value)
constexpr
span(const span<_OType, _OExtent>& __s) noexcept
: _M_extent(__s.size()), _M_ptr(__s.data())
{ }
// assignment
constexpr span&
operator=(const span&) noexcept = default;
// observers
constexpr size_type
size() const noexcept
{ return this->_M_extent._M_extent(); }
constexpr size_type
size_bytes() const noexcept
{ return this->_M_extent._M_extent() * sizeof(element_type); }
[[nodiscard]] constexpr bool
empty() const noexcept
{ return size() == 0; }
// element access
constexpr reference
front() const noexcept
{
static_assert(extent != 0);
__glibcxx_assert(!empty());
return *this->_M_ptr;
}
constexpr reference
back() const noexcept
{
static_assert(extent != 0);
__glibcxx_assert(!empty());
return *(this->_M_ptr + (size() - 1));
}
constexpr reference
operator[](size_type __idx) const noexcept
{
static_assert(extent != 0);
__glibcxx_assert(__idx < size());
return *(this->_M_ptr + __idx);
}
constexpr pointer
data() const noexcept
{ return this->_M_ptr; }
// iterator support
constexpr iterator
begin() const noexcept
{ return iterator(this->_M_ptr); }
constexpr const_iterator
cbegin() const noexcept
{ return const_iterator(this->_M_ptr); }
constexpr iterator
end() const noexcept
{ return iterator(this->_M_ptr + this->size()); }
constexpr const_iterator
cend() const noexcept
{ return const_iterator(this->_M_ptr + this->size()); }
constexpr reverse_iterator
rbegin() const noexcept
{ return reverse_iterator(this->end()); }
constexpr const_reverse_iterator
crbegin() const noexcept
{ return const_reverse_iterator(this->cend()); }
constexpr reverse_iterator
rend() const noexcept
{ return reverse_iterator(this->begin()); }
constexpr const_reverse_iterator
crend() const noexcept
{ return const_reverse_iterator(this->cbegin()); }
// subviews
template
constexpr span
first() const noexcept
{
if constexpr (_Extent == dynamic_extent)
__glibcxx_assert(_Count <= size());
else
static_assert(_Count <= extent);
return { this->data(), _Count };
}
constexpr span
first(size_type __count) const noexcept
{
__glibcxx_assert(__count <= size());
return { this->data(), __count };
}
template
constexpr span
last() const noexcept
{
if constexpr (_Extent == dynamic_extent)
__glibcxx_assert(_Count <= size());
else
static_assert(_Count <= extent);
return { this->data() + (this->size() - _Count), _Count };
}
constexpr span
last(size_type __count) const noexcept
{
__glibcxx_assert(__count <= size());
return { this->data() + (this->size() - __count), __count };
}
template
constexpr auto
subspan() const noexcept
-> span()>
{
if constexpr (_Extent == dynamic_extent)
__glibcxx_assert(_Offset <= size());
else
static_assert(_Offset <= extent);
if constexpr (_Count == dynamic_extent)
return { this->data() + _Offset, this->size() - _Offset };
else
{
if constexpr (_Extent == dynamic_extent)
{
__glibcxx_assert(_Count <= size());
__glibcxx_assert(_Count <= (size() - _Offset));
}
else
{
static_assert(_Count <= extent);
static_assert(_Count <= (extent - _Offset));
}
return { this->data() + _Offset, _Count };
}
}
constexpr span
subspan(size_type __offset, size_type __count = dynamic_extent) const
noexcept
{
__glibcxx_assert(__offset <= size());
if (__count == dynamic_extent)
__count = this->size() - __offset;
else
{
__glibcxx_assert(__count <= size());
__glibcxx_assert(__offset + __count <= size());
}
return {this->data() + __offset, __count};
}
private:
[[no_unique_address]] __detail::__extent_storage _M_extent;
pointer _M_ptr;
};
// deduction guides
template
span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>;
template
span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>;
template
span(const array<_Type, _ArrayExtent>&)
-> span;
template
span(_Iter, _Sentinel)
-> span>>;
template
span(_Range &&)
-> span>>;
template
inline
span
as_bytes(span<_Type, _Extent> __sp) noexcept
{
return {reinterpret_cast(__sp.data()), __sp.size_bytes()};
}
template
inline
span
as_writable_bytes(span<_Type, _Extent> __sp) noexcept
{
return {reinterpret_cast(__sp.data()), __sp.size_bytes()};
}
// tuple helpers
template
constexpr _Type&
get(span<_Type, _Extent> __sp) noexcept
{
static_assert(_Extent != dynamic_extent && _Index < _Extent,
"get can only be used with a span of non-dynamic (fixed) extent");
return __sp[_Index];
}
template struct tuple_size;
template struct tuple_element;
template
struct tuple_size>
: public integral_constant
{
static_assert(_Extent != dynamic_extent, "tuple_size can only "
"be used with a span of non-dynamic (fixed) extent");
};
template
struct tuple_element<_Index, span<_Type, _Extent>>
{
static_assert(_Extent != dynamic_extent, "tuple_element can only "
"be used with a span of non-dynamic (fixed) extent");
static_assert(_Index < _Extent, "Index is less than Extent");
using type = _Type;
};
namespace ranges
{
template extern inline const bool enable_safe_range;
// Opt-in to safe_range concept
template
inline constexpr bool
enable_safe_range> = true;
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // concepts
#endif // C++20
#endif // _GLIBCXX_SPAN