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const bounds_iterator<IndexType>& rhs) noexcept
{
return rhs + n;
}
namespace details
{
template <typename Bounds>
constexpr std::enable_if_t<
std::is_same<typename Bounds::mapping_type, generalized_mapping_tag>::value,
typename Bounds::index_type>
make_stride(const Bounds& bnd) noexcept
{
return bnd.strides();
}
// Make a stride vector from bounds, assuming contiguous memory.
template <typename Bounds>
constexpr std::enable_if_t<
std::is_same<typename Bounds::mapping_type, contiguous_mapping_tag>::value,
typename Bounds::index_type>
make_stride(const Bounds& bnd) noexcept
{
auto extents = bnd.index_bounds();
typename Bounds::size_type stride[Bounds::rank] = {};
stride[Bounds::rank - 1] = 1;
for (size_t i = 1; i < Bounds::rank; ++i) {
stride[Bounds::rank - i - 1] = stride[Bounds::rank - i] * extents[Bounds::rank - i];
}
return {stride};
}
template <typename BoundsSrc, typename BoundsDest>
void verifyBoundsReshape(const BoundsSrc& src, const BoundsDest& dest)
{
static_assert(is_bounds<BoundsSrc>::value && is_bounds<BoundsDest>::value,
"The src type and dest type must be bounds");
static_assert(std::is_same<typename BoundsSrc::mapping_type, contiguous_mapping_tag>::value,
"The source type must be a contiguous bounds");
static_assert(BoundsDest::static_size == dynamic_range ||
BoundsSrc::static_size == dynamic_range ||
BoundsDest::static_size == BoundsSrc::static_size,
"The source bounds must have same size as dest bounds");
Expects(src.size() == dest.size());
}
} // namespace details
template <typename Span>
class contiguous_span_iterator;
template <typename Span>
class general_span_iterator;
template <std::ptrdiff_t DimSize = dynamic_range>
struct dim_t
{
static const std::ptrdiff_t value = DimSize;
};
template <>
struct dim_t<dynamic_range>
{
static const std::ptrdiff_t value = dynamic_range;
const std::ptrdiff_t dvalue;
dim_t(std::ptrdiff_t size) : dvalue(size) {}
};
template <std::ptrdiff_t N>
constexpr std::enable_if_t<(N >= 0), dim_t<N>> dim() noexcept
{
return dim_t<N>();
}
template <std::ptrdiff_t N = dynamic_range>
constexpr std::enable_if_t<N == dynamic_range, dim_t<N>> dim(std::ptrdiff_t n) noexcept
{
return dim_t<>(n);
}
template <typename ValueType, std::ptrdiff_t FirstDimension = dynamic_range,
std::ptrdiff_t... RestDimensions>
class multi_span;
template <typename ValueType, size_t Rank>
class strided_span;
namespace details
{
template <typename T, typename = std::true_type>
struct SpanTypeTraits
{
using value_type = T;
using size_type = size_t;
};
template <typename Traits>
struct SpanTypeTraits<Traits, typename std::is_reference<typename Traits::span_traits&>::type>
{
using value_type = typename Traits::span_traits::value_type;
using size_type = typename Traits::span_traits::size_type;
};
template <typename T, std::ptrdiff_t... Ranks>
struct SpanArrayTraits
{
using type = multi_span<T, Ranks...>;
using value_type = T;
using bounds_type = static_bounds<Ranks...>;
using pointer = T*;
using reference = T&;
};
template <typename T, std::ptrdiff_t N, std::ptrdiff_t... Ranks>
struct SpanArrayTraits<T[N], Ranks...> : SpanArrayTraits<T, Ranks..., N>
{
};
template <typename BoundsType>
BoundsType newBoundsHelperImpl(std::ptrdiff_t totalSize, std::true_type) // dynamic size
{
Expects(totalSize >= 0 && totalSize <= PTRDIFF_MAX);
return BoundsType{totalSize};
}
template <typename BoundsType>
BoundsType newBoundsHelperImpl(std::ptrdiff_t totalSize, std::false_type) // static size
{
Expects(BoundsType::static_size <= totalSize);
return {};
}
template <typename BoundsType>
BoundsType newBoundsHelper(std::ptrdiff_t totalSize)
{
static_assert(BoundsType::dynamic_rank <= 1, "dynamic rank must less or equal to 1");
return newBoundsHelperImpl<BoundsType>(
totalSize, std::integral_constant<bool, BoundsType::dynamic_rank == 1>());
}
struct Sep
{
};
template <typename T, typename... Args>
T static_as_multi_span_helper(Sep, Args... args)
{
return T{narrow_cast<typename T::size_type>(args)...};
}
template <typename T, typename Arg, typename... Args>
std::enable_if_t<
!std::is_same<Arg, dim_t<dynamic_range>>::value && !std::is_same<Arg, Sep>::value, T>
static_as_multi_span_helper(Arg, Args... args)
{
return static_as_multi_span_helper<T>(args...);
}
template <typename T, typename... Args>
T static_as_multi_span_helper(dim_t<dynamic_range> val, Args... args)
{
return static_as_multi_span_helper<T>(args..., val.dvalue);
}
template <typename... Dimensions>
struct static_as_multi_span_static_bounds_helper
{
using type = static_bounds<(Dimensions::value)...>;
};
template <typename T>
struct is_multi_span_oracle : std::false_type
{
};
template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
struct is_multi_span_oracle<multi_span<ValueType, FirstDimension, RestDimensions...>>
: std::true_type
{
};
template <typename ValueType, std::ptrdiff_t Rank>
struct is_multi_span_oracle<strided_span<ValueType, Rank>> : std::true_type
{
};
template <typename T>
struct is_multi_span : is_multi_span_oracle<std::remove_cv_t<T>>
{
};
}
template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
class multi_span
{
// TODO do we still need this?
template <typename ValueType2, std::ptrdiff_t FirstDimension2,
std::ptrdiff_t... RestDimensions2>
friend class multi_span;
public:
using bounds_type = static_bounds<FirstDimension, RestDimensions...>;
static const size_t Rank = bounds_type::rank;
using size_type = typename bounds_type::size_type;
using index_type = typename bounds_type::index_type;
using value_type = ValueType;
using const_value_type = std::add_const_t<value_type>;
using pointer = std::add_pointer_t<value_type>;
using reference = std::add_lvalue_reference_t<value_type>;
using iterator = contiguous_span_iterator<multi_span>;
using const_span = multi_span<const_value_type, FirstDimension, RestDimensions...>;
using const_iterator = contiguous_span_iterator<const_span>;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
using sliced_type =
std::conditional_t<Rank == 1, value_type, multi_span<value_type, RestDimensions...>>;
private:
pointer data_;
bounds_type bounds_;
friend iterator;
friend const_iterator;
public:
// default constructor - same as constructing from nullptr_t
constexpr multi_span() noexcept : multi_span(nullptr, bounds_type{})
{
static_assert(bounds_type::dynamic_rank != 0 ||
(bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
"Default construction of multi_span<T> only possible "
"for dynamic or fixed, zero-length spans.");
}
// construct from nullptr - get an empty multi_span
constexpr multi_span(std::nullptr_t) noexcept : multi_span(nullptr, bounds_type{})
{
static_assert(bounds_type::dynamic_rank != 0 ||
(bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
"nullptr_t construction of multi_span<T> only possible "
"for dynamic or fixed, zero-length spans.");
}
// construct from nullptr with size of 0 (helps with template function calls)
template <class IntType, typename = std::enable_if_t<std::is_integral<IntType>::value>>
constexpr multi_span(std::nullptr_t, IntType size) noexcept : multi_span(nullptr, bounds_type{})
{
static_assert(bounds_type::dynamic_rank != 0 ||
(bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
"nullptr_t construction of multi_span<T> only possible "
"for dynamic or fixed, zero-length spans.");
Expects(size == 0);
}
// construct from a single element
constexpr multi_span(reference data) noexcept : multi_span(&data, bounds_type{1})
{
static_assert(bounds_type::dynamic_rank > 0 || bounds_type::static_size == 0 ||
bounds_type::static_size == 1,
"Construction from a single element only possible "
"for dynamic or fixed spans of length 0 or 1.");
}
// prevent constructing from temporaries for single-elements
constexpr multi_span(value_type&&) = delete;
// construct from pointer + length
constexpr multi_span(pointer ptr, size_type size) noexcept : multi_span(ptr, bounds_type{size})
{
}
// construct from pointer + length - multidimensional
constexpr multi_span(pointer data, bounds_type bounds) noexcept : data_(data),
bounds_(std::move(bounds))
{
Expects((bounds_.size() > 0 && data != nullptr) || bounds_.size() == 0);
}
// construct from begin,end pointer pair
template <typename Ptr,
typename = std::enable_if_t<std::is_convertible<Ptr, pointer>::value &&
details::LessThan<bounds_type::dynamic_rank, 2>::value>>
constexpr multi_span(pointer begin, Ptr end)
: multi_span(begin,
details::newBoundsHelper<bounds_type>(static_cast<pointer>(end) - begin))
{
Expects(begin != nullptr && end != nullptr && begin <= static_cast<pointer>(end));
}
// construct from n-dimensions static array
template <typename T, size_t N, typename Helper = details::SpanArrayTraits<T, N>>
constexpr multi_span(T (&arr)[N])
: multi_span(reinterpret_cast<pointer>(arr), bounds_type{typename Helper::bounds_type{}})
{
static_assert(std::is_convertible<typename Helper::value_type(*)[], value_type(*)[]>::value,
"Cannot convert from source type to target multi_span type.");
static_assert(std::is_convertible<typename Helper::bounds_type, bounds_type>::value,
"Cannot construct a multi_span from an array with fewer elements.");
}
// construct from n-dimensions dynamic array (e.g. new int[m][4])
// (precedence will be lower than the 1-dimension pointer)
template <typename T, typename Helper = details::SpanArrayTraits<T, dynamic_range>>
constexpr multi_span(T* const& data, size_type size)
: multi_span(reinterpret_cast<pointer>(data), typename Helper::bounds_type{size})
{
static_assert(std::is_convertible<typename Helper::value_type(*)[], value_type(*)[]>::value,
"Cannot convert from source type to target multi_span type.");
}
// construct from std::array
template <typename T, size_t N>
constexpr multi_span(std::array<T, N>& arr)
: multi_span(arr.data(), bounds_type{static_bounds<N>{}})
{
static_assert(
std::is_convertible<T(*)[], typename std::remove_const_t<value_type>(*)[]>::value,
"Cannot convert from source type to target multi_span type.");
static_assert(std::is_convertible<static_bounds<N>, bounds_type>::value,
"You cannot construct a multi_span from a std::array of smaller size.");
}
// construct from const std::array
template <typename T, size_t N>
constexpr multi_span(const std::array<std::remove_const_t<value_type>, N>& arr)
: multi_span(arr.data(), static_bounds<N>())
{
static_assert(std::is_convertible<T(*)[], std::remove_const_t<value_type>>::value,
"Cannot convert from source type to target multi_span type.");
static_assert(std::is_convertible<static_bounds<N>, bounds_type>::value,
"You cannot construct a multi_span from a std::array of smaller size.");
}
// prevent constructing from temporary std::array
template <typename T, size_t N>
constexpr multi_span(std::array<T, N>&& arr) = delete;
// construct from containers
// future: could use contiguous_iterator_traits to identify only contiguous containers
// type-requirements: container must have .size(), operator[] which are value_type compatible
template <typename Cont, typename DataType = typename Cont::value_type,
typename = std::enable_if_t<
!details::is_multi_span<Cont>::value &&
std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
*std::declval<Cont>().data())>,
DataType>::value>>
constexpr multi_span(Cont& cont)
: multi_span(static_cast<pointer>(cont.data()),
details::newBoundsHelper<bounds_type>(narrow_cast<size_type>(cont.size())))
{
}
// prevent constructing from temporary containers
template <typename Cont, typename DataType = typename Cont::value_type,
typename = std::enable_if_t<
!details::is_multi_span<Cont>::value &&
std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
*std::declval<Cont>().data())>,
DataType>::value>>
explicit constexpr multi_span(Cont&& cont) = delete;
// construct from a convertible multi_span
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename OtherBounds = static_bounds<OtherDimensions...>,
typename = std::enable_if_t<std::is_convertible<OtherValueType, ValueType>::value &&
std::is_convertible<OtherBounds, bounds_type>::value>>
constexpr multi_span(multi_span<OtherValueType, OtherDimensions...> other) noexcept
: data_(other.data_),
bounds_(other.bounds_)
{
}
// trivial copy and move
#ifndef GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
constexpr multi_span(multi_span&&) = default;
#endif
constexpr multi_span(const multi_span&) = default;
// trivial assignment
#ifndef GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
constexpr multi_span& operator=(multi_span&&) = default;
#endif
constexpr multi_span& operator=(const multi_span&) = default;
// first() - extract the first Count elements into a new multi_span
template <std::ptrdiff_t Count>
constexpr multi_span<ValueType, Count> first() const noexcept
{
static_assert(Count >= 0, "Count must be >= 0.");
static_assert(bounds_type::static_size == dynamic_range ||
Count <= bounds_type::static_size,
"Count is out of bounds.");
Expects(bounds_type::static_size != dynamic_range || Count <= this->size());
return {this->data(), Count};
}
// first() - extract the first count elements into a new multi_span
constexpr multi_span<ValueType, dynamic_range> first(size_type count) const noexcept
{
Expects(count >= 0 && count <= this->size());
return {this->data(), count};
}
// last() - extract the last Count elements into a new multi_span
template <std::ptrdiff_t Count>
constexpr multi_span<ValueType, Count> last() const noexcept
{
static_assert(Count >= 0, "Count must be >= 0.");
static_assert(bounds_type::static_size == dynamic_range ||
Count <= bounds_type::static_size,
"Count is out of bounds.");
Expects(bounds_type::static_size != dynamic_range || Count <= this->size());
return {this->data() + this->size() - Count, Count};
}
// last() - extract the last count elements into a new multi_span
constexpr multi_span<ValueType, dynamic_range> last(size_type count) const noexcept
{
Expects(count >= 0 && count <= this->size());
return {this->data() + this->size() - count, count};
}
// subspan() - create a subview of Count elements starting at Offset
template <std::ptrdiff_t Offset, std::ptrdiff_t Count>
constexpr multi_span<ValueType, Count> subspan() const noexcept
{
static_assert(Count >= 0, "Count must be >= 0.");
static_assert(Offset >= 0, "Offset must be >= 0.");
static_assert(bounds_type::static_size == dynamic_range ||
((Offset <= bounds_type::static_size) &&
Count <= bounds_type::static_size - Offset),
"You must describe a sub-range within bounds of the multi_span.");
Expects(bounds_type::static_size != dynamic_range ||
(Offset <= this->size() && Count <= this->size() - Offset));
return {this->data() + Offset, Count};
}
// subspan() - create a subview of count elements starting at offset
// supplying dynamic_range for count will consume all available elements from offset
constexpr multi_span<ValueType, dynamic_range> subspan(size_type offset,
size_type count = dynamic_range) const
noexcept
{
Expects((offset >= 0 && offset <= this->size()) &&
(count == dynamic_range || (count <= this->size() - offset)));
return {this->data() + offset, count == dynamic_range ? this->length() - offset : count};
}
// section - creates a non-contiguous, strided multi_span from a contiguous one
constexpr strided_span<ValueType, Rank> section(index_type origin, index_type extents) const
noexcept
{
size_type size = this->bounds().total_size() - this->bounds().linearize(origin);
return {&this->operator[](origin), size,
strided_bounds<Rank>{extents, details::make_stride(bounds())}};
}
// length of the multi_span in elements
constexpr size_type size() const noexcept { return bounds_.size(); }
// length of the multi_span in elements
constexpr size_type length() const noexcept { return this->size(); }
// length of the multi_span in bytes
constexpr size_type size_bytes() const noexcept { return sizeof(value_type) * this->size(); }
// length of the multi_span in bytes
constexpr size_type length_bytes() const noexcept { return this->size_bytes(); }
constexpr bool empty() const noexcept { return this->size() == 0; }
static constexpr std::size_t rank() { return Rank; }
template <size_t Dim = 0>
constexpr size_type extent() const noexcept
{
static_assert(Dim < Rank,
"Dimension should be less than rank (dimension count starts from 0).");
return bounds_.template extent<Dim>();
}
template <typename IntType>
constexpr size_type extent(IntType dim) const noexcept
{
return bounds_.extent(dim);
}
constexpr bounds_type bounds() const noexcept { return bounds_; }
constexpr pointer data() const noexcept { return data_; }
template <typename FirstIndex>
constexpr reference operator()(FirstIndex index)
{
return this->operator[](narrow_cast<std::ptrdiff_t>(index));
}
template <typename FirstIndex, typename... OtherIndices>
constexpr reference operator()(FirstIndex index, OtherIndices... indices)
{
index_type idx = {narrow_cast<std::ptrdiff_t>(index),
narrow_cast<std::ptrdiff_t>(indices...)};
return this->operator[](idx);
}
constexpr reference operator[](const index_type& idx) const noexcept
{
return data_[bounds_.linearize(idx)];
}
template <bool Enabled = (Rank > 1), typename Ret = std::enable_if_t<Enabled, sliced_type>>
constexpr Ret operator[](size_type idx) const noexcept
{
Expects(idx < bounds_.size()); // index is out of bounds of the array
const size_type ridx = idx * bounds_.stride();
// index is out of bounds of the underlying data
Expects(ridx < bounds_.total_size());
return Ret{data_ + ridx, bounds_.slice()};
}
constexpr iterator begin() const noexcept { return iterator{this, true}; }
constexpr iterator end() const noexcept { return iterator{this, false}; }
constexpr const_iterator cbegin() const noexcept
{
return const_iterator{reinterpret_cast<const const_span*>(this), true};
}
constexpr const_iterator cend() const noexcept
{
return const_iterator{reinterpret_cast<const const_span*>(this), false};
}
constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
constexpr const_reverse_iterator crbegin() const noexcept
{
return const_reverse_iterator{cend()};
}
constexpr const_reverse_iterator crend() const noexcept
{
return const_reverse_iterator{cbegin()};
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator==(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return bounds_.size() == other.bounds_.size() &&
(data_ == other.data_ || std::equal(this->begin(), this->end(), other.begin()));
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator!=(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return !(*this == other);
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator<(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return std::lexicographical_compare(this->begin(), this->end(), other.begin(), other.end());
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator<=(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return !(other < *this);
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator>(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return (other < *this);
}
template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator>=(const multi_span<OtherValueType, OtherDimensions...>& other) const
noexcept
{
return !(*this < other);
}
};
//
// Free functions for manipulating spans
//
// reshape a multi_span into a different dimensionality
// DimCount and Enabled here are workarounds for a bug in MSVC 2015
template <typename SpanType, typename... Dimensions2, size_t DimCount = sizeof...(Dimensions2),
bool Enabled = (DimCount > 0), typename = std::enable_if_t<Enabled>>
constexpr auto as_multi_span(SpanType s, Dimensions2... dims)
-> multi_span<typename SpanType::value_type, Dimensions2::value...>
{
static_assert(details::is_multi_span<SpanType>::value,
"Variadic as_multi_span() is for reshaping existing spans.");
using BoundsType =
typename multi_span<typename SpanType::value_type, (Dimensions2::value)...>::bounds_type;
auto tobounds = details::static_as_multi_span_helper<BoundsType>(dims..., details::Sep{});
details::verifyBoundsReshape(s.bounds(), tobounds);
return {s.data(), tobounds};
}
// convert a multi_span<T> to a multi_span<const byte>
template <typename U, std::ptrdiff_t... Dimensions>
multi_span<const byte, dynamic_range> as_bytes(multi_span<U, Dimensions...> s) noexcept
{
static_assert(std::is_trivial<std::decay_t<U>>::value,
"The value_type of multi_span must be a trivial type.");
return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
}
// convert a multi_span<T> to a multi_span<byte> (a writeable byte multi_span)
// this is not currently a portable function that can be relied upon to work
// on all implementations. It should be considered an experimental extension
// to the standard GSL interface.
template <typename U, std::ptrdiff_t... Dimensions>
multi_span<byte> as_writeable_bytes(multi_span<U, Dimensions...> s) noexcept
{
static_assert(std::is_trivial<std::decay_t<U>>::value,
"The value_type of multi_span must be a trivial type.");
return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
}
// convert a multi_span<const byte> to a multi_span<const T>
// this is not currently a portable function that can be relied upon to work
// on all implementations. It should be considered an experimental extension
// to the standard GSL interface.
template <typename U, std::ptrdiff_t... Dimensions>
constexpr auto as_multi_span(multi_span<const byte, Dimensions...> s) noexcept -> multi_span<
const U, static_cast<std::ptrdiff_t>(
multi_span<const byte, Dimensions...>::bounds_type::static_size != dynamic_range
? (static_cast<size_t>(
multi_span<const byte, Dimensions...>::bounds_type::static_size) /
sizeof(U))
: dynamic_range)>
{
using ConstByteSpan = multi_span<const byte, Dimensions...>;
static_assert(
std::is_trivial<std::decay_t<U>>::value &&
(ConstByteSpan::bounds_type::static_size == dynamic_range ||
ConstByteSpan::bounds_type::static_size % narrow_cast<std::ptrdiff_t>(sizeof(U)) == 0),
"Target type must be a trivial type and its size must match the byte array size");
Expects((s.size_bytes() % sizeof(U)) == 0 && (s.size_bytes() / sizeof(U)) < PTRDIFF_MAX);
return {reinterpret_cast<const U*>(s.data()),
s.size_bytes() / narrow_cast<std::ptrdiff_t>(sizeof(U))};
}
// convert a multi_span<byte> to a multi_span<T>
// this is not currently a portable function that can be relied upon to work
// on all implementations. It should be considered an experimental extension
// to the standard GSL interface.
template <typename U, std::ptrdiff_t... Dimensions>
constexpr auto as_multi_span(multi_span<byte, Dimensions...> s) noexcept
-> multi_span<U, narrow_cast<std::ptrdiff_t>(
multi_span<byte, Dimensions...>::bounds_type::static_size != dynamic_range
? static_cast<std::size_t>(
multi_span<byte, Dimensions...>::bounds_type::static_size) /
sizeof(U)
: dynamic_range)>
{
using ByteSpan = multi_span<byte, Dimensions...>;
static_assert(
std::is_trivial<std::decay_t<U>>::value &&
(ByteSpan::bounds_type::static_size == dynamic_range ||
ByteSpan::bounds_type::static_size % static_cast<std::size_t>(sizeof(U)) == 0),
"Target type must be a trivial type and its size must match the byte array size");
Expects((s.size_bytes() % sizeof(U)) == 0);
return {reinterpret_cast<U*>(s.data()),
s.size_bytes() / narrow_cast<std::ptrdiff_t>(sizeof(U))};
}
template <typename T, std::ptrdiff_t... Dimensions>
constexpr auto as_multi_span(T* const& ptr, dim_t<Dimensions>... args)
-> multi_span<std::remove_all_extents_t<T>, Dimensions...>
{
return {reinterpret_cast<std::remove_all_extents_t<T>*>(ptr),
details::static_as_multi_span_helper<static_bounds<Dimensions...>>(args...,
details::Sep{})};
}
template <typename T>
constexpr auto as_multi_span(T* arr, std::ptrdiff_t len) ->
typename details::SpanArrayTraits<T, dynamic_range>::type
{
return {reinterpret_cast<std::remove_all_extents_t<T>*>(arr), len};
}
template <typename T, size_t N>
constexpr auto as_multi_span(T (&arr)[N]) -> typename details::SpanArrayTraits<T, N>::type
{
return {arr};
}
template <typename T, size_t N>
constexpr multi_span<const T, N> as_multi_span(const std::array<T, N>& arr)
{
return {arr};
}
template <typename T, size_t N>
constexpr multi_span<const T, N> as_multi_span(const std::array<T, N>&&) = delete;
template <typename T, size_t N>
constexpr multi_span<T, N> as_multi_span(std::array<T, N>& arr)
{
return {arr};
}
template <typename T>
constexpr multi_span<T, dynamic_range> as_multi_span(T* begin, T* end)
{
return {begin, end};
}
template <typename Cont>
constexpr auto as_multi_span(Cont& arr) -> std::enable_if_t<
!details::is_multi_span<std::decay_t<Cont>>::value,
multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>>
{
Expects(arr.size() < PTRDIFF_MAX);
return {arr.data(), narrow_cast<std::ptrdiff_t>(arr.size())};
}
template <typename Cont>
constexpr auto as_multi_span(Cont&& arr) -> std::enable_if_t<
!details::is_multi_span<std::decay_t<Cont>>::value,
multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>> = delete;
// from basic_string which doesn't have nonconst .data() member like other contiguous containers
template <typename CharT, typename Traits, typename Allocator>
constexpr auto as_multi_span(std::basic_string<CharT, Traits, Allocator>& str)
-> multi_span<CharT, dynamic_range>
{
Expects(str.size() < PTRDIFF_MAX);
return {&str[0], narrow_cast<std::ptrdiff_t>(str.size())};
}
// strided_span is an extension that is not strictly part of the GSL at this time.
// It is kept here while the multidimensional interface is still being defined.
template <typename ValueType, size_t Rank>
class strided_span
{
public:
using bounds_type = strided_bounds<Rank>;
using size_type = typename bounds_type::size_type;
using index_type = typename bounds_type::index_type;
using value_type = ValueType;
using const_value_type = std::add_const_t<value_type>;
using pointer = std::add_pointer_t<value_type>;
using reference = std::add_lvalue_reference_t<value_type>;
using iterator = general_span_iterator<strided_span>;
using const_strided_span = strided_span<const_value_type, Rank>;
using const_iterator = general_span_iterator<const_strided_span>;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
using sliced_type =
std::conditional_t<Rank == 1, value_type, strided_span<value_type, Rank - 1>>;
private:
pointer data_;
bounds_type bounds_;
friend iterator;
friend const_iterator;
template <typename OtherValueType, size_t OtherRank>
friend class strided_span;
public:
// from raw data
constexpr strided_span(pointer ptr, size_type size, bounds_type bounds)
: data_(ptr), bounds_(std::move(bounds))
{
Expects((bounds_.size() > 0 && ptr != nullptr) || bounds_.size() == 0);
// Bounds cross data boundaries
Expects(this->bounds().total_size() <= size);
(void) size;
}
// from static array of size N
template <size_type N>
constexpr strided_span(value_type (&values)[N], bounds_type bounds)
: strided_span(values, N, std::move(bounds))
{
}
// from array view
template <typename OtherValueType, std::ptrdiff_t... Dimensions,
bool Enabled1 = (sizeof...(Dimensions) == Rank),
bool Enabled2 = std::is_convertible<OtherValueType*, ValueType*>::value,
typename Dummy = std::enable_if_t<Enabled1 && Enabled2>>
constexpr strided_span(multi_span<OtherValueType, Dimensions...> av, bounds_type bounds)
: strided_span(av.data(), av.bounds().total_size(), std::move(bounds))
{
}
// convertible
template <typename OtherValueType, typename Dummy = std::enable_if_t<std::is_convertible<
OtherValueType (*)[], value_type (*)[]>::value>>
constexpr strided_span(const strided_span<OtherValueType, Rank>& other)
: data_(other.data_), bounds_(other.bounds_)
{
}
// convert from bytes
template <typename OtherValueType>
constexpr strided_span<
typename std::enable_if<std::is_same<value_type, const byte>::value, OtherValueType>::type,
Rank>
as_strided_span() const
{
static_assert((sizeof(OtherValueType) >= sizeof(value_type)) &&
(sizeof(OtherValueType) % sizeof(value_type) == 0),
"OtherValueType should have a size to contain a multiple of ValueTypes");
auto d = narrow_cast<size_type>(sizeof(OtherValueType) / sizeof(value_type));
size_type size = this->bounds().total_size() / d;
return {const_cast<OtherValueType*>(reinterpret_cast<const OtherValueType*>(this->data())),
size, bounds_type{resize_extent(this->bounds().index_bounds(), d),
resize_stride(this->bounds().strides(), d)}};
}
constexpr strided_span section(index_type origin, index_type extents) const
{
size_type size = this->bounds().total_size() - this->bounds().linearize(origin);
return {&this->operator[](origin), size,
bounds_type{extents, details::make_stride(bounds())}};
}
constexpr reference operator[](const index_type& idx) const
{
return data_[bounds_.linearize(idx)];
}
template <bool Enabled = (Rank > 1), typename Ret = std::enable_if_t<Enabled, sliced_type>>
constexpr Ret operator[](size_type idx) const
{
Expects(idx < bounds_.size()); // index is out of bounds of the array
const size_type ridx = idx * bounds_.stride();
// index is out of bounds of the underlying data
Expects(ridx < bounds_.total_size());
return {data_ + ridx, bounds_.slice().total_size(), bounds_.slice()};
}
constexpr bounds_type bounds() const noexcept { return bounds_; }
template <size_t Dim = 0>
constexpr size_type extent() const noexcept
{
static_assert(Dim < Rank,
"dimension should be less than Rank (dimension count starts from 0)");
return bounds_.template extent<Dim>();
}
constexpr size_type size() const noexcept { return bounds_.size(); }
constexpr pointer data() const noexcept { return data_; }
constexpr explicit operator bool() const noexcept { return data_ != nullptr; }
constexpr iterator begin() const { return iterator{this, true}; }
constexpr iterator end() const { return iterator{this, false}; }
constexpr const_iterator cbegin() const
{
return const_iterator{reinterpret_cast<const const_strided_span*>(this), true};
}
constexpr const_iterator cend() const
{
return const_iterator{reinterpret_cast<const const_strided_span*>(this), false};
}
constexpr reverse_iterator rbegin() const { return reverse_iterator{end()}; }
constexpr reverse_iterator rend() const { return reverse_iterator{begin()}; }
constexpr const_reverse_iterator crbegin() const { return const_reverse_iterator{cend()}; }
constexpr const_reverse_iterator crend() const { return const_reverse_iterator{cbegin()}; }
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator==(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return bounds_.size() == other.bounds_.size() &&
(data_ == other.data_ || std::equal(this->begin(), this->end(), other.begin()));
}
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator!=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return !(*this == other);
}
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator<(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return std::lexicographical_compare(this->begin(), this->end(), other.begin(), other.end());
}
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator<=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return !(other < *this);
}
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator>(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return (other < *this);
}
template <typename OtherValueType, std::ptrdiff_t OtherRank,
typename Dummy = std::enable_if_t<std::is_same<
std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
constexpr bool operator>=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
{
return !(*this < other);
}
private:
static index_type resize_extent(const index_type& extent, std::ptrdiff_t d)
{
// The last dimension of the array needs to contain a multiple of new type elements
Expects(extent[Rank - 1] >= d && (extent[Rank - 1] % d == 0));
index_type ret = extent;
ret[Rank - 1] /= d;
return ret;
}
template <bool Enabled = (Rank == 1), typename Dummy = std::enable_if_t<Enabled>>
static index_type resize_stride(const index_type& strides, std::ptrdiff_t, void* = 0)
{
// Only strided arrays with regular strides can be resized
Expects(strides[Rank - 1] == 1);
return strides;
}
template <bool Enabled = (Rank > 1), typename Dummy = std::enable_if_t<Enabled>>
static index_type resize_stride(const index_type& strides, std::ptrdiff_t d)
{
// Only strided arrays with regular strides can be resized
Expects(strides[Rank - 1] == 1);
// The strides must have contiguous chunks of
// memory that can contain a multiple of new type elements
Expects(strides[Rank - 2] >= d && (strides[Rank - 2] % d == 0));
for (size_t i = Rank - 1; i > 0; --i) {
// Only strided arrays with regular strides can be resized
Expects((strides[i - 1] >= strides[i]) && (strides[i - 1] % strides[i] == 0));
}
index_type ret = strides / d;
ret[Rank - 1] = 1;
return ret;
}
};
template <class Span>
class contiguous_span_iterator
: public std::iterator<std::random_access_iterator_tag, typename Span::value_type>