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almost parity with std::span

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This commit is contained in:
Jordan Maples [MSFT] 2020-02-07 14:09:57 -08:00
parent a49ff1b8df
commit 377b2db537
2 changed files with 94 additions and 29 deletions
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103
include/gsl/span
View File

@ -111,8 +111,7 @@ namespace details
template <std::size_t From, std::size_t To>
struct is_allowed_extent_conversion
: public std::integral_constant<bool, From == To || From == gsl::dynamic_extent ||
To == gsl::dynamic_extent>
: public std::integral_constant<bool, From == To || To == gsl::dynamic_extent>
{
};
@ -301,7 +300,9 @@ namespace details
if (n < 0) Expects(current_ - begin_ >= -n);
}
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
constexpr pointer _Unwrapped() const noexcept
{ // after seeking *this to a high water mark, or using one of the
// _Verify_xxx functions above, unwrap this span_iterator to a raw
@ -316,7 +317,9 @@ namespace details
#else
static constexpr bool _Unwrap_when_unverified = false;
#endif
// clang-format off
GSL_SUPPRESS(con.3) // NO-FORMAT: attribute // TODO: false positive
// clang-format on
constexpr void _Seek_to(const pointer p) noexcept
{ // adjust the position of *this to previously verified location p
// after _Unwrapped
@ -392,7 +395,9 @@ public:
using value_type = std::remove_cv_t<ElementType>;
using size_type = std::size_t;
using pointer = element_type*;
using const_pointer = const element_type*;
using reference = element_type&;
using const_reference = const element_type&;
using difference_type = std::ptrdiff_t;
using iterator = details::span_iterator<ElementType>;
@ -410,38 +415,48 @@ public:
// [span.cons], span constructors, copy, assignment, and destructor
template <bool Dependent = false,
// "Dependent" is needed to make "std::enable_if_t<Dependent || Extent == 0 || Extent == dynamic_extent>" SFINAE,
// since "std::enable_if_t<Extent == 0 || Extent == dynamic_extent>" is ill-formed when Extent is greater than 0.
// "Dependent" is needed to make "std::enable_if_t<Dependent || Extent == 0 || Extent
// == dynamic_extent>" SFINAE, since "std::enable_if_t<Extent == 0 || Extent ==
// dynamic_extent>" is ill-formed when Extent is greater than 0.
class = std::enable_if_t<(Dependent || Extent == 0 || Extent == dynamic_extent)>>
constexpr span() noexcept : storage_(nullptr, details::extent_type<0>())
{}
constexpr span(pointer ptr, size_type count) noexcept : storage_(ptr, count) {}
constexpr span(pointer ptr, size_type count) noexcept : storage_(ptr, count)
{
if (Extent != dynamic_extent) Expects(count == Extent);
}
constexpr span(pointer firstElem, pointer lastElem) noexcept
: storage_(firstElem, static_cast<std::size_t>(std::distance(firstElem, lastElem)))
{}
{
if (Extent != dynamic_extent) { Expects(lastElem - firstElem == Extent); }
}
template <std::size_t N>
constexpr span(element_type (&arr)[N]) noexcept
: storage_(KnownNotNull{std::addressof(arr[0])}, details::extent_type<N>())
{}
template <std::size_t N, class = std::enable_if_t<(N > 0)>>
constexpr span(std::array<std::remove_const_t<element_type>, N>& arr) noexcept
template <std::size_t N, std::size_t Ext = Extent,
std::enable_if_t<(N == Ext || Ext == dynamic_extent), int> = 0>
constexpr span(std::array<value_type, N>& arr) noexcept
: storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
{}
constexpr span(std::array<std::remove_const_t<element_type>, 0>&) noexcept
template <std::size_t N, std::size_t Ext = Extent,
std::enable_if_t<((N == Ext || Ext == dynamic_extent) &&
std::is_convertible<const value_type*, element_type*>::value),
int> = 0>
constexpr span(const std::array<value_type, N>& arr) noexcept
: storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
{}
constexpr span(std::array<value_type, 0>&) noexcept
: storage_(static_cast<pointer>(nullptr), details::extent_type<0>())
{}
template <std::size_t N, class = std::enable_if_t<(N > 0)>>
constexpr span(const std::array<std::remove_const_t<element_type>, N>& arr) noexcept
: storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
{}
constexpr span(const std::array<std::remove_const_t<element_type>, 0>&) noexcept
constexpr span(const std::array<value_type, 0>&) noexcept
: storage_(static_cast<pointer>(nullptr), details::extent_type<0>())
{}
@ -451,8 +466,8 @@ public:
class = std::enable_if_t<
!details::is_span<Container>::value && !details::is_std_array<Container>::value &&
std::is_convertible<typename Container::pointer, pointer>::value &&
std::is_convertible<typename Container::pointer,
decltype(std::declval<Container>().data())>::value>>
std::is_convertible<pointer, typename Container::pointer>::value &&
std::is_convertible<decltype(std::declval<Container&>().data()), pointer>::value>>
constexpr span(Container& cont) noexcept : span(cont.data(), cont.size())
{}
@ -460,10 +475,8 @@ public:
class = std::enable_if_t<
std::is_const<element_type>::value && !details::is_span<Container>::value &&
std::is_convertible<typename Container::pointer, pointer>::value &&
std::is_convertible<typename Container::pointer,
decltype(std::declval<Container>().data())>::value>>
constexpr span(const Container& cont) noexcept
: span(cont.data(), cont.size())
std::is_convertible<decltype(std::declval<Container&>().data()), pointer>::value>>
constexpr span(const Container& cont) noexcept : span(cont.data(), cont.size())
{}
constexpr span(const span& other) noexcept = default;
@ -489,7 +502,9 @@ public:
}
template <std::size_t Count>
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
constexpr span<element_type, Count> last() const noexcept
{
Expects(size() >= Count);
@ -497,7 +512,9 @@ public:
}
template <std::size_t Offset, std::size_t Count = dynamic_extent>
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
constexpr auto subspan() const noexcept ->
typename details::calculate_subspan_type<ElementType, Extent, Offset, Count>::type
{
@ -537,7 +554,9 @@ public:
constexpr bool empty() const noexcept { return size() == 0; }
// [span.elem], span element access
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
constexpr reference operator[](size_type idx) const noexcept
{
Expects(idx < size());
@ -602,7 +621,9 @@ public:
constexpr pointer _Unchecked_begin() const noexcept { return data(); }
constexpr pointer _Unchecked_end() const noexcept
{
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
return data() + size();
}
#endif // _MSC_VER
@ -662,7 +683,9 @@ private:
return tmp.subspan(offset, count);
}
// clang-format off
GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
// clang-format on
span<element_type, dynamic_extent> make_subspan(size_type offset, size_type count,
subspan_selector<dynamic_extent>) const
{
@ -675,6 +698,20 @@ private:
}
};
#if (defined(__cpp_deduction_guides) && (__cpp_deduction_guides >= 201611L))
// Deduction Guides
template <class Type, std::size_t Extent>
span(Type (&)[Extent])->span<Type, Extent>;
template <class Type, std::size_t Size>
span(std::array<Type, Size>&)->span<Type, Size>;
template <class Type, std::size_t Size>
span(const std::array<Type, Size>&)->span<const Type, Size>;
#endif // ( defined(__cpp_deduction_guides) && (__cpp_deduction_guides >= 201611L) )
#if defined(GSL_USE_STATIC_CONSTEXPR_WORKAROUND)
template <class ElementType, std::size_t Extent>
constexpr const typename span<ElementType, Extent>::size_type span<ElementType, Extent>::extent;
@ -742,16 +779,32 @@ template <class ElementType, std::size_t Extent>
span<const byte, details::calculate_byte_size<ElementType, Extent>::value>
as_bytes(span<ElementType, Extent> s) noexcept
{
// clang-format off
GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
// clang-format on
return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
}
template <class ElementType, std::size_t Extent,
class = std::enable_if_t<!std::is_const<ElementType>::value>>
std::enable_if_t<!std::is_const<ElementType>::value, int> = 0>
span<byte, details::calculate_byte_size<ElementType, Extent>::value>
as_writable_bytes(span<ElementType, Extent> s) noexcept
{
// clang-format off
GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
// clang-format on
return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
}
template <class ElementType, std::size_t Extent,
std::enable_if_t<!std::is_const<ElementType>::value, int> = 0>
[[deprecated(
"use as_writable_bytes")]] span<byte, details::calculate_byte_size<ElementType, Extent>::value>
as_writeable_bytes(span<ElementType, Extent> s) noexcept
{
// clang-format off
GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
// clang-format on
return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
}
@ -759,8 +812,7 @@ as_writeable_bytes(span<ElementType, Extent> s) noexcept
// make_span() - Utility functions for creating spans
//
template <class ElementType>
constexpr span<ElementType> make_span(ElementType* ptr,
typename span<ElementType>::size_type count)
constexpr span<ElementType> make_span(ElementType* ptr, typename span<ElementType>::size_type count)
{
return span<ElementType>(ptr, count);
}
@ -812,8 +864,7 @@ constexpr ElementType& at(span<ElementType, Extent> s, index i)
// [span.obs] Free observer functions
template <class ElementType, std::size_t Extent>
constexpr std::ptrdiff_t
ssize(const span<ElementType, Extent>& s) noexcept
constexpr std::ptrdiff_t ssize(const span<ElementType, Extent>& s) noexcept
{
return static_cast<std::ptrdiff_t>(s.size());
}

16
tests/span_tests.cpp
View File

@ -1551,11 +1551,15 @@ TEST(span_test, from_array_constructor)
// even when done dynamically
{
span<int> s = arr;
/*
// this now results in a compile-time error, rather than runtime.
// There is no suitable conversion from dynamic span to fixed span.
auto f = [&]() {
const span<int, 2> s2 = s;
static_cast<void>(s2);
};
EXPECT_DEATH(f(), deathstring);
*/
}
// but doing so explicitly is ok
@ -1570,12 +1574,19 @@ TEST(span_test, from_array_constructor)
static_cast<void>(s1);
}
// ...or dynamically
/*
// this is not a legal operation in std::span, so we are no longer supporting it
// conversion from span<int, 4> to span<int, dynamic_extent> via call to `first`
// then convert from span<int, dynamic_extent> to span<int, 1>
// The dynamic to fixed extents are not supported in the standard
// to make this work, span<int, 1> would need to be span<int>.
{
// NB: implicit conversion to span<int,1> from span<int>
span<int, 1> s1 = s4.first(1);
static_cast<void>(s1);
}
*/
// initialization or assignment to static span that requires size INCREASE is not ok.
int arr2[2] = {1, 2};
@ -1597,12 +1608,15 @@ TEST(span_test, from_array_constructor)
EXPECT_DEATH(f(), deathstring);
}
/*
// This no longer compiles. There is no suitable conversion from dynamic span to a fixed size span.
// this should fail - we are trying to assign a small dynamic span to a fixed_size larger one
span<int> av = arr2; auto f = [&]() {
const span<int, 4> _s4 = av;
static_cast<void>(_s4);
};
EXPECT_DEATH(f(), deathstring);
*/
}
TEST(span_test, interop_with_std_regex)