diff options
Diffstat (limited to 'abseil-cpp/absl/types/span.h')
| -rw-r--r-- | abseil-cpp/absl/types/span.h | 48 |
1 files changed, 35 insertions, 13 deletions
diff --git a/abseil-cpp/absl/types/span.h b/abseil-cpp/absl/types/span.h index 95fe792..70ed8eb 100644 --- a/abseil-cpp/absl/types/span.h +++ b/abseil-cpp/absl/types/span.h @@ -40,7 +40,6 @@ // * `absl::Span` has compiler-provided move and copy constructors and // assignment. This is due to them being specified as `constexpr`, but that // implies const in C++11. -// * `absl::Span` has no `element_type` typedef // * A read-only `absl::Span<const T>` can be implicitly constructed from an // initializer list. // * `absl::Span` has no `bytes()`, `size_bytes()`, `as_bytes()`, or @@ -61,6 +60,7 @@ #include <type_traits> #include <utility> +#include "absl/base/attributes.h" #include "absl/base/internal/throw_delegate.h" #include "absl/base/macros.h" #include "absl/base/optimization.h" @@ -161,15 +161,16 @@ class Span { // Used to SFINAE-enable a function when the slice elements are const. template <typename U> - using EnableIfConstView = + using EnableIfValueIsConst = typename std::enable_if<std::is_const<T>::value, U>::type; // Used to SFINAE-enable a function when the slice elements are mutable. template <typename U> - using EnableIfMutableView = + using EnableIfValueIsMutable = typename std::enable_if<!std::is_const<T>::value, U>::type; public: + using element_type = T; using value_type = absl::remove_cv_t<T>; using pointer = T*; using const_pointer = const T*; @@ -196,13 +197,34 @@ class Span { // Explicit reference constructor for a mutable `Span<T>` type. Can be // replaced with MakeSpan() to infer the type parameter. template <typename V, typename = EnableIfConvertibleFrom<V>, - typename = EnableIfMutableView<V>> - explicit Span(V& v) noexcept // NOLINT(runtime/references) + typename = EnableIfValueIsMutable<V>, + typename = span_internal::EnableIfNotIsView<V>> + explicit Span( + V& v + ABSL_ATTRIBUTE_LIFETIME_BOUND) noexcept // NOLINT(runtime/references) : Span(span_internal::GetData(v), v.size()) {} // Implicit reference constructor for a read-only `Span<const T>` type template <typename V, typename = EnableIfConvertibleFrom<V>, - typename = EnableIfConstView<V>> + typename = EnableIfValueIsConst<V>, + typename = span_internal::EnableIfNotIsView<V>> + constexpr Span( + const V& v + ABSL_ATTRIBUTE_LIFETIME_BOUND) noexcept // NOLINT(runtime/explicit) + : Span(span_internal::GetData(v), v.size()) {} + + // Overloads of the above two functions that are only enabled for view types. + // This is so we can drop the ABSL_ATTRIBUTE_LIFETIME_BOUND annotation. These + // overloads must be made unique by using a different template parameter list + // (hence the = 0 for the IsView enabler). + template <typename V, typename = EnableIfConvertibleFrom<V>, + typename = EnableIfValueIsMutable<V>, + span_internal::EnableIfIsView<V> = 0> + explicit Span(V& v) noexcept // NOLINT(runtime/references) + : Span(span_internal::GetData(v), v.size()) {} + template <typename V, typename = EnableIfConvertibleFrom<V>, + typename = EnableIfValueIsConst<V>, + span_internal::EnableIfIsView<V> = 0> constexpr Span(const V& v) noexcept // NOLINT(runtime/explicit) : Span(span_internal::GetData(v), v.size()) {} @@ -242,9 +264,9 @@ class Span { // Process(ints); // template <typename LazyT = T, - typename = EnableIfConstView<LazyT>> - Span( - std::initializer_list<value_type> v) noexcept // NOLINT(runtime/explicit) + typename = EnableIfValueIsConst<LazyT>> + Span(std::initializer_list<value_type> v + ABSL_ATTRIBUTE_LIFETIME_BOUND) noexcept // NOLINT(runtime/explicit) : Span(v.begin(), v.size()) {} // Accessors @@ -274,8 +296,7 @@ class Span { // // Returns a reference to the i'th element of this span. constexpr reference operator[](size_type i) const noexcept { - // MSVC 2015 accepts this as constexpr, but not ptr_[i] - return ABSL_HARDENING_ASSERT(i < size()), *(data() + i); + return ABSL_HARDENING_ASSERT(i < size()), ptr_[i]; } // Span::at() @@ -398,7 +419,7 @@ class Span { // absl::MakeSpan(vec).subspan(5); // throws std::out_of_range constexpr Span subspan(size_type pos = 0, size_type len = npos) const { return (pos <= size()) - ? Span(data() + pos, span_internal::Min(size() - pos, len)) + ? Span(data() + pos, (std::min)(size() - pos, len)) : (base_internal::ThrowStdOutOfRange("pos > size()"), Span()); } @@ -664,7 +685,8 @@ constexpr Span<T> MakeSpan(T* ptr, size_t size) noexcept { template <int&... ExplicitArgumentBarrier, typename T> Span<T> MakeSpan(T* begin, T* end) noexcept { - return ABSL_HARDENING_ASSERT(begin <= end), Span<T>(begin, end - begin); + return ABSL_HARDENING_ASSERT(begin <= end), + Span<T>(begin, static_cast<size_t>(end - begin)); } template <int&... ExplicitArgumentBarrier, typename C> |