Add fixed_extent to base::span.
This is done in a more localized way than upstream, where we support
IntegralConstantLike in StrictNumeric.
Bug: none
Change-Id: Ia2a5f086fec0d318f168774aad717805eed25a35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/mini_chromium/+/6090877
Reviewed-by: Mark Mentovai <mark@chromium.org>
diff --git a/base/containers/span.h b/base/containers/span.h
index c7ed4c3..a34d2ee 100644
--- a/base/containers/span.h
+++ b/base/containers/span.h
@@ -33,6 +33,9 @@
namespace base {
+template <size_t N>
+using fixed_extent = std::integral_constant<size_t, N>;
+
template <typename T,
size_t Extent = dynamic_extent,
typename InternalPtrType = T*>
@@ -40,6 +43,21 @@
namespace internal {
+template <typename T>
+concept IntegralConstantLike =
+ std::is_integral_v<decltype(T::value)> &&
+ !std::is_same_v<bool, std::remove_const_t<decltype(T::value)>> &&
+ std::convertible_to<T, decltype(T::value)> &&
+ std::equality_comparable_with<T, decltype(T::value)> &&
+ std::bool_constant<T() == T::value>::value &&
+ std::bool_constant<static_cast<decltype(T::value)>(T()) == T::value>::value;
+
+template <typename T>
+inline constexpr size_t MaybeStaticExt = dynamic_extent;
+template <typename T>
+ requires IntegralConstantLike<T>
+inline constexpr size_t MaybeStaticExt<T> = {T::value};
+
template <typename From, typename To>
concept LegalDataConversion =
std::convertible_to<std::remove_reference_t<From> (*)[],
@@ -260,6 +278,13 @@
requires(N == 0)
= default;
+ template <typename It, size_t N>
+ requires(internal::CompatibleIter<T, It>)
+ UNSAFE_BUFFER_USAGE explicit constexpr span(
+ It first,
+ std::integral_constant<size_t, N> count) noexcept
+ : span(first, N) {}
+
// Constructs a span from a contiguous iterator and a size.
//
// # Checks
@@ -1038,7 +1063,8 @@
// [span.deduct], deduction guides.
template <typename It, typename EndOrSize>
requires(std::contiguous_iterator<It>)
-span(It, EndOrSize) -> span<std::remove_reference_t<std::iter_reference_t<It>>>;
+span(It, EndOrSize) -> span<std::remove_reference_t<std::iter_reference_t<It>>,
+ internal::MaybeStaticExt<EndOrSize>>;
template <
typename R,
