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Merge 5c0aebfcd4 into merged_master (Bitcoin PR #19387)

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This commit is contained in:
Andrew Poelstra 2021-05-07 22:11:23 +00:00
commit 0673bc107b
2 changed files with 43 additions and 4 deletions
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10
src/attributes.h
View file

@ -19,4 +19,14 @@
# endif
#endif
#if defined(__clang__)
# if __has_attribute(lifetimebound)
# define LIFETIMEBOUND [[clang::lifetimebound]]
# else
# define LIFETIMEBOUND
# endif
#else
# define LIFETIMEBOUND
#endif
#endif // BITCOIN_ATTRIBUTES_H

37
src/span.h
View file

@ -18,6 +18,16 @@
#define ASSERT_IF_DEBUG(x)
#endif
#if defined(__clang__)
#if __has_attribute(lifetimebound)
#define SPAN_ATTR_LIFETIMEBOUND [[clang::lifetimebound]]
#else
#define SPAN_ATTR_LIFETIMEBOUND
#endif
#else
#define SPAN_ATTR_LIFETIMEBOUND
#endif
/** A Span is an object that can refer to a contiguous sequence of objects.
*
* It implements a subset of C++20's std::span.
@ -84,6 +94,14 @@ class Span
C* m_data;
std::size_t m_size;
template <class T>
struct is_Span_int : public std::false_type {};
template <class T>
struct is_Span_int<Span<T>> : public std::true_type {};
template <class T>
struct is_Span : public is_Span_int<typename std::remove_cv<T>::type>{};
public:
constexpr Span() noexcept : m_data(nullptr), m_size(0) {}
@ -134,8 +152,19 @@ public:
* To prevent surprises, only Spans for constant value types are supported when passing in temporaries.
* Note that this restriction does not exist when converting arrays or other Spans (see above).
*/
template <typename V, typename std::enable_if<(std::is_const<C>::value || std::is_lvalue_reference<V>::value) && std::is_convertible<typename std::remove_pointer<decltype(std::declval<V&>().data())>::type (*)[], C (*)[]>::value && std::is_convertible<decltype(std::declval<V&>().size()), std::size_t>::value, int>::type = 0>
constexpr Span(V&& v) noexcept : m_data(v.data()), m_size(v.size()) {}
template <typename V>
constexpr Span(V& other SPAN_ATTR_LIFETIMEBOUND,
typename std::enable_if<!is_Span<V>::value &&
std::is_convertible<typename std::remove_pointer<decltype(std::declval<V&>().data())>::type (*)[], C (*)[]>::value &&
std::is_convertible<decltype(std::declval<V&>().size()), std::size_t>::value, std::nullptr_t>::type = nullptr)
: m_data(other.data()), m_size(other.size()){}
template <typename V>
constexpr Span(const V& other SPAN_ATTR_LIFETIMEBOUND,
typename std::enable_if<!is_Span<V>::value &&
std::is_convertible<typename std::remove_pointer<decltype(std::declval<const V&>().data())>::type (*)[], C (*)[]>::value &&
std::is_convertible<decltype(std::declval<const V&>().size()), std::size_t>::value, std::nullptr_t>::type = nullptr)
: m_data(other.data()), m_size(other.size()){}
constexpr C* data() const noexcept { return m_data; }
constexpr C* begin() const noexcept { return m_data; }
@ -192,9 +221,9 @@ public:
/** MakeSpan for arrays: */
template <typename A, int N> Span<A> constexpr MakeSpan(A (&a)[N]) { return Span<A>(a, N); }
/** MakeSpan for temporaries / rvalue references, only supporting const output. */
template <typename V> constexpr auto MakeSpan(V&& v) -> typename std::enable_if<!std::is_lvalue_reference<V>::value, Span<const typename std::remove_pointer<decltype(v.data())>::type>>::type { return std::forward<V>(v); }
template <typename V> constexpr auto MakeSpan(V&& v SPAN_ATTR_LIFETIMEBOUND) -> typename std::enable_if<!std::is_lvalue_reference<V>::value, Span<const typename std::remove_pointer<decltype(v.data())>::type>>::type { return std::forward<V>(v); }
/** MakeSpan for (lvalue) references, supporting mutable output. */
template <typename V> constexpr auto MakeSpan(V& v) -> Span<typename std::remove_pointer<decltype(v.data())>::type> { return v; }
template <typename V> constexpr auto MakeSpan(V& v SPAN_ATTR_LIFETIMEBOUND) -> Span<typename std::remove_pointer<decltype(v.data())>::type> { return v; }
/** Pop the last element off a span, and return a reference to that element. */
template <typename T>