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libcamera: span: Make constructors explicit as required by C++20

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The C++20 std::span class, after which Span is modelled, specifies four
constructors as explicit when extent is not dynamic_extent. Align our
implementation with those requirements.

A careful reviewer may notice that this change addresses five
constructors, not four. The reason is that the two constructors taking
Container and const Container parameters are not specified in C++20,
which uses a single constructor taking a range parameter instead. As
ranges are not available in C++17, the Container constructors are our
best effort at providing a similar feature.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
This commit is contained in:
Laurent Pinchart 2020-10-24 19:57:51 +03:00
parent 5e738eb4d5
commit 5aabf85d2c
1 changed files with 43 additions and 31 deletions
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44
include/libcamera/span.h
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@ -113,12 +113,12 @@ public:
{
}
constexpr Span(pointer ptr, [[maybe_unused]] size_type count)
explicit constexpr Span(pointer ptr, [[maybe_unused]] size_type count)
: data_(ptr)
{
}
constexpr Span(pointer first, [[maybe_unused]] pointer last)
explicit constexpr Span(pointer first, [[maybe_unused]] pointer last)
: data_(first)
{
}
@ -154,7 +154,7 @@ public:
}
template<class Container>
constexpr Span(Container &cont,
explicit constexpr Span(Container &cont,
std::enable_if_t<!details::is_span<Container>::value &&
!details::is_array<Container>::value &&
!std::is_array<Container>::value &&
@ -166,7 +166,7 @@ public:
}
template<class Container>
constexpr Span(const Container &cont,
explicit constexpr Span(const Container &cont,
std::enable_if_t<!details::is_span<Container>::value &&
!details::is_array<Container>::value &&
!std::is_array<Container>::value &&
@ -179,7 +179,7 @@ public:
}
template<class U, std::size_t N>
constexpr Span(const Span<U, N> &s,
explicit constexpr Span(const Span<U, N> &s,
std::enable_if_t<std::is_convertible<U (*)[], element_type (*)[]>::value &&
N == Extent,
std::nullptr_t> = nullptr) noexcept
@ -212,24 +212,24 @@ public:
constexpr Span<element_type, Count> first() const
{
static_assert(Count <= Extent, "Count larger than size");
return { data(), Count };
return Span<element_type, Count>{ data(), Count };
}
constexpr Span<element_type, dynamic_extent> first(std::size_t Count) const
{
return { data(), Count };
return Span<element_type, dynamic_extent>{ data(), Count };
}
template<std::size_t Count>
constexpr Span<element_type, Count> last() const
{
static_assert(Count <= Extent, "Count larger than size");
return { data() + size() - Count, Count };
return Span<element_type, Count>{ data() + size() - Count, Count };
}
constexpr Span<element_type, dynamic_extent> last(std::size_t Count) const
{
return { data() + size() - Count, Count };
return Span<element_type, dynamic_extent>{ data() + size() - Count, Count };
}
template<std::size_t Offset, std::size_t Count = dynamic_extent>
@ -238,13 +238,19 @@ public:
static_assert(Offset <= Extent, "Offset larger than size");
static_assert(Count == dynamic_extent || Count + Offset <= Extent,
"Offset + Count larger than size");
return { data() + Offset, Count == dynamic_extent ? size() - Offset : Count };
return Span<element_type, Count != dynamic_extent ? Count : Extent - Offset>{
data() + Offset,
Count == dynamic_extent ? size() - Offset : Count
};
}
constexpr Span<element_type, dynamic_extent>
subspan(std::size_t Offset, std::size_t Count = dynamic_extent) const
{
return { data() + Offset, Count == dynamic_extent ? size() - Offset : Count };
return Span<element_type, dynamic_extent>{
data() + Offset,
Count == dynamic_extent ? size() - Offset : Count
};
}
private:
@ -371,7 +377,7 @@ public:
template<std::size_t Count>
constexpr Span<element_type, Count> first() const
{
return { data(), Count };
return Span<element_type, Count>{ data(), Count };
}
constexpr Span<element_type, dynamic_extent> first(std::size_t Count) const
@ -382,24 +388,30 @@ public:
template<std::size_t Count>
constexpr Span<element_type, Count> last() const
{
return { data() + size() - Count, Count };
return Span<element_type, Count>{ data() + size() - Count, Count };
}
constexpr Span<element_type, dynamic_extent> last(std::size_t Count) const
{
return { data() + size() - Count, Count };
return Span<element_type, dynamic_extent>{ data() + size() - Count, Count };
}
template<std::size_t Offset, std::size_t Count = dynamic_extent>
constexpr Span<element_type, Count> subspan() const
{
return { data() + Offset, Count == dynamic_extent ? size() - Offset : Count };
return Span<element_type, Count>{
data() + Offset,
Count == dynamic_extent ? size() - Offset : Count
};
}
constexpr Span<element_type, dynamic_extent>
subspan(std::size_t Offset, std::size_t Count = dynamic_extent) const
{
return { data() + Offset, Count == dynamic_extent ? size() - Offset : Count };
return Span<element_type, dynamic_extent>{
data() + Offset,
Count == dynamic_extent ? size() - Offset : Count
};
}
private: