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[span] Conform to the Ranges TS View concept.

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* Allow default construction of spans with fixed-non-zero extent.
* Allow default construction of contiguous_span_iterator and general_span_iterator.
* contiguous_span_iterator members Expect a non-default-initialized object as appropriate.
* value types are never const or volatile - those are object types.
This commit is contained in:
Casey Carter 2016-03-28 23:42:50 -07:00
parent a9f865900d
commit f695ac8bdb
1 changed files with 24 additions and 17 deletions
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41
include/span.h
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@ -1218,10 +1218,6 @@ public:
// default constructor - same as constructing from nullptr_t // default constructor - same as constructing from nullptr_t
constexpr span() noexcept : span(nullptr, bounds_type{}) constexpr span() noexcept : span(nullptr, bounds_type{})
{ {
static_assert(bounds_type::dynamic_rank != 0 ||
(bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
"Default construction of span<T> only possible "
"for dynamic or fixed, zero-length spans.");
} }
// construct from nullptr - get an empty span // construct from nullptr - get an empty span
@ -1983,14 +1979,13 @@ private:
template <class Span> template <class Span>
class contiguous_span_iterator class contiguous_span_iterator
: public std::iterator<std::random_access_iterator_tag, typename Span::value_type>
{ {
using Base = std::iterator<std::random_access_iterator_tag, typename Span::value_type>;
public: public:
using typename Base::reference; using iterator_category = std::random_access_iterator_tag;
using typename Base::pointer; using value_type = typename std::remove_cv<typename Span::value_type>::type;
using typename Base::difference_type; using reference = typename Span::value_type&;
using pointer = typename Span::value_type*;
using difference_type = std::ptrdiff_t;
private: private:
template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions> template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
@ -2000,6 +1995,7 @@ private:
const Span* m_validator; const Span* m_validator;
void validateThis() const void validateThis() const
{ {
Expects(m_validator);
// iterator is out of range of the array // iterator is out of range of the array
Expects(data_ >= m_validator->data_ && data_ < m_validator->data_ + m_validator->size()); Expects(data_ >= m_validator->data_ && data_ < m_validator->data_ + m_validator->size());
} }
@ -2010,6 +2006,11 @@ private:
} }
public: public:
contiguous_span_iterator()
: data_()
, m_validator()
{
}
reference operator*() const noexcept reference operator*() const noexcept
{ {
validateThis(); validateThis();
@ -2022,6 +2023,7 @@ public:
} }
contiguous_span_iterator& operator++() noexcept contiguous_span_iterator& operator++() noexcept
{ {
Expects(m_validator && m_validator->data_ <= data_ && data_ < m_validator->data_ + m_validator->size());
++data_; ++data_;
return *this; return *this;
} }
@ -2033,6 +2035,7 @@ public:
} }
contiguous_span_iterator& operator--() noexcept contiguous_span_iterator& operator--() noexcept
{ {
Expects(m_validator && m_validator->data_ < data_ && data_ <= m_validator->data_ + m_validator->size());
--data_; --data_;
return *this; return *this;
} }
@ -2049,6 +2052,7 @@ public:
} }
contiguous_span_iterator& operator+=(difference_type n) noexcept contiguous_span_iterator& operator+=(difference_type n) noexcept
{ {
Expects(m_validator && m_validator->data_ <= data_ + n && data_ + n <= m_validator->data_ + m_validator->size());
data_ += n; data_ += n;
return *this; return *this;
} }
@ -2094,15 +2098,13 @@ contiguous_span_iterator<Span> operator+(typename contiguous_span_iterator<Span>
template <typename Span> template <typename Span>
class general_span_iterator class general_span_iterator
: public std::iterator<std::random_access_iterator_tag, typename Span::value_type>
{ {
using Base = std::iterator<std::random_access_iterator_tag, typename Span::value_type>;
public: public:
using typename Base::reference; using iterator_category = std::random_access_iterator_tag;
using typename Base::pointer; using value_type = typename std::remove_cv_t<typename Span::value_type>;
using typename Base::difference_type; using reference = typename Span::value_type&;
using typename Base::value_type; using pointer = typename Span::value_type*;
using difference_type = std::ptrdiff_t;
private: private:
template <typename ValueType, size_t Rank> template <typename ValueType, size_t Rank>
@ -2117,6 +2119,11 @@ private:
} }
public: public:
general_span_iterator()
: m_container()
, m_itr()
{
}
reference operator*() noexcept { return (*m_container)[*m_itr]; } reference operator*() noexcept { return (*m_container)[*m_itr]; }
pointer operator->() noexcept { return &(*m_container)[*m_itr]; } pointer operator->() noexcept { return &(*m_container)[*m_itr]; }
general_span_iterator& operator++() noexcept general_span_iterator& operator++() noexcept