span

This class implements a view in to a range of a C array, etl::array, std::array, etl::vector and std::vector. It will

support construction from any class that supports data() and size() member functions as well as plain C arrays.

The ETL's span adds the ability to access circular iterators that will loop through the span when the beginning or end is

reached. 20.34.0

STL equivalent: std::span.

etl::span<typename T, size_t Extent = etl::dynamic_extent>

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Template deduction guides

C++17

template <typename TIterator>

span(const TIterator begin, const TIterator end)

->span<etl::remove_pointer_t<TIterator>, etl::dynamic_extent>;

template <typename TIterator, typename TSize>

span(const TIterator begin, const TSize size)

->span<etl::remove_pointer_t<TIterator>, etl::dynamic_extent>;

template <typename T, size_t N>

span(T(&)[N])

-> span<T, N>;

template <typename T, size_t N>

span(etl::array<T, N>&)

-> span<T, N>;

template <typename T, size_t N>

span(const etl::array<T, N>&)

-> span<const T, N>;

template <typename T, size_t N>

span(std::array<T, N>&)

->span<T, N>;

template <typename T, size_t N>

span(const std::array<T, N>&)

->span<const T, N>;

Examples

etl::array data{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

etl::span span1{ data };

etl::span span2{ data.begin(), data.end() };

etl::span span3{ data.begin(), data.size() };

etl::span span4{ span1 };

int c_array[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

etl::span span5{ c_array };

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Member types

element_type T

value_type remove_cv<T>::type

size_type size_t

difference_type ptrdiff_t

reference value_type&

const_reference const value_type&

pointer value_type*

const_pointer const value_type*

iterator A random access iterator

reverse_iterator A reverse random access iterator

circular_iterator A circular random access iterator 20.34.0

circular_reverse_iterator A reverse circular random access iterator 20.34.0

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Constructors

ETL_CONSTEXPR span()

Default constructor.

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template <typename TIterator>

ETL_CONSTEXPR span(TIterator begin, TIterator end)

Construct from an iterator or pointer range.

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template <typename TIterator, typename TSize>

ETL_CONSTEXPR span(TIterator begin, TSize size)

Construct from a start and size

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template<const size_t ARRAY_SIZE>

ETL_CONSTEXPR explicit span(element_type(&begin)[ARRAY_SIZE])

Construct from a compile time sized C array.

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template <typename U, size_t N>

ETL_CONSTEXPR span(etl::array<U, N>& a) ETL_NOEXCEPT

Construct from an ETL array.

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template <typename U, size_t N>

ETL_CONSTEXPR span(const etl::array<U, N>& a) ETL_NOEXCEPT

Construct from a const ETL array.

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template <typename U, size_t N>

ETL_CONSTEXPR span(std::array<U, N>& a) ETL_NOEXCEPT

Enabled if ETL_USING_CPP11 and ETL_USING_STL are true.

Construct from an STL array.

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template <typename U, size_t N>

ETL_CONSTEXPR span(const std::array<U, N>& a) ETL_NOEXCEPT

Enabled if ETL_USING_CPP11 and ETL_USING_STL are true.

Construct from a const STL array.

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ETL_CONSTEXPR span(const span& other) ETL_NOEXCEPT

Copy constructor.

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template <typename U, size_t N>

ETL_CONSTEXPR span(const etl::span<U, N>& other) ETL_NOEXCEPT

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Access

ETL_CONSTEXPR reference operator[](size_t i) const

Returns a reference to the indexed element.

Index out of range results in undefined behaviour.

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ETL_NODISCARD ETL_CONSTEXPR reference front() const ETL_NOEXCEPT

Returns a reference to the first element.

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ETL_NODISCARD ETL_CONSTEXPR reference back() const ETL_NOEXCEPT

Returns a reference to the last element.

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ETL_NODISCARD ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT

Returns a pointer to the first element.

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ETL_CONSTEXPR14 span& operator =(const span& other) ETL_NOEXCEPT

Assign from a other span

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template <size_t COUNT>

ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> first() const

Returns a span consisting of the first COUNT elements of the current span

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template <size_t COUNT>

ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> last() const

Returns a span consisting of the last COUNT elements of the current span

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template <size_t OFFSET, size_t COUNT = etl::dynamic_extent>

ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, E> subspan() const

Returns a subspan consisting of the range starting at OFFSET for COUNT elements of the current span

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Iterators

ETL_NODISCARD ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT

Returns an iterator to the beginning of the span.

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ETL_NODISCARD ETL_CONSTEXPR circular_iterator begin_circular() const ETL_NOEXCEPT

Returns a circular iterator to the beginning of the span.

20.34.0

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ETL_NODISCARD ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT

Returns an iterator to the end of the span.

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ETL_NODISCARD ETL_CONSTEXPR iterator rbegin() const ETL_NOEXCEPT

Returns a reverse iterator to the beginning of the span.

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ETL_NODISCARD ETL_CONSTEXPR reverse_circular_iterator rbegin_circular() const ETL_NOEXCEPT

Returns a reverse circular iterator to the beginning of the span.

20.34.0

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ETL_NODISCARD ETL_CONSTEXPR iterator rend() const ETL_NOEXCEPT

Returns a reverse iterator to the end of the span.

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Capacity

ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT

Returns true if the size of the span is zero, otherwise false.

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ETL_NODISCARD ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT

Returns the size of the span.

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ETL_NODISCARD ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT

Returns the size of the span in bytes.

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Non-member functions

template <typename T1, size_t N1, typename T2, size_t N2>

ETL_NODISCARD

ETL_CONSTEXPR

bool operator ==(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs) ETL_NOEXCEPT

20.35.12

Compare two spans for equality.

Returns true if they both point to the same range of data.

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template <typename T1, size_t N1, typename T2, size_t N2>

ETL_NODISCARD

ETL_CONSTEXPR

bool operator !=(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs) ETL_NOEXCEPT

20.35.12

Compare two spans for inequality.

Returns true if they don't both point to the same range of data.

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template <typename T1, size_t N1, typename T2, size_t N2>

bool equal(const etl::span<T1, N1>& lhs, const etl::span<T2, N2>& rhs)

20.35.12

Equality function.

Performs a comparision of the range values.

Returns true if one of the following are true

1. Both spans are empty.

2. They both point to the same range of data.

3. The values in the two ranges are equal.

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Hash

There is a specialisation of etl::hash for etl::span

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Example

Iterating through a span and subspan.

etl::array<int, 10> data = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

using View = etl::span<int>;

View view(data.begin() + 2, data.end() - 2);

void Print(const View& view)

{

for (size_t i = 0; i < view.size(); ++i)

{

std::cout << view[i] << " ";

}

Print(view); // Prints "3 4 5 6 7 8"

auto subview = view.subspan<2, 3>();

Print(subview); // Prints "5 6 7"

size_t hashvalue = etl::hash<View>()(view);

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Looping a span.

etl::array<int, 10> data = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

using View = etl::span<int>;

View view(data.begin(), data.end());

View::circular_iterator itr = view.begin_circular();

// Loop through the data for 1000 iterations.

for (int i; i < 1000; ++i)

{

Print(*itr++);

}

span.h