etl/docs/containers/Views/array-wrapper.md

title
array_wrapper

{{< callout >}} Header: array_wrapper.h
Since: All versions
{{< /callout >}}

This class implements a zero cost C++ interface around a const or non-const C array. It presents the same API as std::array. It allows legacy C data to be more easily integrated with C++ interfaces and be accessed in a less error prone fashion. If C++11 or above is supported then most functions can be 'constexpr'.

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Member types

value_type
size_type
difference_type
reference
value_type
reference
const_reference
pointer
const_pointer
iterator
const_iterator
reverse_iterator
const_reverse_iterator

Member constants

May be used as indexes in to the array.

SIZE = Size of the array
MAX_SIZE = SIZE
FRONT = 0
BACK = SIZE - 1
BEGIN = 0
END = SIZE
RBEGIN = SIZE - 1
REND = -1

Element access

T& at(size_t i)

ETL_CONSTEXPR const T& at(size_t i) const

Description
Returns a reference or const reference to the indexed element.
Emits an etl::array_wrapper_bounds if the index isout of range of the array.
If asserts or exceptions are not enabled then undefined behaviour occurs.

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T& operator[](size_t i)

ETL_CONSTEXPR const T& operator[](size_t i) const

Description
Returns a reference or const reference to the indexed element.if the index is out of range of the array then undefined behaviour occurs.---

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T& front()

ETL_CONSTEXPR const T& front() const

Description
Returns a reference or const reference to the first element.---

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T& back()

ETL_CONSTEXPR const T& back() const

Description
Returns a reference or const reference to the last element.---

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T* data()

ETL_CONSTEXPR const T* data() const

Description
Returns a pointer or const pointer to the array.---Modifiers

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void fill(parameter_t value)

Description
Fill a non-cost array with the value.---

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template <typename T, T(&ARRAYOTHER)[SIZE_]>
void swap(etl::array_wrapper<T, SIZE_, ARRAYOTHER>& other)

Description
Swaps the array contents with another.---Iterators

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ETL_CONSTEXPR iterator begin()

ETL_CONSTEXPR const_iterator begin() constETL_CONSTEXPR const_iterator cbegin() const

Description
Returns an iterator to the beginning of the array.---

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ETL_CONSTEXPR iterator end()

ETL_CONSTEXPR const_iterator end() constETL_CONSTEXPR const_iterator cend() const

Description
Returns an iterator to the end of the array.---

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ETL_CONSTEXPR iterator rbegin()

ETL_CONSTEXPR const_reverse_iterator rbegin() const

ETL_CONSTEXPR const_reverse_iterator crbegin() const

Description
Returns a reverse iterator to the beginning of the array.---

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ETL_CONSTEXPR iterator rend()

ETL_CONSTEXPR const_reverse_iterator rend() constETL_CONSTEXPR const_reverse_iterator crend() const

Description
Returns a reverse iterator to the end of the array.---Capacity

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ETL_CONSTEXPR size_t size() const

Description
Returns the size of the view.---

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ETL_CONSTEXPR size_t max_size() const

Description
Returns the maximum possible size of the view.---Non-member functions

Lexicographically comparisons

operator ==
Returns
true if the contents of the array views are equal, otherwise false.

operator !=
Returns
true if the contents of the array views are not equal, otherwise false.

operator <
Returns
true if the contents of the lhs are lexicographically less than the
contents of the rhs, otherwise false.

operator <=
Returns
true if the contents of the lhs are lexicographically less than or equal to the
contents of the rhs, otherwise false.

operator >
Returns
true if the contents of the lhs are lexicographically greater than the
contents of the rhs, otherwise false.

operator >=
Returns
true if the contents of the lhs are lexicographically greater than or equal to the
contents of the rhs, otherwise false

Swap

template <typename T, std::size_t SIZE, T(&ARRAYL)[SIZE], T(&ARRAYR)[SIZE]>
void swap(etl::array_wrapper<T, SIZE, ARRAYL>& lhs,          
          etl::array_wrapper<T, SIZE, ARRAYR>& rhs)

Description
Swaps the array contents of two arrays.

Hash

There is a specialisation for etl::hash for array_wrapper.

Macros

A macro is defined to ease the use of the class.

ETL_ARRAY_WRAPPER(type, array);

Example

// The address of the array MUST be deducible at compile time.  
int cdata = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };  

typedef ETL_ARRAY_WRAPPER(int, cdata) Data;  

// All instances of 'Data' access the SAME array.Data data;  
void Print(Data data)  
{  
    Data::const_iterator itr = data.begin();  
    
    while (itr != data.end())  
    {  
        std::cout << *itr++ << " ";  
    }
}  

Print(data); // Prints "1 2 3 4 5 6 7 8 9 10"  

size_t hashvalue = etl::hash<Data>()(data);  

// Using indexes  
int firstElement = data[Data::FRONT];  

int lastElement = data[Data::BACK];  

// Using forward indexes  
for (int i = Data::BEGIN; i < Data::END; ++i)  
{  
  std::cout << data[i] << " ";  
}

// Using reverse indexes  
for (int i = Data::RBEGIN; i < Data::REND; --i)  
{  
  std::cout << data[i] << " ";  
}