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406 lines
9.0 KiB
Markdown
406 lines
9.0 KiB
Markdown
---
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title: "basic_string_view"
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---
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{{< callout type="info">}}
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Header: `string_view.h`
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Similar to:
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`std::basic_string_view`
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`std::string_view`
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`std::wstring_view`
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`std::u8string_view`
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`std::u16string_view`
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`std::u32string_view`
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{{< /callout >}}
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This class implements a view in to a range of a `C` string, `etl::string` (+ variants), `std::string` (+ variants).
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## Classes
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```cpp
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etl::basic_string_view<typename T, typename TTraits = etl::char_traits<T>>
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```
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## Types
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```cpp
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etl::string_view
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etl::wstring_view
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etl::u8string_view;
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etl::u16string_view
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etl::u32string_view
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```
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## Member types
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```cpp
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value_type T
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size_type std::size_t
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difference_type std::ptrdiff_t
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reference value_type&
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const_reference const value_type&
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pointer value_type*
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const_pointer const value_type*
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iterator Random access iterator
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const_iterator Constant random access iterator
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reverse_iterator std::reverse_iterator<iterator>
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const_reverse_iterator std::reverse_iterator<const_iterator>
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```
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## Constants
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```cpp
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size_t npos
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```
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**Description**
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An end of view indicator by the functions that expect a view index.
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An error indicator for functions that return a view index.
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## Constructors
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```cpp
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ETL_CONSTEXPR basic_string_view()
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```
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**Description**
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Default constructor.
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---
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```cpp
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ETL_CONSTEXPR basic_string_view(const T* begin, size_t size)
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```
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**Description**
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Construct from a start and size.
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---
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```cpp
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ETL_CONSTEXPR basic_string_view(const T* begin)
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```
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**Description**
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Construct from a zero terminated string.
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---
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```cpp
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ETL_CONSTEXPR basic_string_view(const etl::basic_string_view& other)
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```
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**Description**
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Copy constructor.
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## Modifiers
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```cpp
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void remove_prefix(size_t n)
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```
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**Description**
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Shrinks the view from the front.
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Undefined behaviour if n is larger than the string.
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---
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```cpp
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void remove_suffix(size_t n)
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```
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**Description**
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Shrinks the view from the back.
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Undefined behaviour if n is larger than the string.
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---
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```cpp
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void swap(etl::basic_string_view<T, TTraits>& view)
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```
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**Description**
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Swaps with another view.
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## Element access
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```cpp
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const T& at(size_t i) const
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```
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**Description**
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Returns a const reference to the indexed element.
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Emits an `etl::string_view_uninitialised` if the view is not initialised.
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Emits an `etl::string_view_bounds` if the index is not in range.
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If asserts or exceptions are not enabled then undefined behaviour occurs.
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---
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```cpp
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const_reference operator[](size_t i) const
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```
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**Description**
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Returns a const reference to the indexed element.
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Undefined behaviour if the string is empty.
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---
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```cpp
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const_reference front() const
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```
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**Description**
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Returns a const reference to the first element.
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Undefined behaviour if the string is empty.
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---
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```cpp
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const_reference back() const
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```
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**Description**
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Returns a const reference to the last element.
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Undefined behaviour if the string is empty.
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---
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```cpp
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const_pointer data() const
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```
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**Description**
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Returns a const pointer to the first element.
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Undefined behaviour if the string is empty.
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## Iterators
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```cpp
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const_iterator begin() const
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const_iterator cbegin() const
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```
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**Description**
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Returns an iterator to the beginning of the string view.
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---
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```cpp
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const_iterator end() const
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const_iterator cend() const
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```
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**Description**
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Returns an iterator to the end of the string view.
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---
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```cpp
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const_iterator rbegin() const
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const_iterator crbegin() const
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```
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**Description**
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Returns a reverse iterator to the beginning of the string view.
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---
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```cpp
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const_iterator rend() const
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const_iterator crend() const
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```
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**Description**
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Returns a reverse iterator to the end of the string view.
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## Operations
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```cpp
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size_t copy(T* destination, size_t count, size_t position = 0) const
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```
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**Description**
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Copies the sub-string at position for count characters or size() - count, whichever smaller, to the string pointed to by destination.
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---
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```cpp
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basic_string_view substr(size_t position = 0, size_t count = npos) const
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```
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**Description**
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Returns a view which is the sub-string at position for count characters or size() - count, whichever smaller.
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## Capacity
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```cpp
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bool empty() const
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```
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**Description**
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Returns true if the size of the string view is zero, otherwise false.
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---
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```cpp
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size_t size() const
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```
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**Description**
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Returns the size of the view.
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---
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```cpp
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size_t length() const
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```
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**Description**
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Alternative for size().
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---
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```cpp
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size_t max_size() const
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```
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**Description**
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Returns the maximum possible size of the view.
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## Compare
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```cpp
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int compare(basic_string_view v) const
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int compare(size_t position1, size_t count1, basic_string_view view) const
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int compare(size_t position1, size_t count1,
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basic_string_view view,
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size_t position2, size_t count2) const
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int compare(const T* text) const
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int compare(size_t position1, size_t count, const T* text) const
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int compare(size_t position1, size_t count1, const T* text, size_t count2) const
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```
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**Description**
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Compares two character sequences.
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## Search
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```cpp
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bool starts_with(etl::basic_string_view view) const
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bool starts_with(T x) const
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bool starts_with(const T* x) const
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```
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**Description**
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Checks if the string view begins with the given prefix.
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---
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```cpp
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bool ends_with(etl::basic_string_view view) const
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bool ends_with(T x) const
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bool ends_with(const T* x) const
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```
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**Description**
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Checks if the string view ends with the given prefix.
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---
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```cpp
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size_t find(basic_string_view view, size_type position = 0) const
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size_t find(T c, size_t position = 0) const
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size_t find(const T* text, size_t position, size_t count) const
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size_t find(const T* text, size_t position = 0) const;
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```
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**Description**
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Finds the first sub-string equal to the given character sequence.
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---
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```cpp
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size_t rfind(basic_string_view view, size_t position = npos) const
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size_t rfind(T c, size_t position = npos) const
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size_t rfind(const T* text, size_t position, size_t count) const
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size_t rfind(const T* text, size_t position = npos) const
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```
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**Description**
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Finds the last sub-string equal to the given character sequence.
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---
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```cpp
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size_t find_first_of(basic_string_view view, size_t position = 0) const
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size_t find_first_of(T c, size_t position = 0) const
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size_t find_first_of(const T* text, size_t position, size_t count) const
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size_t find_first_of(const T* text, size_t position = 0) const
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```
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**Description**
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Finds the first character equal to any of the characters in the given character sequence.
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---
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```cpp
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size_t find_last_of(basic_string_view view, size_t position = npos) const
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size_t find_last_of(T c, size_t position = npos) const
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size_t find_last_of(const T* text, size_t position, size_type count) const
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size_t find_last_of(const T* text, size_t position = npos) const
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```
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**Description**
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Finds the last character equal to any of the characters in the given character sequence.
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---
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```cpp
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size_t find_first_not_of(basic_string_view view, size_t position = 0) const
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size_t find_first_not_of(T c, size_t position = 0) const
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size_t find_first_not_of(const T* text, size_t position, size_t count) const
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size_t find_first_not_of(const T* text, size_t position = 0) const
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```
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**Description**
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Finds the first character not equal to any of the characters in the given character sequence.
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---
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```cpp
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size_t find_last_not_of(basic_string_view view, size_t position = npos) const
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size_t find_last_not_of(T c, size_t position = npos) const
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size_t find_last_not_of(const T* text, size_t position, size_t count) const
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size_t find_last_not_of(const T* text, size_t position = npos) const
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```
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**Description**
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Finds the first character not equal to any of the characters in the given character sequence.
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## Non-member functions
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**Lexicographically comparisons**
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`==` `true` if the contents of the string views are equal,
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otherwise `false`.
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`!=` `true` if the contents of the string views are not equal,
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otherwise `false`.
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`< ` `true` if the contents of the lhs are lexicographically less than the contents of the rhs,
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otherwise `false`.
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`<=` `true` if the contents of the lhs are lexicographically less than or equal to the contents of the rhs,
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otherwise `false`.
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`> ` `true` if the contents of the lhs are lexicographically greater than the contents of the rhs,
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otherwise `false`.
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`>=` `true` if the contents of the lhs are lexicographically greater than or equal to the contents of the rhs,
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otherwise `false`.
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---
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```cpp
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void swap(etl::basic_string_view<T, TTraits> lhs,
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etl::basic_string_view<T, TTraits> rhs)
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```
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Swaps two views.
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## Hash
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```cpp
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etl::hash<etl::string_view>
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etl::hash<etl::wstring_view>
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etl::hash<etl::u8string_view>
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etl::hash<etl::u16string_view>
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etl::hash<etl::u32string_view>
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---
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**Example**
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```cpp
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etl::string<10> greeting("Hello World");
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using View = etl::string_view;
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View view(greeting.begin() + 2, greeting.size() - 4);
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void Print(const View& view)
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{
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std::cout << std::string(view.begin(), view.end());
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}
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Print(view); // Prints "llo Wo"
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size_t hashvalue = etl::hash<View>()(view);
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```
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