etl/docs/strings/string_view.md

title
basic_string_view

{{< callout type="info">}} Header: string_view.h
Similar to:
std::basic_string_view
std::string_view
std::wstring_view
std::u8string_view
std::u16string_view
std::u32string_view {{< /callout >}}

This class implements a view in to a range of a C string, etl::string (+ variants), std::string (+ variants).

Classes

etl::basic_string_view<typename T, typename TTraits = etl::char_traits<T>>

Types

etl::string_view
etl::wstring_view
etl::u8string_view;
etl::u16string_view
etl::u32string_view

Member types

value_type              T
size_type               std::size_t
difference_type         std::ptrdiff_t
reference               value_type&
const_reference         const value_type&
pointer                 value_type*
const_pointer           const value_type*
iterator                Random access iterator
const_iterator          Constant random access iterator
reverse_iterator        std::reverse_iterator<iterator>
const_reverse_iterator  std::reverse_iterator<const_iterator>

Constants

size_t npos

Description
An end of view indicator by the functions that expect a view index.
An error indicator for functions that return a view index.

Constructors

ETL_CONSTEXPR basic_string_view()

Description
Default constructor.

---

ETL_CONSTEXPR basic_string_view(const T* begin, size_t size)

Description
Construct from a start and size.

---

ETL_CONSTEXPR basic_string_view(const T* begin)

Description
Construct from a zero terminated string.

---

ETL_CONSTEXPR basic_string_view(const etl::basic_string_view& other)

Description
Copy constructor.

Modifiers

void remove_prefix(size_t n)

Description
Shrinks the view from the front.
Undefined behaviour if n is larger than the string.

---

void remove_suffix(size_t n)

Description
Shrinks the view from the back.
Undefined behaviour if n is larger than the string.

---

void swap(etl::basic_string_view<T, TTraits>& view)

Description
Swaps with another view.

Element access

const T& at(size_t i) const

Description
Returns a const reference to the indexed element.
Emits an etl::string_view_uninitialised if the view is not initialised.
Emits an etl::string_view_bounds if the index is not in range.
If asserts or exceptions are not enabled then undefined behaviour occurs.

---

const_reference operator[](size_t i) const

Description
Returns a const reference to the indexed element.
Undefined behaviour if the string is empty.

---

const_reference front() const

Description
Returns a const reference to the first element. Undefined behaviour if the string is empty.

---

const_reference back() const

Description
Returns a const reference to the last element. Undefined behaviour if the string is empty.

---

const_pointer data() const

Description
Returns a const pointer to the first element. Undefined behaviour if the string is empty.

Iterators

const_iterator begin() const
const_iterator cbegin() const

Description
Returns an iterator to the beginning of the string view.

---

const_iterator end() const
const_iterator cend() const

Description
Returns an iterator to the end of the string view.

---

const_iterator rbegin() const
const_iterator crbegin() const

Description
Returns a reverse iterator to the beginning of the string view.

---

const_iterator rend() const
const_iterator crend() const

Description
Returns a reverse iterator to the end of the string view.

Operations

size_t copy(T* destination, size_t count, size_t position = 0) const

Description
Copies the sub-string at position for count characters or size() - count, whichever smaller, to the string pointed to by destination.

---

basic_string_view substr(size_t position = 0, size_t count = npos) const

Description
Returns a view which is the sub-string at position for count characters or size() - count, whichever smaller.

Capacity

bool empty() const

Description
Returns true if the size of the string view is zero, otherwise false.

---

size_t size() const

Description
Returns the size of the view.

---

size_t length() const

Description
Alternative for size().

---

size_t max_size() const

Description
Returns the maximum possible size of the view.

Compare

int compare(basic_string_view v) const
int compare(size_t position1, size_t count1, basic_string_view view) const
int compare(size_t position1, size_t count1, 
            basic_string_view view, 
            size_t position2, size_t count2) const
int compare(const T* text) const
int compare(size_t position1, size_t count, const T* text) const
int compare(size_t position1, size_t count1, const T* text, size_t count2) const

Description
Compares two character sequences.

Search

bool starts_with(etl::basic_string_view view) const
bool starts_with(T x) const
bool starts_with(const T* x) const

Description
Checks if the string view begins with the given prefix.

---

bool ends_with(etl::basic_string_view view) const
bool ends_with(T x) const
bool ends_with(const T* x) const

Description
Checks if the string view ends with the given prefix.

---

size_t find(basic_string_view view, size_type position = 0) const
size_t find(T c, size_t position = 0) const
size_t find(const T* text, size_t position, size_t count) const
size_t find(const T* text, size_t position = 0) const;

Description
Finds the first sub-string equal to the given character sequence.

---

size_t rfind(basic_string_view view, size_t position = npos) const
size_t rfind(T c, size_t position = npos) const
size_t rfind(const T* text, size_t position, size_t count) const
size_t rfind(const T* text, size_t position = npos) const

Description
Finds the last sub-string equal to the given character sequence.

---

size_t find_first_of(basic_string_view view, size_t position = 0) const
size_t find_first_of(T c, size_t position = 0) const
size_t find_first_of(const T* text, size_t position, size_t count) const
size_t find_first_of(const T* text, size_t position = 0) const

Description
Finds the first character equal to any of the characters in the given character sequence.

---

size_t find_last_of(basic_string_view view, size_t position = npos) const
size_t find_last_of(T c, size_t position = npos) const
size_t find_last_of(const T* text, size_t position, size_type count) const
size_t find_last_of(const T* text, size_t position = npos) const

Description
Finds the last character equal to any of the characters in the given character sequence.

---

size_t find_first_not_of(basic_string_view view, size_t position = 0) const
size_t find_first_not_of(T c, size_t position = 0) const
size_t find_first_not_of(const T* text, size_t position, size_t count) const
size_t find_first_not_of(const T* text, size_t position = 0) const

Description
Finds the first character not equal to any of the characters in the given character sequence.

---

size_t find_last_not_of(basic_string_view view, size_t position = npos) const
size_t find_last_not_of(T c, size_t position = npos) const
size_t find_last_not_of(const T* text, size_t position, size_t count) const
size_t find_last_not_of(const T* text, size_t position = npos) const

Description
Finds the first character not equal to any of the characters in the given character sequence.

Non-member functions

Lexicographically comparisons

operator ==

Description
true if the contents of the lists are equal, otherwise false.

---

operator !=

Description
true if the contents of the lists are not equal, otherwise false.

---

operator <

Description
true if the contents of the lhs are lexicographically less than the contents of the rhs, otherwise false.

---

operator <=

Description
true if the contents of the lhs are lexicographically less than or equal to the contents of the rhs, otherwise false.

---

operator >

Description
true if the contents of the lhs are lexicographically greater than the contents of the rhs, otherwise false.

---

operator >=

Description
true if the contents of the lhs are lexicographically greater than or equal to the contents of the rhs, otherwise false.

---

void swap(etl::basic_string_view<T, TTraits> lhs,
          etl::basic_string_view<T, TTraits> rhs)

Swaps two views.

Hash

etl::hash<etl::string_view>
etl::hash<etl::wstring_view>
etl::hash<etl::u8string_view>
etl::hash<etl::u16string_view>
etl::hash<etl::u32string_view>

---

Example

etl::string<10> greeting("Hello World");

using View = etl::string_view;

View view(greeting.begin() + 2, greeting.size() - 4);

void Print(const View& view)
{
  std::cout << std::string(view.begin(), view.end());
}

Print(view); // Prints "llo Wo"

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