std::basic_string_view<CharT,Traits>::copy

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string_view

Member functions basic_string_view::basic_string_view    basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap

Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::contains (C++23) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view> (C++20) Deduction guides(C++20)

 

size_type copy( CharT* dest, size_type count, size_type pos = 0 ) const;		(since C++17) (until C++20)
constexpr size_type copy( CharT* dest, size_type count,                           size_type pos = 0 ) const;		(since C++20)

Copies the substring [pos, pos + rcount) to the character array pointed to by dest, where rcount is the smaller of count and size() - pos.

Equivalent to Traits::copy(dest, data() + pos, rcount).

Parameters

dest	-	pointer to the destination character string
count	-	requested substring length
pos	-	position of the first character

Return value

Number of characters copied

Exceptions

std::out_of_range if pos > size().

Complexity

Linear in rcount.

Example

Run this code

#include <array>
#include <cstddef>
#include <iostream>
#include <stdexcept>
#include <string_view>
 
int main()
{
    constexpr std::basic_string_view<char> source{"ABCDEF"};
    std::array<char, 8> dest;
    std::size_t count{}, pos{};
 
    dest.fill('\0');
    source.copy(dest.data(), count = 4); // pos = 0
    std::cout << dest.data() << '\n'; // ABCD
 
    dest.fill('\0');
    source.copy(dest.data(), count = 4, pos = 1);
    std::cout << dest.data() << '\n'; // BCDE
 
    dest.fill('\0');
    source.copy(dest.data(), count = 42, pos = 2); // ok, count -> 4
    std::cout << dest.data() << '\n'; // CDEF
 
    try
    {
        source.copy(dest.data(), count = 1, pos = 666); // throws: pos > size()
    }
    catch(std::out_of_range const& ex)
    {
        std::cout << ex.what() << '\n';
    }
}

Output:

ABCD
BCDE
CDEF
basic_string_view::copy: __pos (which is 666) > __size (which is 6)

See also

substr (C++17)	returns a substring (public member function)
copy	copies characters (public member function of std::basic_string<CharT,Traits,Allocator>)
copycopy_if (C++11)	copies a range of elements to a new location (function template)
memcpy	copies one buffer to another (function)