NAME¶

std::basic_string_view::copy - std::basic_string_view::copy

Synopsis¶

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

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