std::basic_string<CharT,Traits,Allocator>::copy - cppreference.com (original) (raw)

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

Copies a substring [pos, pos + count) to character string pointed to by dest. If the requested substring lasts past the end of the string, or if count == npos, the copied substring is [pos, size()).

The resulting character string is not null-terminated.

Contents

• 1 Parameters
• 2 Return value
• 3 Exceptions
• 4 Complexity
• 5 Example
• 6 Defect reports
• 7 See also

[edit] Parameters

[edit] Return value

Number of characters copied.

[edit] Exceptions

std::out_of_range if pos > size().

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

[edit] Complexity

Linear in count.

[edit] Example

#include #include   int main() { std::string foo("WINE");   // brace-initialization initializes all characters to 0, // providing a null-terminator char bar[4]{};   // do not copy the last char, to guarantee null-termination foo.copy(bar, sizeof bar - 1);   std::cout << bar << '\n'; // requires bar to be null-terminated }

Output:

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also

| | returns a substring (public member function) [edit] | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | copies characters (public member function of std::basic_string_view<CharT,Traits>) [edit] | | | copies a range of elements to a new location (function template) [edit] | | | copies one buffer to another (function) [edit] |