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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 bydest. If the requested substring lasts past the end of the string, or ifcount== npos, the copied substring is[pos, size()).
The resulting character string is not null-terminated.
Contents |
| dest | - | pointer to the destination character string |
| count | - | length of the substring |
| pos | - | position of the first character to include |
Number of characters copied.
std::out_of_range ifpos> size().
If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).
Linear incount.
#include <iostream>#include <string> int main(){std::string foo("WINE"); // brace-initialization initializes all characters to 0,// providing a null-terminatorchar 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:
WIN
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 847 | C++98 | there was no exception safety guarantee | added strong exception safety guarantee |
| returns a substring (public member function)[edit] | |
| copies characters (public member function of std::basic_string_view<CharT,Traits>)[edit] | |
(C++11) | copies a range of elements to a new location (function template)[edit] |
| copies one buffer to another (function)[edit] |
