C++ memset / memcpy / strcpy implementation performance
These are Runtime library functions, not STL (template library) functions.

The run-time library is arguably part of the language (so you can use the built-in library functions and still be "using C++").

It's possible that your compiler is able to generate these as intrinsic functions.

Things you can try to make your functions faster:


Use a compiler with a better optimizer
Copy 4 or 8 bytes at a time
If the buffers aren't aligned on a 4- or 8-byte boundary, copy 1 byte at a time until you come to a boundary alignment, and then copy 4 or 8 bytes at a time