Hola challenge

#include <stdio.h>
#include <conio.h>
#include <memory.h>
#include <string.h>
#include <malloc.h>

void str_cpy(char **const _ppDest, char const *const _psSource)
{
    int nSourceSize = -1, nSize = 0;
    while (_psSource[++nSourceSize]) {};
    if (*_ppDest)
        nSize = _msize(*_ppDest);
    if (nSize < nSourceSize + 1)
        *_ppDest = new char[nSourceSize + 1];
    memcpy(*_ppDest, _psSource, nSourceSize + 1);
}

void str_cat(char **const _ppDest, char const *const _psSource)
{
    int nSourceSize = -1, nSize = 0, nDestSize = -1;
    while (_psSource[++nSourceSize]) {}; while ((*_ppDest)[++nDestSize]) {};
    if (*_ppDest)
        nSize = _msize(*_ppDest);
    if (nSize < nDestSize + nSourceSize)
        *_ppDest = new char[nDestSize + nSourceSize + 1];
    memcpy(*_ppDest + nDestSize, _psSource, nSourceSize + 1);
}

int main()
{
    char *s = nullptr;

    str_cpy(&s, "Hola Hola");
    str_cpy(&s, s + 5);
    str_cat(&s, " World");

    printf("%s!\n", s);

    _getch();
    return 0;
}