strspy函数实现

char * strcpy_to (char *dst, const char *src)
{
    char *address = dst;
    assert((dst != NULL) && (src != NULL));

    while(*src)   
    {
       *dst++ = *src++;
    }
    *dst = ‘\0‘;
    
    return address;
} 

char * strcpy_to(char *dst, const char *src)
{
    char *ret = dst;

    assert(dst != NULL && src != NULL);
    my_memcpy(dst, src, strlen(src)+1);

    return ret;
}

char * my_memcpy(char *dst, const char *src, int cnt)
{
    assert(dst != NULL && src != NULL);
    char *ret = dst;

    if (dst >= src && dst <= (src+cnt-1))
    {
        dst = dst+cnt-1;
        src = src+cnt-1;

        while (cnt--)
            *dst-- = *src--;
    }
    else
    {
        while (cnt--)
            *dst++ = *src++;
    }


    return ret;
}