static void wipe_buf(pj_str_t *buf)
{
    volatile char *p = buf->ptr;
    pj_ssize_t len = buf->slen;
    while (len--) *p++ = 0;
    buf->slen = 0;
}
static void wipe_buf(pj_str_t *buf)
{
    volatile char *p = buf->ptr;
    pj_ssize_t len = buf->slen;
    while (len--) *p++ = 0;
    buf->slen = 0;
}