Function sbuf_printf_drain

freebsd/kern/subr_prf.c:1273–1310

#endif

int
sbuf_printf_drain(void *arg, const char *data, int len)
{
	size_t *retvalptr;
	int r;
#ifdef _KERNEL
	char *dataptr;
	char oldchr;

	/*
	 * This is allowed as an extra byte is always resvered for
	 * terminating NUL byte.  Save and restore the byte because
	 * we might be flushing a record, and there may be valid
	 * data after the buffer.
	 */
	oldchr = data[len];
	dataptr = __DECONST(char *, data);
	dataptr[len] = '\0';

	prf_putbuf(dataptr, TOLOG | TOCONS, -1);
	r = len;

	dataptr[len] = oldchr;

#else /* !_KERNEL */

	r = printf("%.*s", len, data);
	if (r < 0)
		return (-errno);

#endif

	retvalptr = arg;
	if (retvalptr != NULL)
		*retvalptr += r;

	return (r);
}