+/* return the last timer interval (ms) */
+btime_t DEVICE::get_timer_count()
+{
+ btime_t old = last_timer;
+ last_timer = get_current_btime();
+ return last_timer - old;
+}
+
+/* read from fd */
+ssize_t DEVICE::read(void *buf, size_t len)
+{
+ ssize_t read_len ;
+
+ get_timer_count();
+
+ if (this->is_tape()) {
+ read_len = tape_read(fd, buf, len);
+ } else {
+ read_len = ::read(fd, buf, len);
+ }
+
+ last_tick = get_timer_count();
+
+ DevReadTime += last_tick;
+ VolCatInfo.VolReadTime += last_tick;
+
+ if (read_len > 0) { /* skip error */
+ DevReadBytes += read_len;
+ }
+
+ return read_len;
+}
+
+/* write to fd */
+ssize_t DEVICE::write(const void *buf, size_t len)
+{
+ ssize_t write_len ;
+
+ get_timer_count();
+
+ if (this->is_tape()) {
+ write_len = tape_write(fd, buf, len);
+ } else {
+ write_len = ::write(fd, buf, len);
+ }
+
+ last_tick = get_timer_count();
+
+ DevWriteTime += last_tick;
+ VolCatInfo.VolWriteTime += last_tick;
+
+ if (write_len > 0) { /* skip error */
+ DevWriteBytes += write_len;
+ }
+
+ return write_len;
+}