- if (s->track_filepos && (pos != 0 || s->last_internal_pos != 0)) {
- if (s->last_internal_pos == 0) {
- s->total_bytes_read = pos;
- } else {
- off_t pos_movement = pos - s->last_caller_pos; /* Can be < 0. */
-
- if (pos_movement == 0) {
- pos = s->last_internal_pos;
- } else {
- /* The current file stream position differs from the
- last one, so caller must have called ftell/o().
- Or, this is the first call and the file position
- was not at 0. */
-
- if (s->readpos + pos_movement >= s->msg_buf &&
- s->readpos + pos_movement < s->end) {
- /* This is currently unused. It could be used by
- parse_mime() if it was changed to use a global
- m_getfld_state. */
- /* We can shift readpos and remain within the
- bounds of msg_buf. */
- s->readpos += pos_movement;
- s->total_bytes_read += pos_movement;
- pos = s->last_internal_pos;
- } else {
- size_t num_read;
-
- /* This seek skips past an integral number of
- chunks of size MSG_INPUT_SIZE. */
- fseeko (iob, pos/MSG_INPUT_SIZE * MSG_INPUT_SIZE, SEEK_SET);
- num_read = fread (s->msg_buf, 1, MSG_INPUT_SIZE, iob);
- s->readpos = s->msg_buf + pos % MSG_INPUT_SIZE;
- s->end = s->msg_buf + num_read;
- s->total_bytes_read = pos;
- }
- }