/* midiroute.c by Matthias Nagorni */#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <alsa/asoundlib.h>#define MAX_MIDI_PORTS   4int open_seq(snd_seq_t **seq_handle, int in_ports[], int out_ports[], int num_in, int num_out);void midi_route(snd_seq_t *seq_handle, int out_ports[], int split_point);/* Open ALSA sequencer wit num_in writeable ports and num_out readable ports. *//* The sequencer handle and the port IDs are returned.                        */  int open_seq(snd_seq_t **seq_handle, int in_ports[], int out_ports[], int num_in, int num_out) {  int l1;  char portname[64];  if (snd_seq_open(seq_handle, "default", SND_SEQ_OPEN_DUPLEX, 0) < 0) {    fprintf(stderr, "Error opening ALSA sequencer.\n");    return(-1);  }  snd_seq_set_client_name(*seq_handle, "MIDI Router");  for (l1 = 0; l1 < num_in; l1++) {    sprintf(portname, "MIDI Router IN %d", l1);    if ((in_ports[l1] = snd_seq_create_simple_port(*seq_handle, portname,              SND_SEQ_PORT_CAP_WRITE|SND_SEQ_PORT_CAP_SUBS_WRITE,              SND_SEQ_PORT_TYPE_APPLICATION)) < 0) {      fprintf(stderr, "Error creating sequencer port.\n");      return(-1);    }  }  for (l1 = 0; l1 < num_out; l1++) {    sprintf(portname, "MIDI Router OUT %d", l1);    if ((out_ports[l1] = snd_seq_create_simple_port(*seq_handle, portname,              SND_SEQ_PORT_CAP_READ|SND_SEQ_PORT_CAP_SUBS_READ,              SND_SEQ_PORT_TYPE_APPLICATION)) < 0) {      fprintf(stderr, "Error creating sequencer port.\n");      return(-1);    }  }  return(0);}/* Read events from writeable port and route them to readable port 0  *//* if NOTEON / OFF event with note < split_point. NOTEON / OFF events *//* with note >= split_point are routed to readable port 1. All other  *//* events are routed to both readable ports.                          */void midi_route(snd_seq_t *seq_handle, int out_ports[], int split_point) {  snd_seq_event_t *ev;  do {    snd_seq_event_input(seq_handle, &ev);    snd_seq_ev_set_subs(ev);      snd_seq_ev_set_direct(ev);    if ((ev->type == SND_SEQ_EVENT_NOTEON)||(ev->type == SND_SEQ_EVENT_NOTEOFF)) {      if (ev->data.note.note < split_point) {        snd_seq_ev_set_source(ev, out_ports[0]);      } else {        snd_seq_ev_set_source(ev, out_ports[1]);      }      snd_seq_event_output_direct(seq_handle, ev);    } else {      snd_seq_ev_set_source(ev, out_ports[0]);      snd_seq_event_output_direct(seq_handle, ev);      snd_seq_ev_set_source(ev, out_ports[1]);      snd_seq_event_output_direct(seq_handle, ev);    }    snd_seq_free_event(ev);  } while (snd_seq_event_input_pending(seq_handle, 0) > 0);}int main(int argc, char *argv[]) {  snd_seq_t *seq_handle;  int in_ports[MAX_MIDI_PORTS], out_ports[MAX_MIDI_PORTS];  int npfd, split_point;  struct pollfd *pfd;    if (argc < 2) {    fprintf(stderr, "\nmidiroute <split_point>\n\n");    exit(1);  } else {    split_point = atoi(argv[1]);    }    if (open_seq(&seq_handle, in_ports, out_ports, 1, 2) < 0) {    fprintf(stderr, "ALSA Error.\n");    exit(1);  }  npfd = snd_seq_poll_descriptors_count(seq_handle, POLLIN);  pfd = (struct pollfd *)alloca(npfd * sizeof(struct pollfd));  snd_seq_poll_descriptors(seq_handle, pfd, npfd, POLLIN);  while (1) {    if (poll(pfd, npfd, 100000) > 0) {      midi_route(seq_handle, out_ports, split_point);    }    }}