zircon/system/uapp/midiecho/midiecho.c

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <dirent.h>
#include <fcntl.h>
#include <fuchsia/hardware/midi/c/fidl.h>
#include <lib/fdio/unsafe.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <zircon/types.h>

#define DEV_MIDI "/dev/class/midi"

static bool open_devices(int* out_src_fd, int* out_dest_fd) {
  int src_fd = -1;
  int dest_fd = -1;

  struct dirent* de;
  DIR* dir = opendir(DEV_MIDI);
  if (!dir) {
    printf("Error opening %s\n", DEV_MIDI);
    return -1;
  }

  while ((de = readdir(dir)) != NULL && (src_fd == -1 || dest_fd == -1)) {
    char devname[128];

    snprintf(devname, sizeof(devname), "%s/%s", DEV_MIDI, de->d_name);
    int fd = open(devname, O_RDWR);
    if (fd < 0) {
      printf("Error opening %s\n", devname);
      continue;
    }

    fuchsia_hardware_midi_Info device_info;
    fdio_t* fdio = fdio_unsafe_fd_to_io(fd);
    zx_status_t status =
        fuchsia_hardware_midi_DeviceGetInfo(fdio_unsafe_borrow_channel(fdio), &device_info);
    fdio_unsafe_release(fdio);
    if (status != ZX_OK) {
      printf("fuchsia.hardware.midi.Device/GetInfo failed for %s\n", devname);
      close(fd);
      continue;
    }
    if (device_info.is_source) {
      if (src_fd == -1) {
        src_fd = fd;
      } else {
        close(fd);
      }
    } else if (device_info.is_sink) {
      if (dest_fd == -1) {
        dest_fd = fd;
      } else {
        close(fd);
      }
    } else {
      close(fd);
    }
  }

  closedir(dir);
  if (src_fd == -1) {
    close(dest_fd);
    return false;
  }
  if (dest_fd == -1) {
    close(src_fd);
    return false;
  }

  *out_src_fd = src_fd;
  *out_dest_fd = dest_fd;
  return true;
}

int main(int argc, char** argv) {
  int src_fd = -1, dest_fd = -1;
  if (!open_devices(&src_fd, &dest_fd)) {
    printf("couldn't find a usable MIDI source and sink\n");
    return -1;
  }

  while (1) {
    uint8_t buffer[3];

    int length = read(src_fd, buffer, sizeof(buffer));
    if (length < 0)
      break;
    printf("MIDI event:");
    for (int i = 0; i < length; i++) {
      printf(" %02X", buffer[i]);
    }
    printf("\n");
    if (write(dest_fd, buffer, length) < 0)
      break;
  }

  close(src_fd);
  close(dest_fd);

  return 0;
}