linux pcspkr rickroll in C

rickroll.c

/* compile:
```
gcc rickroll.c
sudo ./a.out
```
MUST BE RUN AS ROOT
*/
#include <fcntl.h>       // open
#include <linux/input.h> // struct input_event
#include <linux/kd.h>
#include <math.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <time.h>   // nanosleep
#include <unistd.h> // write, close
#include <unistd.h>
/*
    https://create.arduino.cc/projecthub/410027/rickroll-piezo-buzzer-a1cd11
    modified for a standard pc
*/
static char const *const default_device = "/dev/console";

#define a3f 208 // 208 Hz
#define b3f 233 // 233 Hz
#define b3 247  // 247 Hz
#define c4 261  // 261 Hz MIDDLE C
#define c4s 277 // 277 Hz
#define e4f 311 // 311 Hz
#define f4 349  // 349 Hz
#define a4f 415 // 415 Hz
#define b4f 466 // 466 Hz
#define b4 493  // 493 Hz
#define c5 523  // 523 Hz
#define c5s 554 // 554 Hz
#define e5f 622 // 622 Hz
#define f5 698  // 698 Hz
#define f5s 740 // 740 Hz
#define a5f 831 // 831 Hz

#define rest -1

#define CLOCK_TICK_RATE 1193180
volatile int beatlength = 100; // determines tempo
float beatseparationconstant = 0.3;

int threshold;

int a; // part index
int b; // song index
int c; // lyric index

bool flag;

// Parts 1 and 2 (Intro)

int song1_intro_melody[] = {c5s, e5f, e5f, f5,   a5f, f5s, f5,
                            e5f, c5s, e5f, rest, a4f, a4f};

int song1_intro_rhythmn[] = {6, 10, 6, 6, 1, 1, 1, 1, 6, 10, 4, 2, 10};

// Parts 3 or 5 (Verse 1)

int song1_verse1_melody[] = {
    rest, c4s,  c4s,  c4s, c4s, e4f, rest, c4,   b3f, a3f, rest, b3f, b3f,
    c4,   c4s,  a3f,  a4f, a4f, e4f, rest, b3f,  b3f, c4,  c4s,  b3f, c4s,
    e4f,  rest, c4,   b3f, b3f, a3f, rest, b3f,  b3f, c4,  c4s,  a3f, a3f,
    e4f,  e4f,  e4f,  f4,  e4f, c4s, e4f,  f4,   c4s, e4f, e4f,  e4f, f4,
    e4f,  a3f,  rest, b3f, c4,  c4s, a3f,  rest, e4f, f4,  e4f};

int song1_verse1_rhythmn[] = {2, 1, 1, 1, 1, 2, 1, 1, 1, 5, 1, 1, 1, 1, 3, 1,
                              2, 1, 5, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3,
                              1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 4, 5, 1, 1, 1,
                              1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 3, 1, 1, 1, 3};

// Parts 4 or 6 (Chorus)

int song1_chorus_melody[] = {
    b4f, b4f, a4f, a4f, f5,  f5,  e5f, b4f, b4f, a4f,  a4f, e5f, e5f, c5s, c5,
    b4f, c5s, c5s, c5s, c5s, c5s, e5f, c5,  b4f, a4f,  a4f, a4f, e5f, c5s, b4f,
    b4f, a4f, a4f, f5,  f5,  e5f, b4f, b4f, a4f, a4f,  a5f, c5,  c5s, c5,  b4f,
    c5s, c5s, c5s, c5s, c5s, e5f, c5,  b4f, a4f, rest, a4f, e5f, c5s, rest};

int song1_chorus_rhythmn[] = {1, 1, 1, 1, 3, 3, 6, 1, 1, 1, 1, 3, 3, 3, 1,
                              2, 1, 1, 1, 1, 3, 3, 3, 1, 2, 2, 2, 4, 8, 1,
                              1, 1, 1, 3, 3, 6, 1, 1, 1, 1, 3, 3, 3, 1, 2,
                              1, 1, 1, 1, 3, 3, 3, 1, 2, 2, 2, 4, 8, 4};

void delay(unsigned int ms) {
  struct timespec duration = {.tv_sec = ms / 1000U,
                              .tv_nsec = (long)(ms % 1000UL * 1000UL * 1000UL)};
  nanosleep(&duration, NULL);
}

void start_beep(int fd, int freq) {
  if (freq == 0) {
    ioctl(fd, KIOCSOUND, 0);
  } else {
    ioctl(fd, KIOCSOUND, (int)(CLOCK_TICK_RATE / freq));
  }
}

void tone(int fd, int freq, int duration) {
  start_beep(fd, freq);
  delay(duration);
  start_beep(fd, 0);
}

void play(int piezo) {
  int notelength;
  if (a == 1 || a == 2) {
    // intro
    notelength = beatlength * song1_intro_rhythmn[b];
    if (song1_intro_melody[b] > 0) {
      tone(piezo, song1_intro_melody[b], notelength);
    }
    b++;
    if (b >= sizeof(song1_intro_melody) / sizeof(int)) {
      a++;
      b = 0;
      c = 0;
    }
  } else if (a == 3 || a == 5) {
    // verse
    notelength = beatlength * 2 * song1_verse1_rhythmn[b];
    if (song1_verse1_melody[b] > 0) {
      tone(piezo, song1_verse1_melody[b], notelength);
      c++;
    }
    b++;
    if (b >= sizeof(song1_verse1_melody) / sizeof(int)) {
      a++;
      b = 0;
      c = 0;
    }
  } else if (a == 4 || a == 6) {
    // chorus
    notelength = beatlength * song1_chorus_rhythmn[b];
    if (song1_chorus_melody[b] > 0) {
      tone(piezo, song1_chorus_melody[b], notelength);
      c++;
    }
    b++;
    if (b >= sizeof(song1_chorus_melody) / sizeof(int)) {
      a++;
      b = 0;
      c = 0;
    }
  }
  delay(notelength);
  delay(notelength * beatseparationconstant);
  if (a == 7) { // loop back around to beginning of song
    a = 1;
  }
}

int main() {

  int fd = open(default_device, O_WRONLY);

  flag = true;
  a = 4;
  b = 0;
  c = 0;
  while (true) {
    if (flag == true) {
      play(fd);
    }
  }
  close(fd);
  return 0;
}