// multiple threads generating musical notes
//
// POSIX version, using locks and conditions
//
#include <stdio.h>
#include <math.h>
#include <pthread.h>
#include <assert.h>
//
// compile flags: -pthread
 
#define Pthread_create(a,b,c,d)	assert(pthread_create(a,b,c,d) == 0)
#define Pthread_mutex_lock(m)	assert(pthread_mutex_lock(m) == 0)
#define Pthread_mutex_unlock(m)	assert(pthread_mutex_unlock(m) == 0)
#define Pthread_cond_signal(c)	assert(pthread_cond_signal(c) == 0)
#define Pthread_cond_wait(c,m)	assert(pthread_cond_wait(c,m) == 0)

#define N 3 // number of threads
 
int notes0[] = { 44, 6, 42, 6, 40, 12, -1 };
int notes1[] = { 47, 2, 52, 4, 52, 2, 51, 2, 49, 2, 51, 2, 52, 4, 47, 2, 47, 4, -1 };
int notes2[] = { 47, 6, 45, 4, 45, 2, 44, 12, -1 };
 
typedef struct
{
  pthread_mutex_t lock;	// lock for wait condition
  pthread_cond_t cond;	// wait condition
 //
  int wait;	// 0 = play() should wait, 1 = main() should wait, -1 = done
  int *notes;	// key, duration pairs, end with -1
  double value;	// output value
}
Data;
 
Data D[N] =
{
  { PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, 1, notes0, 0 },
  { PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, 1, notes1, 0 },
  { PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, 1, notes2, 0 }
};
 
double pi, ratio;
 
void play( int key, int duration, Data *d)
{
  double r, w = (2*pi*440*pow(ratio,key-49))/8000.0;
 
  int n = (duration/10.0)*8000.0;
 
  for( int i = 0; i < n; ++i)
  {
    r = sin(w*i) + 0.5*sin(2*w*i) + 0.25*sin(3*w*i);
    Pthread_mutex_lock( &d->lock);
      while( d->wait == 0) Pthread_cond_wait( &d->cond, &d->lock);
      d->value = r;
      d->wait = 0;
      Pthread_cond_signal( &d->cond);
    Pthread_mutex_unlock( &d->lock);
  }
}

void *f( void *v)
{
  Data *d = v;
 
  for( int i = 0; d->notes[i] >= 0; i += 2) play( d->notes[i], d->notes[i+1], d);
 
  Pthread_mutex_lock( &d->lock);
    while( d->wait == 0) Pthread_cond_wait( &d->cond, &d->lock);
    d->wait = -1; // done
    Pthread_cond_signal( &d->cond);
  Pthread_mutex_unlock( &d->lock);
 
  return 0;
}
 
int main( void)
{
  int done;  double sum;  pthread_t t[N];
 
  pi = 4*atan(1);  ratio = pow(2,1.0/12.0);
 
  for( int i = 0; i < N; ++i) Pthread_create( t+i, 0, f, D+i);
 
  while( 1)
  {
    done = 1; sum = 0;
 
    for( int i = 0; i < N; ++i)
    {
      Pthread_mutex_lock( &D[i].lock);
        while( D[i].wait == 1) Pthread_cond_wait( &D[i].cond, &D[i].lock);
        if( D[i].wait == 0)
        {
	  done = 0; sum += D[i].value; D[i].wait = 1;
	  Pthread_cond_signal( &D[i].cond);
        }
      Pthread_mutex_unlock( &D[i].lock);
    }
 
    if( done) break;
 
    printf( "%g\n", sum);
  }
 
  return 0;
}