source: CIVL/examples/concurrency/boundedBuffer.cvl

/* boundedBuffer.cvl:
 * This program impelments a bounded-buffer.
 * It describes two processes, the producer and consumer, 
 * which share a common, fixed-size buffer
 * used as a queue. 
 *
 * The producer's job is to generate a piece of data, 
 * put it into the buffer and start again. 
 * At the same time, the consumer is consuming the data 
 * (i.e., removing it from the buffer) one piece at a time. *
 * The problem is to make sure that the producer won't try 
 * to add data into the buffer if it's full and that the 
 * consumer won't try to remove data from an empty buffer.
 *
 * This program is correct only when the number of producer and
 * the number of consumer are exactly one, respectively.
 */
#include<civlc.cvh>

#define NPRODUCER 1
#define NCONSUMER 1

$input int BUFFER_SIZE = 50;
int fillCount = 0;
int emptyCount = BUFFER_SIZE;
 
void producer() {
  while ($true) {
    // produce item
    $when (emptyCount > 0);
    $assert(emptyCount > 0);
    emptyCount--;
    // put item into buffer
    fillCount++;
  }
}
 
void consumer() {
  while ($true) {
    $when (fillCount > 0);
    $assert(fillCount > 0);
    fillCount--;
    // remove item from buffer
    emptyCount++;
    // consume item
  }
}

void main(){
  $proc producers[NPRODUCER];
  $proc consumers[NCONSUMER];

  for (int i = 0; i < NCONSUMER; i++)
    consumers[i] = $spawn consumer();
  for (int i = 0; i < NPRODUCER; i++)
    producers[i] = $spawn producer();
  $waitall(consumers, NCONSUMER);
  $waitall(producers, NPRODUCER);
}