//This model corresponds to the solution to the bounded-buffer
//Producer/Consumer Problem Using Semaphores discussed by Stallings
//in Figure 5.13 (Operating Systems, Fifth edition).
//Basically the same solution also is presented in Figure 2-12
//of Tanenbaum & Woodhull (Operating Systems, Second edition)
//Model constructed by Frits Vaandrager on 15/3/06
//Ideas from Martijn Hendriks, Koen Vermeer, Justus Freijzer, and Bart Kerkhoff
//have been used in this model.
const int sizeofbuffer=1000;
const int M = 3; //Number of semaphores
const int N = 2; //Number of processes
//Names of semaphores
const int s = 0;
const int n = 1;
const int e = 2;
//Names of processes
const int producer = 0;
const int consumer = 1;
chan semWait[M][N];
chan semSignal[M][N];
chan semGo[M][N];
int buffer = 0;
Consumer
void take(){buffer--;}
void consume(){}csProducer//Insert local declarations of clocks, variables and constants.
void produce(){}
void append(){buffer++;}
csSemaphoreconst int id, const int queue_size, const int init_val//The value of the semaphore
int count = init_val;
//The queue of the semaphore
//value -1 denotes an empty array entry
int[-1,N-1] queue[queue_size];
//An auxiliary variable used to temporarily store process id
meta int[0,N-1] q;
void initialize ()
{
for (i : int[0,queue_size-1])
{queue[i] = -1;}
}
void deQueue ()
{
for (i : int[1,queue_size-1])
queue[i-1] = queue[i];
queue[queue_size-1] = -1;
}
void enQueue (int p)
{
int i = 0;
while (queue[i]>=0){i++;};
queue[i]=p;
}
int[0,N-1] headQueue ( )
{
return queue[0];
}
bool fullQueue ( )
{
for (i : int[0,queue_size-1])
{
if (queue[i]==-1) {return false;}
}
return true;
}overflow//Insert process assignments.
//Semaphore s controls access to the critical section
Sem_s = Semaphore(s,1,1);
//Semaphore n (when nonnegative) counts the number of full buffer slots
Sem_n = Semaphore(n,1,0);
//Semaphore e counts the number of empty buffer slots
Sem_e = Semaphore(e,1,sizeofbuffer);
//Edit system definition.
system Consumer,Producer,Sem_s,Sem_n,Sem_e;