#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#define BUFFER "./buffer"

/*
        This declaration is *MISSING* in many Solaris environments.
        It should be in the <sys/sem.h> file but often is not!  If you
	receive a duplicate definition error message for semun then 
	comment out the union declaration.
union semun {
  int             val;
  struct semid_ds *buf;
  ushort         *array;
};
*/
main(int argc, char *argv[ ]) {

  FILE           *fptr;
  static struct sembuf
                  acquire = {0, -1, SEM_UNDO},
                  release = {0,  1, SEM_UNDO};
  pid_t           c_pid;
  key_t           ipc_key;
  static ushort   start_val[2] = {1, 0};
  int             semid, i, producer = 0, n, p_sleep, c_sleep;
  union semun     arg;
  enum { READ, MADE };

  if (argc != 2) {
    fprintf(stderr, "%s sleep_time \n", argv[0]);
    exit(-1);
  }
  ipc_key = ftok(".", 'S');

  if ((semid = semget(ipc_key, 2, IPC_CREAT | IPC_EXCL | 0666)) != -1) {
    producer = 1;
    arg.array = start_val;
    if (semctl(semid, 0, SETALL, arg) == -1) {
      perror("semctl -- producer -- initialization");
      exit(1);
    }
  } else if ((semid = semget(ipc_key, 2, 0)) == -1) {
    perror("semget -- consumer -- obtaining semaphore");
    exit(2);
  }
  switch (producer) {
  case 1:			/* the PRODUCER */
    p_sleep = atoi(argv[1]);
    srand((unsigned) getpid());
    for (i = 0; i < 10; i++) {
      sleep(p_sleep);
      n = rand() % 99 + 1;
      printf("A. The number [%2d] generated by producer\n", n);
      acquire.sem_num = READ;
      if (semop(semid, &acquire, 1) == -1) {
	perror("semop -- producer -- waiting for consumer to read number");
	exit(3);
      }
      if ( (fptr = fopen(BUFFER, "w")) == NULL ){
       perror(BUFFER);
       exit(4);
      }
      fprintf(fptr, "%d\n", n);
      fclose(fptr);
      release.sem_num = MADE;
      printf("B. The number [%2d] deposited by producer\n", n);
      if (semop(semid, &release, 1) == -1) {
	perror("semop -- producer -- indicating new number has been made");
	exit(5);
      }
    }
    sleep(5);
    if (semctl(semid, 0, IPC_RMID, (struct msquid_ds *) 0) == -1) {
      perror("semctl:producer");
      exit(6);
    }
    unlink(BUFFER);
    break;
  case 0:			/* the CONSUMER */
    c_sleep = atoi(argv[1]);
    c_pid = getpid();
    while (1) {
      sleep(c_sleep);
      acquire.sem_num = MADE;
      if (semop(semid, &acquire, 1) == -1) {
	perror("semop -- consumer -- waiting for new number to be made");
	exit(7);
      }
      if ( (fptr = fopen(BUFFER, "r")) == NULL ){
        perror( BUFFER );
        exit(8);
      }
      fscanf(fptr, "%d", &n);
      fclose(fptr);
      release.sem_num = READ;
      if (semop(semid, &release, 1) == -1) {
	perror("semop -- consumer -- indicating number has been read");
	exit(9);
      }
      printf("C. The number [%2d] obtained  by consumer %6d\n", n, c_pid);
    }
  }
 exit(0);
}