feat: update structure

cs2106/labs/lab3/progs/part2/barrier.c

@@ -0,0 +1,55 @@
+#include <semaphore.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/shm.h>
+
+int nproc = 0;
+// count must be a semaphore
+int *count;
+sem_t *barrier;
+sem_t *countMut;
+int barrierShmId, countShmId, countMutShmId;
+
+void init_barrier(int numproc) {
+  nproc = numproc;
+  barrierShmId = shmget(IPC_PRIVATE, sizeof(sem_t), IPC_CREAT | 0600);
+  countMutShmId = shmget(IPC_PRIVATE, sizeof(sem_t), IPC_CREAT | 0600);
+
+  countShmId = shmget(IPC_PRIVATE, sizeof(int), IPC_CREAT | 0600);
+
+  barrier = (sem_t *)shmat(barrierShmId, NULL, 0);
+  countMut = (sem_t *)shmat(countMutShmId, NULL, 0);
+
+  count = (int *)shmat(countShmId, NULL, 0);
+  sem_init(barrier, 1, 0);
+  sem_init(countMut, 1, 1);
+}
+
+void reach_barrier() {
+  sem_wait(countMut);
+  *count += 1;
+  sem_post(countMut);
+  if (*count == nproc) {
+    sem_post(barrier);
+  } else {
+    sem_wait(barrier);
+    sem_post(barrier);
+  }
+}
+
+void destroy_barrier(int my_pid) {
+  if (my_pid != 0) {
+    sem_destroy(barrier);
+    sem_destroy(countMut);
+    shmdt(count);
+    shmdt(barrier);
+    shmdt(countMut);
+    shmctl(countShmId, IPC_RMID, 0);
+    shmctl(barrierShmId, IPC_RMID, 0);
+    shmctl(countMutShmId, IPC_RMID, 0);
+    // Destroy the semaphores and detach
+    // and free any shared memory. Notice
+    // that we explicity check that it is
+    // the parent doing it.
+  }
+}