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Author: Shrish Bhargav

main.c

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+// #include <stdio.h>
+// #include <pthread.h>    // header file for multithreading
+// #include <semaphore.h>
+// #include <unistd.h>
+
+// // sem_t struct is alreading defined inside of the <semaphore.h>
+
+// sem_t mutex; 
+
+// void* thread(void* arg)
+// {
+//     //wait
+//     sem_wait(&mutex);   // lock or wait
+//     printf("\nEntered...\n");
+
+//     //important 
+//     sleep(4); 
+
+//     //signal - which we had discussed in the previous video also
+//     printf("\n Just Exiting\n");
+//     sem_post(&mutex); // this is used to release the signal. 
+// }
+
+// int main() {
+//     sem_init(&mutex, 0, 1);
+//     pthread_t t1, t2, t3; // let us create three threads
+//     pthread_create(&t1, NULL, thread, NULL);
+//     sleep(2);
+//     pthread_create(&t2, NULL, thread, NULL);
+//     sleep(2);
+//     pthread_create(&t3, NULL, thread, NULL);
+//     pthread_join(t1, NULL);
+//     pthread_join(t2, NULL);
+//     pthread_join(t3, NULL);
+//     sem_destroy(&mutex);    // destroy the semaphore
+
+//     return 0 ;
+// }
+
+/*
+*   The Single Producer-Consumer Problem
+*   1. Shared Buffer
+*   2. Producer Thread
+*   3. Consumer Thread
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>        // we will use this to create the producer and consumer threads
+#include <semaphore.h>
+#include <unistd.h>         // this header file has the sleep() function definition.
+
+#define MAX_SIZE 10
+
+sem_t mutex;
+int queue[MAX_SIZE];
+int front = -1, rear = -1;
+
+int isFull()
+{
+    return (rear+1)%MAX_SIZE == front;
+}
+
+int isEmpty()
+{
+    return front == -1;
+}
+
+// function to enqueue(insert) an element
+void* enqueue(void* arg) {
+    
+    if(isFull()) {
+        printf("Queue Overflow");
+        return 0;
+    }
+
+    if(front == -1) {
+        front = 0;
+    }
+
+    rear = (rear+1)%MAX_SIZE;
+    printf("Buffer can be shared\n");
+}
+
+// function to dequeue(remove) an element
+void* dequeue(void* arg) {
+    
+    if(isEmpty()) {
+        printf("Queue underflow\n");
+        printf("Buffer cannot be shared now");
+        exit(1);
+    }
+
+    if(front == rear) {
+        front = rear = -1;
+    }else {
+        front = (front+1)%MAX_SIZE;
+    }
+}
+
+
+
+int main() {
+    sem_init(&mutex, 0, 1);
+    pthread_t thread_producer, thread_consumer;
+    
+    pthread_create(&thread_producer, NULL, enqueue, NULL);
+    sleep(2);
+
+    pthread_create(&thread_producer, NULL, enqueue, NULL);
+    sleep(2);
+
+    pthread_create(&thread_consumer, NULL, dequeue, NULL);
+    sleep(2);
+
+    pthread_create(&thread_consumer, NULL, dequeue, NULL);
+    sleep(2);
+
+    pthread_create(&thread_consumer, NULL, dequeue, NULL);
+    pthread_join(thread_producer, NULL);
+    pthread_join(thread_consumer, NULL);
+
+    sem_destroy(&mutex);
+
+    return 0;
+}
+
+