flag.c

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <time.h> 
#include <sys/types.h> 
#include <sys/ipc.h> 
#include <sys/shm.h> 
#include <stdbool.h> 
#define _BSD_SOURCE 
#include <sys/time.h> 
#include <stdio.h> 

#define BSIZE 2 // Buffer size 
#define PWT 2 // Producer wait time limit 
#define CWT 5 // Consumer wait time limit 
#define RT 17 // Program run-time in seconds 

int shmid1, shmid2, shmid3, shmid4; 
key_t k1 = 5491, k2 = 5812, k3 = 4327, k4 = 3213; 
bool* SHM1; 
int* SHM2; 
int* SHM3; 

int myrand(int n) // Returns a random number between 1 and n 
{ 
	time_t t; 
	srand((unsigned)time(&t)); 
	return (rand() % n + 1); 
} 

int main() 
{ 
	shmid1 = shmget(IPC_PRIVATE, sizeof(bool) * 2, IPC_CREAT | 0660); // flag 
	//shmid2 = shmget(k2, sizeof(int) * 1, IPC_CREAT | 0660); // turn 
	shmid3 = shmget(IPC_PRIVATE, sizeof(int) * BSIZE, IPC_CREAT | 0660); // buffer 
	shmid4 = shmget(IPC_PRIVATE, sizeof(int) * 1, IPC_CREAT | 0660); // time stamp 

	if (shmid1 < 0 || shmid3 < 0 || shmid4 < 0) { 
		perror("Main shmget error: "); 
		exit(1); 
	} 
	SHM3 = (int*)shmat(shmid3, NULL, 0); 
	int ix = 0; 
	while (ix < BSIZE) // Initializing buffer 
		SHM3[ix++] = 0; 

	struct timeval t; 
	time_t t1, t2; 
	gettimeofday(&t, NULL); 
	t1 = t.tv_sec; 

	int* state = (int*)shmat(shmid4, NULL, 0); 
	*state = 1; 
	int wait_time; 

	int i = 0; // Consumer 
	int j = 1; // Producer 

	if (fork() == 0) // Producer code 
	{ 
		SHM1 = (bool*)shmat(shmid1, NULL, 0); 
		//SHM2 = (int*)shmat(shmid2, NULL, 0); 
		SHM3 = (int*)shmat(shmid3, NULL, 0); 
		if (SHM1 == (bool*)-1 || SHM3 == (int*)-1) { 
			perror("Producer shmat error: "); 
			exit(1); 
		} 

		bool* flag = SHM1; 
		//int* turn = SHM2; 
		int* buf = SHM3; 
		int index = 0; 

		while (*state == 1) { 
			flag[j] = true; 
			printf("Producer is ready now.\n\n"); 
			//*turn = i; 
			while (flag[i] == true) 
				; 

			// Critical Section Begin 
			index = 0; 
			while (index < BSIZE) { 
				if (buf[index] == 0) { 
					int tempo = myrand(BSIZE * 3); 
					printf("Job %d has been produced\n", tempo); 
					buf[index] = tempo; 
					break; 
				} 
				index++; 
			} 
			if (index == BSIZE) 
				printf("Buffer is full, nothing can be produced!!!\n"); 
			printf("Buffer: "); 
			index = 0; 
			while (index < BSIZE) 
				printf("%d ", buf[index++]); 
			printf("\n"); 
			// Critical Section End 

			flag[j] = false; 
			if (*state == 0) 
				break; 
			wait_time = myrand(PWT); 
			printf("Producer will wait for %d seconds\n\n", wait_time); 
			sleep(wait_time); 
		} 
		exit(0); 
	} 

	if (fork() == 0) // Consumer code 
	{ 
		SHM1 = (bool*)shmat(shmid1, NULL, 0); 
		//SHM2 = (int*)shmat(shmid2, NULL, 0); 
		SHM3 = (int*)shmat(shmid3, NULL, 0); 
		if (SHM1 == (bool*)-1 || SHM3 == (int*)-1) { 
			perror("Consumer shmat error:"); 
			exit(1); 
		} 

		bool* flag = SHM1; 
	//	int* turn = SHM2; 
		int* buf = SHM3; 
		int index = 0; 
		flag[i] = false; 
		sleep(5); 
		while (*state == 1) { 
			flag[i] = true; 
			printf("Consumer is ready now.\n\n"); 
		 
			while (flag[j] == true) 
				; 

			// Critical Section Begin 
			if (buf[0] != 0) { 
				printf("Job %d has been consumed\n", buf[0]); 
				buf[0] = 0; 
				index = 1; 
				while (index < BSIZE) // Shifting remaining jobs forward 
				{ 
					buf[index - 1] = buf[index]; 
					index++; 
				} 
				buf[index - 1] = 0; 
			} else
				printf("Buffer is empty, nothing can be consumed!!!\n"); 
			printf("Buffer: "); 
			index = 0; 
			while (index < BSIZE) 
				printf("%d ", buf[index++]); 
			printf("\n"); 
			// Critical Section End 

			flag[i] = false; 
			if (*state == 0) 
				break; 
			wait_time = myrand(CWT); 
			printf("Consumer will sleep for %d seconds\n\n", wait_time); 
			sleep(wait_time); 
		} 
		exit(0); 
	} 
	// Parent process will now for RT seconds before causing child to terminate 
	while (1) { 
		gettimeofday(&t, NULL); 
		t2 = t.tv_sec; 
		if (t2 - t1 > RT) // Program will exit after RT seconds 
		{ 
			*state = 0; 
			break; 
		} 
	} 
	// Waiting for both processes to exit 
	wait(); 
	wait(); 
	printf("The clock ran out.\n"); 
	return 0; 
}