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main.c
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main.c
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#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <stdlib.h>
#include <math.h>
#define TXTSIZE 80 //megisto plhthos bytes apo ta aopoia tha apoteleitai kathe mhnyma pou diakineitai
#define MESNUM 2 //plhthos synolikwn dosolhpsiwn (LEEI STHN EKFWNHSH NA DINETAI WS PARAMETROS.. NA MHN KSEXASW NA TO FTIAKSW)
typedef struct sharedmem_in {
int filedesc;
int cur_pid;
} Shm_in;
typedef struct sharedmem_out {
char* buf[80];
} Shm_out;
union semun {
int val;
struct semid_ds *buf;
ushort *array;
};
int main(void) {
int semin, semread, semout,semlog;
union semun arg;
struct sembuf semopr;
int shmid_in;/*id of in-share-memory*/
int shmid_out;/*id of out-share-memory*/
Shm_in* shm1;/*pointer to in-share-memory*/
Shm_out* shm2;/*pointer to out-share-memory*/
pid_t pid;/*to pid tou process*/
/*******************************************************************/
/*create the 2 shared-memory segments and attach the 2 segments*/
if ( ((shmid_in = shmget(1234, sizeof(Shm_in), 0666 | IPC_CREAT)) < 0 ) ||
((shmid_out = shmget(5678, TXTSIZE+1, 0666 | IPC_CREAT)) < 0) ) {
perror("shmget");
exit(1);
}
/**/
if ( ((shm1 = shmat(shmid_in,0,0)) == (char*) -1) ||
((shm2 = shmat(shmid_out,0,0)) == (char*) -1) ) {
perror("shmat");
exit(1);
}
/*******************************************************************/
/* Create semaphores*/
semin = semget((key_t) 111, 1, IPC_CREAT | 0660);
semread = semget((key_t) 222, 1, IPC_CREAT | 0660);
semout = semget((key_t) 333, 1, IPC_CREAT | 0660);
semlog = semget((key_t) 444, 1, IPC_CREAT | 0660);
if ( (semin == -1) || (semread == -1) || (semout == -1) || (semlog == -1) )
exit(-1);
/*initialize semaphores*/
arg.val=1;
semctl(semin, 0, SETVAL, arg);//semin se up
semctl(semout, 0, SETVAL, arg);//semout se up
arg.val=0;
semctl(semread, 0, SETVAL, arg);//semread se down
semctl(semlog, 0, SETVAL, arg);//semctl se down
/*fork and check with switch if it is the parent (pid != 0, the program C) or the child (pid=0, the program S)*/
pid=fork();
/*if error..*/
if(pid == -1 ) {
perror("fork");exit(1);
}
/**/
/*...else if, it is the child process-S program*/
else if (pid == 0) {
printf("I'm process S - the child\n");
int counter=0;
while(counter < MESNUM) {//oso exw akoma aithseis gia na staloun
/*down(semread)*/
semopr.sem_num = 0;
semopr.sem_op = -1;
semopr.sem_flg = 0;
semop(semread, &semopr, 1);
//EDW DIAVAZW TA PERIEXOMENA TOU IN//
/*up(semin)*/
semopr.sem_num = 0;
semopr.sem_op = 1;
semopr.sem_flg = 0;
semop(semin, &semopr, 1);
if(fork() != 0 ) { //it is S again..
continue;
}
else {//it is S'...
//PAIRNW TO PID KAI TO ZHTOUMENO KEIMENO - DHLADH TA PERIEXOMENA TOU OUT, KAI TA EPEKSERGAZOMAI//
/*apoktaw prosvash ston semtemp tou antistoixou C' tou opoiou exw to pid*/
int semtempc = semget((key_t) pid /*TO PID POU MOLIS ELAVA*/, 1, IPC_CREAT | 0660);
/*down(out)*/
semopr.sem_num = 0;
semopr.sem_op = -1;
semopr.sem_flg = 0;
semop(semout, &semopr, 1);
//EDW GRAFW STO OUT TO PERIEXOMENO TOU TXT//
/*up(semptempc)*/
semopr.sem_num = 0;
semopr.sem_op = 1;
semopr.sem_flg = 0;
semop(semtempc, &semopr, 1);
//kai twra kleinw...//
exit(0);
}
}
}
/**/
/*...else, if it is the parent process-C program*/
else{
int i;
/*for(i=0;i<MESNUM;i++) {
//if(temp == EKTHETIKH...)*/
if (fork() != 0 ) { //it's the C again ..
//continue;
printf("ITS THE C A G A I N ! ! ! \n");
}
else { //it is C'..
/* Create a semaphore semtemp for current process C'*/
int semtemp = semget((key_t) getpid(), 1, IPC_CREAT | 0660);
if (semtemp == -1) exit(-1);
/*Initialize it to down*/
arg.val=0;
semctl(semtemp, 0, SETVAL, arg);
/*down(semin)*/
semopr.sem_num = 0;
semopr.sem_op = -1;
semopr.sem_flg = 0;
semop(semin, &semopr, 1);
//GRAFW EDW TO STOIXEIO STHN IN MEMORY//
/*up(semread)*/
semopr.sem_num = 0;
semopr.sem_op = 1;
semopr.sem_flg = 0;
semop(semread, &semopr, 1);
/*down(semtemp)*/
semopr.sem_num = 0;
semopr.sem_op = -1;
semopr.sem_flg = 0;
semop(semtemp, &semopr, 1);
//EDW DIAVAZEI TA PERIEXOMENA TOU OUT//
/*up(semout)*/
semopr.sem_num = 0;
semopr.sem_op = 1;
semopr.sem_flg = 0;
semop(semout, &semopr, 1);
/*down(semlog)*/
semopr.sem_num = 0;
semopr.sem_op = -1;
semopr.sem_flg = 0;
semop(semtemp, &semopr, 1);
//EDW GRAFEI STO LOG.TXT
/*up(semlog)*/
semopr.sem_num = 0;
semopr.sem_op = 1;
semopr.sem_flg = 0;
semop(semlog, &semopr, 1);
}
/*}*/
}
/**/
/*delete semaphores*/
semctl(semin, 0, IPC_RMID, 0);
semctl(semout, 0, IPC_RMID, 0);
semctl(semread, 0, IPC_RMID, 0);
semctl(semlog, 0, IPC_RMID, 0);
/*deattach memory segments*/
if( (shmdt(shm1) == -1 ) || (shmdt(shm2) == -1) ) {
perror("shmdt");
exit(1);
}
/**/
/*destroy memory segments*/
if ( (shmctl(shmid_in,IPC_RMID,0) == -1) || (shmctl(shmid_out,IPC_RMID,0) == -1) ) {
perror("shmctl");
exit(1);
}
/**/
return 0;
}