67 lines
2.0 KiB
C++
67 lines
2.0 KiB
C++
//
|
|
// Created by Cigerxwin Chaker on 05.11.19.
|
|
//
|
|
#include <iostream>
|
|
#include <sys/types.h>
|
|
#include <sys/ipc.h>
|
|
#include <sys/shm.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/sem.h>
|
|
#include <unistd.h>
|
|
#include <cstring>
|
|
|
|
#include "SharedMemoryAccess.h" /* header is important for the shmID. name could be different. maybe not needed cause: (shmget(memory_access_key, NULL, 0)) */
|
|
|
|
int initSemaphore (void) {
|
|
/* Testen, ob das Semaphor bereits existiert */
|
|
semId = semget (SEM_KEY, 0, IPC_PRIVATE);
|
|
if (semId < 0) {
|
|
/* ... existiert noch nicht, also anlegen */
|
|
/* Alle Zugriffsrechte der Dateikreierungsmaske */
|
|
/* erlauben */
|
|
umask(0);
|
|
semId = semget (SEM_KEY, 1, IPC_CREAT | IPC_EXCL | PERM);
|
|
if (semId < 0) {
|
|
return -1;
|
|
}
|
|
/* Semaphor mit 1 initialisieren */
|
|
if (semctl (semId, 0, SETVAL, (int) 1) == -1)
|
|
return -1;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
int semaphoreOperation (int op) {
|
|
semaphore.sem_op = op;
|
|
semaphore.sem_flg = SEM_UNDO;
|
|
if( semop (semId, &semaphore, 1) == -1) {
|
|
perror(" semop ");
|
|
exit (EXIT_FAILURE);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
void writeToShm(char* text, int size) {
|
|
int shmId = shmget(memoryAccessKey, NULL, 0); // dont init just get the ID if already existing.
|
|
if(shmId < 0 ) {
|
|
exit(EXIT_FAILURE);
|
|
/* we could return -1, not sure if it will be useful to continue after there is no shm allocated for any reason*/
|
|
} else {
|
|
char *shm_pointer = (char *) shmat(shmId, NULL, 0);
|
|
semaphoreOperation(LOCK);
|
|
memcpy(shm_pointer, text, size);
|
|
semaphoreOperation(UNLOCK);
|
|
}
|
|
}
|
|
|
|
char* getShmPointer() {
|
|
int shmId = shmget(memoryAccessKey, NULL, 0);
|
|
if(shmId < 0) {
|
|
exit(EXIT_FAILURE);
|
|
/* we could return -1, not sure if it will be useful to continue after there is no shm allocated for any reason*/
|
|
} else {
|
|
return (char *) shmat(shmId, NULL, 0);
|
|
}
|
|
} |