bool JdbcUtil::lockSemaphore(unsigned short sem_idx, bool lock)
{
setError(NULL);
if (lock && !getSemaphores(false)) return false;
const char *lock_str;
if (lock) lock_str = "lock";
else lock_str = "unlock";
if (semaphoreId==-1)
{
char rc[80];
sprintf(rc,"Cannot %s semaphore when semaphore not attached",lock_str);
setError(rc);
return false;
}
struct sembuf sem_op;
sem_op.sem_num = sem_idx;
if (lock) sem_op.sem_op = -1;
else sem_op.sem_op = 1;
sem_op.sem_flg = 0;
if (semop(semaphoreId,&sem_op,1)==-1)
{
char rc[80];
sprintf(rc,"Error during %s of semaphore",lock_str);
setError(rc);
return false;
}
return true;
}
int main(int argc, char *argv[])
{
int i;
struct sems *s = getSemaphores();
if (s == NULL) {
errExit("getSemaphores");
}
printf("key\t\tsemid\t\towner\t\tperms\t\tnsems\n");
for (i = 0; i < s->len; i++) {
printf(
"0x%08x\t%d\t\t%s\t\t%o\t\t%d\n",
s->info[i].key,
s->info[i].semid,
userNameFromId(s->info[i].uid),
s->info[i].perms,
s->info[i].nsems
);
}
free(s->info);
free(s);
exit(EXIT_SUCCESS);
}
int main(int argc, char const *argv[])
{
if (argc != 2)
{
printf("usage: %s <data file>\n", argv[0]);
exit(4);
}
int semaphores = getSemaphores();
semaphoreWait(semaphores, WRITER);
FILE* outputFile;
outputFile = fopen(argv[1], "w");
if (outputFile == 0)
{
printf("error: couldn't open output file");
exit(5);
}
StudentInfo* basePointer = getSharedMemoryPointer();
StudentInfo* currentPointer = basePointer;
for (int i = 0; i < MAX_STUDENTS; ++i)
{
fprintf(outputFile, "%s\n", currentPointer->studentName);
fprintf(outputFile, "%s\n", currentPointer->studentID);
fprintf(outputFile, "%s\n", currentPointer->address);
fprintf(outputFile, "%s\n", currentPointer->telephoneNumber);
currentPointer++;
}
fclose(outputFile);
detachSharedMemoryPointer(basePointer);
destroySharedMemory();
destroyReadCount();
semaphoreSignal(semaphores, WRITER);
destroySemaphores(semaphores);
return 0;
}
bool JdbcUtil::memoryInit(void)
{
setError(NULL);
if (!removeMemory()) return false;
if (!removeSemaphores()) return false;
if (!getMemory(true)) return false;
if (!attachMemory()) return false;
memset(sharedMemory,0,SHARED_MEMORY_SIZE);
sharedMemory->active = true;
if (!getSemaphores(true)) return false;
if (semctl(semaphoreId, 0, SETVAL, 1) == -1)
{
int err = errno;
removeMemory();
removeSemaphores();
setPerror(err,"Cannot initialize semaphore value");
return false;
}
return true;
}
int main(void) {
// create shared memory buffer with rw perms
int shmid = shmget(1000, 1, IPC_CREAT | PERMS);
if(shmid < 0) {
fprintf(stderr, "Unable to create shared buffer.\n");
exit(EXIT_FAILURE);
}
// allocate buffer
if((buffer = (int*)shmat(shmid, (char*)0, 0)) == (int*)-1) {
fprintf(stderr, "Unable to allocate.\n");
exit(EXIT_FAILURE);
}
// use smget to get semaphores with read write permissions
getSemaphores();
// initialize semaphores
createSemaphores();
// create child processes
int pid_tob = fork();
if(pid_tob < 0) { perror("pid_tob"); exit(EXIT_FAILURE); }
if(pid_tob == 0) {
while(1) {
// in smoker with tobacco
P(stob); // wait for signal
P(smutex); // wait to modify buffer
smoker_t(); // roll up cigarette
V(sage); // signal agent
V(smutex); // signal that buffer can now be modified again
}
}else {
int pid_pap = fork();
if(pid_pap < 0) { perror("pid_pap"); exit(EXIT_FAILURE); }
if(pid_pap == 0) {
while(1) {
// in smoker with paper
P(spap);
P(smutex);
smoker_p();
V(sage);
V(smutex);
}
}else {
int pid_mat = fork();
if(pid_mat < 0) { perror("pid_mat"); exit(EXIT_FAILURE); }
if(pid_mat == 0) {
while(1) {
// in smoker with matches
P(smat);
P(smutex);
smoker_m();
V(sage);
V(smutex);
}
}else {
// in agent
int i;
for(int i = 0; i < N; ++i) {
P(smutex); // wait for signal to modify buffer
agent(); // place items on table
// signal the smoker with the remaining item
int supply = *buffer;
if(supply == TOBACCO) V(stob);
else if(supply == PAPER) V(spap);
else V(smat);
V(smutex); // done modifying buffer
P(sage); // now wait while a smoker process loop finishes
putchar('\n');
}
// infinite loop, so kill child processes on exit
kill(pid_pap, SIGUSR1);
kill(pid_tob, SIGUSR1);
kill(pid_mat, SIGUSR1);
exit(EXIT_SUCCESS);
}
}
}
}