int client(void)
{
int s;
/* spingrab in order to avoid sleep, testcase has a timeout */
while ( (s = msemgrab(SEM0, 0)) == -1 );
int cnt = 0;
for (int i = 0; i < 5; ++i) {
if (msemdown(s, 1, 1) != 0) {
if (errno == EINTR) {
/* interrupted by syscall, try again */
continue;
}
perror("mP(1)");
break;
}
printf("c%d", cnt);
cnt += 2;
fflush(stdout);
if (msemup(s, 1, 0) != 0) {
perror("mV(0)");
break;
}
}
return 0;
}
/**
* Write buffer to shared memory
*
* @param data buffer to write to shared memory
*
* @return -1 on error, 0 otherwise
*/
static int ipc_write(char *data)
{
int ret = -1;
/* It makes no sense to proceed if nobody is listening */
ipc_require_listener();
/*
* Firts wait for write queue to let us in
* if cnd or mt are no valid semaphores anymore, another process has already removed them. so we will simply return -1
*/
if(msemdown(cnd, 1, 0) != -1) {
/* While we are in the mutual exclusive section, we don't listen to signals, because it would be hard to reset the state of the mutex */
sigset_t blocked_signals, curr_set;
(void) sigfillset(&blocked_signals);
(void) sigprocmask(SIG_BLOCK, &blocked_signals, &curr_set);
/* Mutual exclusive section so no other process removes shm segment meanwhile */
if(semdown(mtx) != -1) {
if(data == NULL) {
/* Signal EOF to Listener */
shared->flag |= EOF_F;
} else {
for(int i = 0; i <= MAX_BUF_SIZE; ++i) {
shared->data[i] = data[i];
/* Null char */
if(data[i] == 0) {
break;
}
}
}
ret = (semup(mtx) == -1 ? -1 : 0);
}
/* Reset to original procmask*/
(void) sigprocmask(SIG_SETMASK, &curr_set, NULL);
/* Signal read queue to proceed */
ret = (msemup(cnd, 1, 1) == -1 ? -1 : 0);
}
return ret;
}
/**
* Read shared data and calculate statistics
*
* @return -1 on error, 0 on EOF, number of read chars otherwise
*/
static int ipc_process(void)
{
int i = -1;
/*
* First, wait for read queue to let us in
* if cnd or mt are no valid semaphores anymore, another process has already removed them. so we will simply return -1
*/
if(msemdown(cnd, 1, 1) != -1) {
/* While we are in the mutual exclusive section, we don't listen to signals, because it would be hard to reset the state of the mutex */
sigset_t blocked_signals, curr_set;
(void) sigfillset(&blocked_signals);
(void) sigprocmask(SIG_BLOCK, &blocked_signals, &curr_set);
/* Mutual exclusive section so no other process removes shm segment meanwhile */
if(semdown(mtx) != -1) {
i = 0;
/* EOF Flag has been set, return 0 */
if((shared->flag & EOF_F) != 1) {
for(i = 0; i <= MAX_BUF_SIZE; ++i) {
int c;
/* Null character */
if(shared->data[i] == 0) {
break;
}
/* We will only distinguish between uppercase'd chars */
c = toupper(shared->data[i]) - ASCII_CHAR_OFFSET;
if(c < 0 || c > ASCII_CHAR_MAX) { /* No Ascii Letter -> inc 'others' counter */
shared->stat[ASCII_CHAR_MAX + 1]++;
} else { /* inc letter counter */
shared->stat[c]++;
}
/* Total number of characters */
shared->total++;
/* Clear out buffer */
shared->data[i] = 0;
}
}
if(semup(mtx) == -1) {
i = -1;
}
}
/* Reset to original procmask*/
(void) sigprocmask(SIG_SETMASK, &curr_set, NULL);
/* Let write queue proceed */
if(msemup(cnd, 1, 0) == -1) {
i = -1;
}
}
return i;
}
