#include <stdio.h>
+
+/* exit.. */
#include <stdlib.h>
+/* strsignal... */
#include <string.h>
/* open/read/write/close */
#include <fcntl.h>
-/** If buffer is too small to hold entire string, it is incremented by this value */
-#define BUFFER_STEP 16
+/* Signals handling.. */
+#include <signal.h>
+
+#include <sys/shm.h>
+#include <sys/msg.h>
+
+/** Named pipe used to communicate with process2 */
+char * read_pipe = "/tmp/process2pipe";
+
+/** Descriptor of input pipe */
+int read_descriptor;
+
/**
- * Program grabs data from process1, calculates number of characters in each line
- * and pass the value to process3.
+ * Shared memory variables
*/
-int main(void) {
- /** Named pipe used to communicate with process1 */
- char * read_pipe = "/tmp/process2pipe";
+/**
+ * Memory key for processes. Must be same between all processes to properly
+ * communicate.
+ */
+key_t shmkey = 18912;
+/**
+ * Id of the shared memory
+ */
+int shmid;
- int read_descriptor;
-
+/**
+ * Structure holding array of process IDs.
+ * Message is shared by processes. Contains array of process IDs
+ */
+struct message {
+ pid_t pids[3];
+};
+
+struct message * processes = NULL;
+
+/**
+ * Message Queue variables
+ */
+
+/**
+ * Unique key of message queue.
+ */
+key_t qkey = 12356;
+
+/**
+ * Queue descriptor.
+ */
+int qid;
+
+/**
+ * Structure holding queue message data.
+ * Parameter mtype describes process to whom message is sent.
+ * Parameter signo is a signal to raise after getting message.
+ */
+struct queue_message {
+ long mtype;
+ int signo[1];
+};
+
+void notify_other_processes(int signo) {
+ int i = 0;
+ struct queue_message msg;
+ msg.signo[0] = signo;
+
+ for (; i < 3; i++) {
+ pid_t pid = processes->pids[i];
+ // Bleh
+ if (i != 2 && pid != 0) {
+ msg.mtype = i+1;
+ fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process3", msg.mtype, msg.signo[0]);
+ msgsnd(qid, &msg, sizeof(int), 0);
+ fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process3", strsignal(SIGUSR1), SIGUSR1, pid);
+ kill(pid, SIGUSR1);
+ }
+ }
+}
+
+/**
+ * Handler for signals.
+ */
+void sig_handler(int signo)
+{
+ fprintf(stderr, "[%s] Received %s!\n", "process3", strsignal(signo));
+ if (signo == SIGUSR1) {
+ fprintf(stderr, "[%s] > Notified!\n", "process3");
+ struct queue_message msg;
+ /* Check queues from both other processes */
+ if (msgrcv(qid, &msg, sizeof(int), 3, 0) > 0) {
+ fprintf(stderr, "[%s] > Notified with value: %s!\n", "process3", strsignal(msg.signo[0]));
+ raise(msg.signo[0]);
+ }
+ }
+ else if (signo == SIGTERM) {
+ fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
+ processes->pids[2] = 0;
+ notify_other_processes(signo);
+
+ fprintf(stderr, "[%s] > Releasing resources\n", "process3");
+ close(read_descriptor);
+ exit(0);
+ }
+ else if (signo == SIGTSTP) {
+ fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
+ notify_other_processes(signo);
+
+ fprintf(stderr, "[%s] > Closing pipe\n", "process3");
+ close(read_descriptor);
+ raise (SIGSTOP);
+ }
+ else if (signo == SIGCONT) {
+ fprintf(stderr, "[%s] > Signalling other processes..\n", "process3");
+ notify_other_processes(signo);
+
+ fprintf(stderr, "[%s] > Opening pipe\n", "process3");
+ read_descriptor = open(read_pipe, O_RDONLY);
+ }
+}
+
+/**
+ * Program grabs data (calculated number of characters) from process2 and prints
+ * grabbed data to the standard output.
+ */
+int main(void) {
+ /** Buffer used for storing data from input pipe */
int buffer = 0;
- int i = 0;
+ /** Stores number of bytes read from input pipe in current iteration */
ssize_t count = 0;
+ fprintf(stderr, "[%s] Init!\n", "process3");
+
+ /**
+ * Register signals handled by process
+ */
+ if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
+ fprintf(stderr, "can't catch SIGUSR1\n");
+ }
+ if (signal(SIGTERM, sig_handler) == SIG_ERR) {
+ fprintf(stderr, "can't catch SIGTERM\n");
+ }
+ if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
+ fprintf(stderr, "can't catch SIGTSTP\n");
+ }
+ if (signal(SIGCONT, sig_handler) == SIG_ERR) {
+ fprintf(stderr, "can't catch SIGCONT\n");
+ }
+
+ /*
+ * Register memory to share with other processes, and pass current
+ * process id to the array.
+ */
+ shmid = shmget(shmkey, sizeof(struct message), 0666);
+
+ processes = (struct message *)shmat(shmid, NULL, 0);
+ processes->pids[2] = getpid();
+
+ fprintf(stderr, "[%s] Shared pid: %d\n", "process3", getpid());
+
+ /**
+ * Register message queue to communicate with other processes
+ */
+ qid = msgget(qkey, 0666);
+
/* Reading from process2 */
read_descriptor = open(read_pipe, O_RDONLY);
- int number_of_characters = 0;
-
while(1) {
/* Read data from input pipe */
count = read(read_descriptor, &buffer, sizeof(int));
}
}
+ /* Release resources in normal program flow exit. */
close(read_descriptor);
return 0;