Document Message Queue variables.

[wsti_so.git] / src / process3.c

diff --git a/src/process3.c b/src/process3.c
index dfa30dbe389d56ab4cc24f5bf3206fde813c0d94..91212e991a1cc3ff0363e1a8f157fa5df5a7bc8b 100644 (file)
--- a/src/process3.c
+++ b/src/process3.c
@@ -1,25 +1,177 @@
 #include <stdio.h>
 
+/* exit.. */
+#include <stdlib.h>
+/* strsignal... */
+#include <string.h>
+
 /* open/read/write/close */
 #include <fcntl.h>
 
+/* 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;
+
+
+/**
+ * Shared memory variables
+ */
+/**
+ * Memory key for processes. Must be same between all processes to properly
+ * communicate.
+ */
+key_t shmkey = 18912;
+/**
+ * Id of the shared memory
+ */
+int shmid;
+
+/**
+ * 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) {
-       /** Named pipe used to communicate with process2 */
-       char * read_pipe = "/tmp/process2pipe";
-
-       /** Descriptor of input pipe */
-       int read_descriptor;
-
        /** Buffer used for storing data from input pipe */
        int buffer = 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);
 
@@ -37,6 +189,7 @@ int main(void) {
                }
        }
 
+       /* Release resources in normal program flow exit. */
        close(read_descriptor);
 
        return 0;