Added initial inter-process communication: Sharing pids between processes.

[wsti_so.git] / src / process1.c

diff --git a/src/process1.c b/src/process1.c
index d0b8e19135969cf98be9cc36f7c305c781107ac8..b28563f4102faf831cf12deecd2ff440eb3b0216 100644 (file)
--- a/src/process1.c
+++ b/src/process1.c
@@ -5,9 +5,81 @@
 /* open/read/write/close */
 #include <fcntl.h>
 
+/* Signals handling.. */
+#include <signal.h>
+
+#include <sys/shm.h>
+
+
 /** If buffer is too small to hold entire string, it is incremented by this value */
 #define BUFFER_STEP 16
 
+/** Buffer used to store line of characters */
+char * buffer = NULL;
+
+/** Named pipe used to communnicate with process2 */
+char * write_pipe = "/tmp/process1pipe";
+
+/** File descriptor of pipe */
+int file_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;
+
+/**
+ * Message shared by processes. Contains array of process IDs
+ */
+struct message {
+       pid_t pids[3];
+};
+
+struct message * processes = NULL;
+
+/**
+ * Handler for signals.
+ */
+void sig_handler(int signo)
+{
+       fprintf(stderr, "[%s] Received %s!\n", "process1", strsignal(signo));
+       if (signo == SIGUSR1) {
+       }
+       else if (signo == SIGTERM) {
+               int i = 0;
+               fprintf(stderr, "[%s] > Releasing resources\n", "process1");
+               close(write_pipe);
+               unlink(write_pipe);
+
+               if (buffer) {
+                       free(buffer);
+                       buffer = NULL;
+               }
+               for (; i < 3; i++) {
+                       fprintf(stderr, "[%s] Process %d, PID: %d\n", "process3", i, processes->pids[i]);
+               }
+               exit(0);
+       }
+       else if (signo == SIGTSTP) {
+               fprintf(stderr, "[%s] > Closing pipe\n", "process1");
+               close(write_pipe);
+               raise (SIGSTOP);
+       }
+       else if (signo == SIGCONT) {
+               fprintf(stderr, "[%s] > Opening pipe\n", "process1");
+               file_descriptor = open(write_pipe, O_WRONLY);
+       }
+}
+
 /**
  * Program reads entire lines of text from the standard input and pass them
  * to the process2 using created pipe.
@@ -16,9 +88,6 @@ int main(void) {
        /** Currently fetched from stdin character */
        int c;
 
-       /** Buffer used to store line of characters */
-       char * buffer = NULL;
-
        /** Current buffer length*/
        int buffer_length = 0;
 
@@ -31,16 +100,37 @@ int main(void) {
         */
        char * tmp = NULL;
 
-       /** Named pipe used to communnicate with process2 */
-       char * write_pipe = "/tmp/process1pipe";
+       fprintf(stderr, "[%s] Init!\n", "process1");
 
-       /** File descriptor of pipe */
-       int file_descriptor;
+       /**
+        * 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), IPC_CREAT | 0666);
+
+       processes = (struct message *)shmat(shmid, NULL, 0);
+       processes->pids[0] = getpid();
 
        mkfifo(write_pipe, 0666);
 
        file_descriptor = open(write_pipe, O_WRONLY);
-       
+
        do {
                c = fgetc(stdin);
 
@@ -97,6 +187,7 @@ int main(void) {
                }
        } while(c != EOF);
 
+       /* Release resources in normal program flow exit. */
        close(write_pipe);
        unlink(write_pipe);