src/process1.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4
   5 /* open/read/write/close */
   6 #include <fcntl.h>
   7
   8 /* Signals handling.. */
   9 #include <signal.h>
  10
  11 #include <sys/shm.h>
  12 #include <sys/msg.h>
  13
  14
  15 /** If buffer is too small to hold entire string, it is incremented by this value */
  16 #define BUFFER_STEP 16
  17
  18 /** Buffer used to store line of characters */
  19 char * buffer = NULL;
  20
  21 /** Named pipe used to communnicate with process2 */
  22 char * write_pipe = "/tmp/process1pipe";
  23
  24 /** File descriptor of pipe */
  25 int file_descriptor;
  26
  27
  28 /**
  29  * Shared memory variables
  30  */
  31 /**
  32  * Memory key for processes. Must be same between all processes to properly
  33  * communicate.
  34  */
  35 key_t shmkey = 18912;
  36 /**
  37  * Id of the shared memory
  38  */
  39 int shmid;
  40
  41 /**
  42  * Message shared by processes. Contains array of process IDs
  43  */
  44 struct message {
  45         pid_t pids[3];
  46 };
  47
  48 struct message * processes = NULL;
  49
  50 /**
  51  * Message queue variables
  52  */
  53 key_t qkey;
  54 int qid_input;
  55
  56 int qid_output1;
  57 int qid_output2;
  58
  59 struct queue_message {
  60         long mtype;
  61         int signo[1];
  62 };
  63
  64 void notify_other_processes(int signo) {
  65         int i = 0;
  66         struct queue_message msg;
  67         msg.signo[0] = signo;
  68
  69         for (; i < 3; i++) {
  70                 pid_t pid = processes->pids[i];
  71                 // Bleh
  72                 if (i != 0 && pid != 0) {
  73                         msg.mtype = i+1;
  74                         fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process1", msg.mtype, msg.signo[0]);
  75                         msgsnd(pid, &msg, sizeof(int), 0);
  76                         fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process1", strsignal(SIGUSR1), SIGUSR1, pid);
  77                         kill(pid, SIGUSR1);
  78                 }
  79         }
  80 }
  81
  82 /**
  83  * Handler for signals.
  84  */
  85 void sig_handler(int signo)
  86 {
  87         fprintf(stderr, "[%s] Received %s!\n", "process1", strsignal(signo));
  88
  89         if (signo == SIGUSR1) {
  90                 fprintf(stderr, "[%s] > Notified!\n", "process1");
  91                 struct queue_message msg;
  92                 /* Check queues from both other processes */
  93                 if (msgrcv(processes->pids[1], &msg, sizeof(int), 1, 0) > 0) {
  94                         fprintf(stderr, "[%s] > Notified with value: %s!\n", "process1", strsignal(msg.signo[0]));
  95                         raise(msg.signo[0]);
  96                         break;
  97                 }
  98                 else if (msgrcv(processes->pids[2], &msg, sizeof(int), 1, 0) > 0) {
  99                         fprintf(stderr, "[%s] > Notified with value: %s!\n", "process1", strsignal(msg.signo[0]));
 100                         raise(msg.signo[0]);
 101                         break;
 102                 }
 103         }
 104         else if (signo == SIGTERM) {
 105                 fprintf(stderr, "[%s] > Signalling other processes..\n", "process1");
 106                 processes->pids[1] = 0;
 107                 notify_other_processes(signo);
 108
 109                 fprintf(stderr, "[%s] > Releasing resources\n", "process1");
 110                 close(write_pipe);
 111                 unlink(write_pipe);
 112
 113                 if (buffer) {
 114                         free(buffer);
 115                         buffer = NULL;
 116                 }
 117                 exit(0);
 118         }
 119         else if (signo == SIGTSTP) {
 120                 fprintf(stderr, "[%s] > Closing pipe\n", "process1");
 121                 close(write_pipe);
 122                 raise (SIGSTOP);
 123         }
 124         else if (signo == SIGCONT) {
 125                 fprintf(stderr, "[%s] > Opening pipe\n", "process1");
 126                 file_descriptor = open(write_pipe, O_WRONLY);
 127         }
 128 }
 129
 130 /**
 131  * Program reads entire lines of text from the standard input and pass them
 132  * to the process2 using created pipe.
 133  */
 134 int main(void) {
 135         /** Currently fetched from stdin character */
 136         int c;
 137
 138         /** Current buffer length*/
 139         int buffer_length = 0;
 140
 141         /** Index of the current character */
 142         int i = 0;
 143
 144         /**
 145          * Temporary buffer used as a proxy between
 146          * checking memory allocation and copying data to real buffer
 147          */
 148         char * tmp = NULL;
 149
 150         fprintf(stderr, "[%s] Init!\n", "process1");
 151
 152         /**
 153          * Register signals handled by process
 154          */
 155         if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
 156                 fprintf(stderr, "can't catch SIGUSR1\n");
 157         }
 158         if (signal(SIGTERM, sig_handler) == SIG_ERR) {
 159                 fprintf(stderr, "can't catch SIGTERM\n");
 160         }
 161         if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
 162                 fprintf(stderr, "can't catch SIGTSTP\n");
 163         }
 164         if (signal(SIGCONT, sig_handler) == SIG_ERR) {
 165                 fprintf(stderr, "can't catch SIGCONT\n");
 166         }
 167
 168         /*
 169          * Register memory to share with other processes, and pass current
 170          * process id to the array.
 171          */
 172         shmid = shmget(shmkey, sizeof(struct message), IPC_CREAT | 0666);
 173
 174         processes = (struct message *)shmat(shmid, NULL, 0);
 175         processes->pids[0] = getpid();
 176
 177         fprintf(stderr, "[%s] Shared pid: %d\n", "process1", getpid());
 178
 179         /**
 180          * Register message queue to communicate with other processes
 181          */
 182         qkey = getpid();
 183         qid_input = msgget(qkey, IPC_CREAT | 0666);
 184
 185         qid_output1 = msgget(processes->pids[1], IPC_CREAT | 0666);
 186         qid_output2 = msgget(processes->pids[2], IPC_CREAT | 0666);
 187
 188         mkfifo(write_pipe, 0666);
 189
 190         file_descriptor = open(write_pipe, O_WRONLY);
 191
 192         do {
 193                 c = fgetc(stdin);
 194
 195                 /*
 196                  * Check if current index is bigger than current buffer size.
 197                  * If so increment buffer size. On error release memory, and set
 198                  * appropriate flags.
 199                  */
 200                 if (i >= buffer_length) {
 201                         tmp = NULL;
 202                         buffer_length += BUFFER_STEP;
 203                         tmp = (char*) realloc(buffer, buffer_length);
 204                         if (tmp == NULL) {
 205                                 fprintf(stderr, "[%s] Memory allocation problem on read!\n", "process1");
 206                                 free(buffer);
 207                                 buffer = NULL;
 208                                 c = EOF;
 209                         }
 210                 }
 211
 212                 /*
 213                  * If there were no errors or it was not just an empty newline:
 214                  * parse data.
 215                  */
 216                 if (c != EOF || ((i == 0) && (c == 10))) {
 217                         /* If newline has been found
 218                          * return entire string and release the memory
 219                          */
 220                         if (c == 10 && (i != 0)) {
 221                                 buffer[i] = '\n';
 222                                 write(file_descriptor, buffer, strlen(buffer));
 223                                 fprintf(stderr, "[%s] buffer: %s/%d\n", "process1", buffer, strlen(buffer));
 224
 225                                 buffer_length = 0;
 226                                 i = 0;
 227
 228                                 free(buffer);
 229                                 buffer = NULL;
 230                                 tmp = NULL;
 231                         }
 232                         /*
 233                          * Normal character, add it to the buffer
 234                          */
 235                         else {
 236                                 buffer = tmp;
 237                                 buffer[i] = c;
 238
 239                                 /* Used only for debugging..*/
 240                                 /*
 241                                 printf("c: %c/%d, i: %d, bl: %d\n", c, c, i, buffer_length);
 242                                 */
 243                                 i++;
 244                         }
 245                 }
 246         } while(c != EOF);
 247
 248         /* Release resources in normal program flow exit. */
 249         close(write_pipe);
 250         unlink(write_pipe);
 251
 252         if (buffer) {
 253                 free(buffer);
 254                 buffer = NULL;
 255         }
 256
 257         return 0;
 258 }