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
  54 /**
  55  * Unique key of message queue.
  56  */
  57 key_t qkey = 12356;
  58
  59 /**
  60  * Queue descriptor.
  61  */
  62 int qid;
  63
  64 /**
  65  * Structure holding queue message data.
  66  * Parameter mtype describes process to whom message is sent.
  67  * Parameter signo is a signal to raise after getting message.
  68  */
  69 struct queue_message {
  70         long mtype;
  71         int signo[1];
  72 };
  73
  74 void notify_other_processes(int signo) {
  75         int i = 0;
  76         struct queue_message msg;
  77         msg.signo[0] = signo;
  78
  79         for (; i < 3; i++) {
  80                 pid_t pid = processes->pids[i];
  81                 // Bleh
  82                 if (i != 0 && pid != 0) {
  83                         msg.mtype = i+1;
  84                         fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process1", msg.mtype, msg.signo[0]);
  85                         msgsnd(qid, &msg, sizeof(int), 0);
  86                         fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process1", strsignal(SIGUSR1), SIGUSR1, pid);
  87                         kill(pid, SIGUSR1);
  88                 }
  89         }
  90 }
  91
  92 /**
  93  * Handler for signals.
  94  */
  95 void sig_handler(int signo)
  96 {
  97         fprintf(stderr, "[%s] Received %s!\n", "process1", strsignal(signo));
  98         if (signo == SIGUSR1) {
  99                 fprintf(stderr, "[%s] > Notified!\n", "process1");
 100                 struct queue_message msg;
 101                 /* Check queues from both other processes */
 102                 if (msgrcv(qid, &msg, sizeof(int), 1, 0) > 0) {
 103                         fprintf(stderr, "[%s] > Notified with value: %s!\n", "process1", strsignal(msg.signo[0]));
 104                         raise(msg.signo[0]);
 105                 }
 106         }
 107         else if (signo == SIGTERM) {
 108                 fprintf(stderr, "[%s] > Signalling other processes..\n", "process1");
 109                 processes->pids[1] = 0;
 110                 notify_other_processes(signo);
 111
 112                 fprintf(stderr, "[%s] > Releasing resources\n", "process1");
 113                 close(write_pipe);
 114                 unlink(write_pipe);
 115
 116                 if (buffer) {
 117                         free(buffer);
 118                         buffer = NULL;
 119                 }
 120                 exit(0);
 121         }
 122         else if (signo == SIGTSTP) {
 123                 fprintf(stderr, "[%s] > Closing pipe\n", "process1");
 124                 close(write_pipe);
 125                 raise (SIGSTOP);
 126         }
 127         else if (signo == SIGCONT) {
 128                 fprintf(stderr, "[%s] > Opening pipe\n", "process1");
 129                 file_descriptor = open(write_pipe, O_WRONLY);
 130         }
 131 }
 132
 133 /**
 134  * Program reads entire lines of text from the standard input and pass them
 135  * to the process2 using created pipe.
 136  */
 137 int main(void) {
 138         /** Currently fetched from stdin character */
 139         int c;
 140
 141         /** Current buffer length*/
 142         int buffer_length = 0;
 143
 144         /** Index of the current character */
 145         int i = 0;
 146
 147         /**
 148          * Temporary buffer used as a proxy between
 149          * checking memory allocation and copying data to real buffer
 150          */
 151         char * tmp = NULL;
 152
 153         fprintf(stderr, "[%s] Init!\n", "process1");
 154
 155         /**
 156          * Register signals handled by process
 157          */
 158         if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
 159                 fprintf(stderr, "can't catch SIGUSR1\n");
 160         }
 161         if (signal(SIGTERM, sig_handler) == SIG_ERR) {
 162                 fprintf(stderr, "can't catch SIGTERM\n");
 163         }
 164         if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
 165                 fprintf(stderr, "can't catch SIGTSTP\n");
 166         }
 167         if (signal(SIGCONT, sig_handler) == SIG_ERR) {
 168                 fprintf(stderr, "can't catch SIGCONT\n");
 169         }
 170
 171         /*
 172          * Register memory to share with other processes, and pass current
 173          * process id to the array.
 174          */
 175         shmid = shmget(shmkey, sizeof(struct message), IPC_CREAT | 0666);
 176
 177         processes = (struct message *)shmat(shmid, NULL, 0);
 178         processes->pids[0] = getpid();
 179
 180         fprintf(stderr, "[%s] Shared pid: %d\n", "process1", getpid());
 181
 182         /**
 183          * Register message queue to communicate with other processes
 184          */
 185         qid = msgget(qkey, IPC_CREAT | 0666);
 186
 187         mkfifo(write_pipe, 0666);
 188
 189         file_descriptor = open(write_pipe, O_WRONLY);
 190
 191         do {
 192                 c = fgetc(stdin);
 193
 194                 /*
 195                  * Check if current index is bigger than current buffer size.
 196                  * If so increment buffer size. On error release memory, and set
 197                  * appropriate flags.
 198                  */
 199                 if (i >= buffer_length) {
 200                         tmp = NULL;
 201                         buffer_length += BUFFER_STEP;
 202                         tmp = (char*) realloc(buffer, buffer_length);
 203                         if (tmp == NULL) {
 204                                 fprintf(stderr, "[%s] Memory allocation problem on read!\n", "process1");
 205                                 free(buffer);
 206                                 buffer = NULL;
 207                                 c = EOF;
 208                         }
 209                 }
 210
 211                 /*
 212                  * If there were no errors or it was not just an empty newline:
 213                  * parse data.
 214                  */
 215                 if (c != EOF || ((i == 0) && (c == 10))) {
 216                         /* If newline has been found
 217                          * return entire string and release the memory
 218                          */
 219                         if (c == 10 && (i != 0)) {
 220                                 buffer[i] = '\n';
 221                                 write(file_descriptor, buffer, strlen(buffer));
 222                                 fprintf(stderr, "[%s] buffer: %s/%d\n", "process1", buffer, strlen(buffer));
 223
 224                                 buffer_length = 0;
 225                                 i = 0;
 226
 227                                 free(buffer);
 228                                 buffer = NULL;
 229                                 tmp = NULL;
 230                         }
 231                         /*
 232                          * Normal character, add it to the buffer
 233                          */
 234                         else {
 235                                 buffer = tmp;
 236                                 buffer[i] = c;
 237
 238                                 /* Used only for debugging..*/
 239                                 /*
 240                                 printf("c: %c/%d, i: %d, bl: %d\n", c, c, i, buffer_length);
 241                                 */
 242                                 i++;
 243                         }
 244                 }
 245         } while(c != EOF);
 246
 247         /* Release resources in normal program flow exit. */
 248         close(write_pipe);
 249         unlink(write_pipe);
 250
 251         if (buffer) {
 252                 free(buffer);
 253                 buffer = NULL;
 254         }
 255
 256         return 0;
 257 }