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[0] = 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] > Signalling other processes..\n", "process1");
 124                 processes->pids[0] = 0;
 125                 notify_other_processes(signo);
 126 //              sleep(1);
 127                 processes->pids[0] = getpid();
 128
 129                 fprintf(stderr, "[%s] > Closing pipe\n", "process1");
 130                 close(write_pipe);
 131                 raise (SIGSTOP);
 132         }
 133         else if (signo == SIGCONT) {
 134                 fprintf(stderr, "[%s] > Opening pipe\n", "process1");
 135                 file_descriptor = open(write_pipe, O_WRONLY);
 136                 processes->pids[0] = 0;
 137                 notify_other_processes(signo);
 138 //              sleep(1);
 139                 processes->pids[0] = getpid();
 140         }
 141 }
 142
 143 /**
 144  * Program reads entire lines of text from the standard input and pass them
 145  * to the process2 using created pipe.
 146  */
 147 int main(void) {
 148         /** Currently fetched from stdin character */
 149         int c;
 150
 151         /** Current buffer length*/
 152         int buffer_length = 0;
 153
 154         /** Index of the current character */
 155         int i = 0;
 156
 157         /**
 158          * Temporary buffer used as a proxy between
 159          * checking memory allocation and copying data to real buffer
 160          */
 161         char * tmp = NULL;
 162
 163         fprintf(stderr, "[%s] Init!\n", "process1");
 164
 165         /**
 166          * Register signals handled by process
 167          */
 168         if (signal(SIGUSR1, sig_handler) == SIG_ERR) {
 169                 fprintf(stderr, "can't catch SIGUSR1\n");
 170         }
 171         if (signal(SIGTERM, sig_handler) == SIG_ERR) {
 172                 fprintf(stderr, "can't catch SIGTERM\n");
 173         }
 174         if (signal(SIGTSTP, sig_handler) == SIG_ERR) {
 175                 fprintf(stderr, "can't catch SIGTSTP\n");
 176         }
 177         if (signal(SIGCONT, sig_handler) == SIG_ERR) {
 178                 fprintf(stderr, "can't catch SIGCONT\n");
 179         }
 180
 181         /*
 182          * Register memory to share with other processes, and pass current
 183          * process id to the array.
 184          */
 185         shmid = shmget(shmkey, sizeof(struct message), IPC_CREAT | 0666);
 186
 187         processes = (struct message *)shmat(shmid, NULL, 0);
 188         processes->pids[0] = getpid();
 189
 190         fprintf(stderr, "[%s] Shared pid: %d\n", "process1", getpid());
 191
 192         /**
 193          * Register message queue to communicate with other processes
 194          */
 195         qid = msgget(qkey, IPC_CREAT | 0666);
 196
 197         mkfifo(write_pipe, 0666);
 198
 199         file_descriptor = open(write_pipe, O_WRONLY);
 200
 201         do {
 202                 c = fgetc(stdin);
 203
 204                 /*
 205                  * Check if current index is bigger than current buffer size.
 206                  * If so increment buffer size. On error release memory, and set
 207                  * appropriate flags.
 208                  */
 209                 if (i >= buffer_length) {
 210                         tmp = NULL;
 211                         buffer_length += BUFFER_STEP;
 212                         tmp = (char*) realloc(buffer, buffer_length);
 213                         if (tmp == NULL) {
 214                                 fprintf(stderr, "[%s] Memory allocation problem on read!\n", "process1");
 215                                 free(buffer);
 216                                 buffer = NULL;
 217                                 c = EOF;
 218                         }
 219                 }
 220
 221                 /*
 222                  * If there were no errors or it was not just an empty newline:
 223                  * parse data.
 224                  */
 225                 if (c != EOF || ((i == 0) && (c == 10))) {
 226                         /* If newline has been found
 227                          * return entire string and release the memory
 228                          */
 229                         if (c == 10 && (i != 0)) {
 230                                 buffer[i] = '\n';
 231                                 write(file_descriptor, buffer, strlen(buffer));
 232                                 fprintf(stderr, "[%s] buffer: %s/%d\n", "process1", buffer, strlen(buffer));
 233
 234                                 buffer_length = 0;
 235                                 i = 0;
 236
 237                                 free(buffer);
 238                                 buffer = NULL;
 239                                 tmp = NULL;
 240                         }
 241                         /*
 242                          * Normal character, add it to the buffer
 243                          */
 244                         else {
 245                                 buffer = tmp;
 246                                 buffer[i] = c;
 247
 248                                 /* Used only for debugging..*/
 249                                 /*
 250                                 printf("c: %c/%d, i: %d, bl: %d\n", c, c, i, buffer_length);
 251                                 */
 252                                 i++;
 253                         }
 254                 }
 255         } while(c != EOF);
 256
 257         /* Release resources in normal program flow exit. */
 258         close(write_pipe);
 259         unlink(write_pipe);
 260
 261         if (buffer) {
 262                 free(buffer);
 263                 buffer = NULL;
 264         }
 265
 266         return 0;
 267 }