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#include <sys/ipc.h> /* for system's IPC_xxx definitions */
#include <sys/shm.h> /* for shmget, shmat, shmdt, shmctl */
#include <sys/sem.h> /* for semget, semctl, semop */
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include "md5.h"
#include "utils.h"
static const char MY_NAME[] = "Mrs. Conclusion";
// Set up a Mrs. Premise & Mrs. Conclusion conversation.
int main() {
int sem_id = 0;
int shm_id = 0;
int rc;
char s[1024];
int i;
int done;
char last_message_i_wrote[256];
char md5ified_message[256];
void *address = NULL;
struct param_struct params;
say(MY_NAME, "Oooo 'ello, I'm Mrs. Conclusion!");
read_params(¶ms);
// Mrs. Premise has already created the semaphore and shared memory.
// I just need to get handles to them.
sem_id = semget(params.key, 0, params.permissions);
if (-1 == sem_id) {
sem_id = 0;
sprintf(s, "Getting a handle to the semaphore failed; errno is %d", errno);
say(MY_NAME, s);
}
else {
// get a handle to the shared memory
shm_id = shmget(params.key, params.size, params.permissions);
if (shm_id == -1) {
shm_id = 0;
sprintf(s, "Couldn't get a handle to the shared memory; errno is %d", errno);
say(MY_NAME, s);
}
else {
sprintf(s, "Shared memory's id is %d", shm_id);
say(MY_NAME, s);
// Attach the memory.
address = shmat(shm_id, NULL, 0);
if ((void *)-1 == address) {
address = NULL;
sprintf(s, "Attaching the shared memory failed; errno is %d", errno);
say(MY_NAME, s);
}
else {
sprintf(s, "shared memory address = %p", address);
say(MY_NAME, s);
i = 0;
done = 0;
last_message_i_wrote[0] = '\0';
while (!done) {
sprintf(s, "iteration %d", i);
say(MY_NAME, s);
// Wait for Mrs. Premise to free up the semaphore.
rc = acquire_semaphore(MY_NAME, sem_id, params.live_dangerously);
if (rc)
done = 1;
else {
while ( (!rc) && \
(!strcmp((char *)address, last_message_i_wrote))
) {
// Nothing new; give Mrs. Premise another change to respond.
sprintf(s, "Read %zu characters '%s'", strlen((char *)address), (char *)address);
say(MY_NAME, s);
rc = release_semaphore(MY_NAME, sem_id, params.live_dangerously);
if (!rc) {
rc = acquire_semaphore(MY_NAME, sem_id, params.live_dangerously);
}
}
md5ify(last_message_i_wrote, md5ified_message);
// I always accept the first message (when i == 0)
if ( (i == 0) || (!strcmp(md5ified_message, (char *)address)) ) {
// All is well
i++;
if (i == params.iterations)
done = 1;
// MD5 the reply and write back to Mrs. Premise.
md5ify((char *)address, md5ified_message);
// Write back to Mrs. Premise.
sprintf(s, "Writing %zu characters '%s'", strlen(md5ified_message), md5ified_message);
say(MY_NAME, s);
strcpy((char *)address, md5ified_message);
strcpy(last_message_i_wrote, md5ified_message);
}
else {
sprintf(s, "Shared memory corruption after %d iterations.", i);
say(MY_NAME, s);
sprintf(s, "Mismatch; rc = %d, new message is '%s', expected '%s'.", rc, (char *)address, md5ified_message);
say(MY_NAME, s);
done = 1;
}
}
// Release the semaphore.
rc = release_semaphore(MY_NAME, sem_id, params.live_dangerously);
if (rc)
done = 1;
}
if (-1 == shmdt(address)) {
sprintf(s, "Detaching the memory failed; errno is %d", errno);
say(MY_NAME, s);
}
address = NULL;
}
}
}
return 0;
}
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