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#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <semaphore.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <fcntl.h>
#include "md5.h"
#include "utils.h"
static const char MY_NAME[] = "Mrs. Conclusion";
// Set up a Mrs. Premise & Mrs. Conclusion conversation.
int main() {
sem_t *the_semaphore = NULL;
int rc;
char s[1024];
int i;
int done;
int fd;
void *pSharedMemory = NULL;
char last_message_i_wrote[256];
char md5ified_message[256];
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.
the_semaphore = sem_open(params.semaphore_name, 0);
if (the_semaphore == SEM_FAILED) {
the_semaphore = NULL;
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
fd = shm_open(params.shared_memory_name, O_RDWR, params.permissions);
if (fd == -1) {
sprintf(s, "Couldn't get a handle to the shared memory; errno is %d", errno);
say(MY_NAME, s);
}
else {
// mmap it.
pSharedMemory = mmap((void *)0, (size_t)params.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (pSharedMemory == MAP_FAILED) {
sprintf(s, "MMapping the shared memory failed; errno is %d", errno);
say(MY_NAME, s);
}
else {
sprintf(s, "pSharedMemory = %p", pSharedMemory);
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, the_semaphore, params.live_dangerously);
if (rc)
done = 1;
else {
while ( (!rc) && \
(!strcmp((char *)pSharedMemory, last_message_i_wrote))
) {
// Nothing new; give Mrs. Premise another change to respond.
sprintf(s, "Read %zu characters '%s'", strlen((char *)pSharedMemory), (char *)pSharedMemory);
say(MY_NAME, s);
say(MY_NAME, "Releasing the semaphore");
rc = release_semaphore(MY_NAME, the_semaphore, params.live_dangerously);
if (!rc) {
say(MY_NAME, "Waiting to acquire the semaphore");
rc = acquire_semaphore(MY_NAME, the_semaphore, 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 *)pSharedMemory)) ) {
// All is well
i++;
if (i == params.iterations)
done = 1;
// MD5 the reply and write back to Mrs. Premise.
md5ify((char *)pSharedMemory, md5ified_message);
// Write back to Mrs. Premise.
sprintf(s, "Writing %zu characters '%s'", strlen(md5ified_message), md5ified_message);
say(MY_NAME, s);
strcpy((char *)pSharedMemory, 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 *)pSharedMemory, md5ified_message);
say(MY_NAME, s);
done = 1;
}
}
// Release the semaphore.
rc = release_semaphore(MY_NAME, the_semaphore, params.live_dangerously);
if (rc)
done = 1;
}
}
// Un-mmap the memory
rc = munmap(pSharedMemory, (size_t)params.size);
if (rc) {
sprintf(s, "Unmapping the memory failed; errno is %d", errno);
say(MY_NAME, s);
}
// Close the shared memory segment's file descriptor
if (-1 == close(fd)) {
sprintf(s, "Closing memory's file descriptor failed; errno is %d", errno);
say(MY_NAME, s);
}
}
rc = sem_close(the_semaphore);
if (rc) {
sprintf(s, "Closing the semaphore failed; errno is %d", errno);
say(MY_NAME, s);
}
}
return 0;
}
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