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Diffstat (limited to 'demo/conclusion.c')
| -rw-r--r-- | demo/conclusion.c | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/demo/conclusion.c b/demo/conclusion.c new file mode 100644 index 0000000..7b10aef --- /dev/null +++ b/demo/conclusion.c @@ -0,0 +1,139 @@ +#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; +} |