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#include <stdio.h> /* printf() */
#include <stddef.h> /* sizeof() */
#include <signal.h> /* signal(), SIGINT */
#include <sys/mman.h> /* PROT_READ, needed for rtai_shm.h */
#include <sys/types.h> /* off_t, needed for rtai_shm.h */
#include <sys/fcntl.h> /* O_RDWR, needed for rtai_shm.h */
#include <rtai_shm.h> /* rtai_malloc,free() */
#include "common.h" /* SHM_KEY, SHM_HOWMANY */
/*
This signal handler just sets the 'done' flag, which we will loop
on when printing the shared memory. This lets us quit nicely.
*/
static int done = 0;
static void quit(int sig)
{
done = 1;
}
int main(void)
{
int * shm_array;
int head, tail;
shm_array = rtai_malloc(SHM_KEY, SHM_HOWMANY * sizeof(int));
if (0 == shm_array) {
fprintf(stderr, "can't allocate shared memory\n");
return 1;
}
/*
Attach our signal hander to SIGINT, the signal raised when we hit
Control-C.
*/
signal(SIGINT, quit);
while (! done) {
/*
Read the first and last element of the array. The should be
the same, but if we are interrupted by the RT code in between
these reads, the tail will be newer.
*/
head = shm_array[0];
/* we could get interrupted here */
tail = shm_array[SHM_HOWMANY - 1];
/*
Print out head and tail of shared memory, and an error if
they're different.
*/
printf("%10d\t%10d\r", head, tail);
if (head != tail) {
printf("\nsplit read\n");
}
}
/*
Control-C stopped us, so let's exit nicely by freeing up our connection
to shared memory.
*/
rtai_free(SHM_KEY, shm_array);
return 0;
}
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