#include        <unistd.h>
#include	<errno.h>
#include	<stdio.h>
#include	<fcntl.h>
#include	<signal.h>
#include	<sys/mman.h>
#include	<stdlib.h>

#define	usage()	\
	printf("Usage: %s [-F filename] [-M freememory] \
		[-P percentage_of_occupation] \n",argv[0]); \
	exit(1);


void signal_handler(int signal);

/*
 * Define command line args
 */
extern int optind;
extern int optopt;
extern int opterr;
extern char *optarg;

int 		fd; /* FILE *fd */
static int 	F_flag, M_flag, P_flag = 0;
size_t 		length;
caddr_t		map;
char		*filename;

int main(int argc, char **argv)
{
	int opt;
	struct sigaction generic_sigaction;
	ulong freemem;
	double percent;
	pid_t pid;

	while ((opt = getopt(argc, argv, "M:P:F:")) != EOF)
	{
		switch (opt)
		{
		case 'F':	/* give a filename to be mapped*/
			F_flag++;
			filename = optarg;
		case 'M':	/* free memory */
			M_flag++;
			freemem = atol(optarg);
			break;
		case 'P':	/* allocate to a % of free memory */
			P_flag++;
			percent = atof(optarg);
			break;
		default:
			usage();
			break;
		}
	}
	
	if (P_flag)
	{
		if (percent>=100)
			percent/=100;
		length=freemem*percent;
	}
	else 
	{
		length = freemem*0.90;
		/* by default 90% of the free memory will be occupied */
	}
	if (!F_flag)
	{
		usage();
	}

	file_create(length);	
	
	if ((map = mmap(NULL, length, PROT_WRITE | PROT_READ, 
		MAP_FILE | MAP_SHARED, fd, 0)) == (caddr_t) -1)
	{
		perror(" mmap failed ");
		cleanup(-1);
	} 
	pid = fork();
	if (pid == (pid_t) -1)
	{
		perror("fork failed");
		cleanup(-1);
	}
	else if (pid != 0)
	{
		close(fd);
		exit(0);
	}
	sleep(2);

	generic_sigaction.sa_handler = signal_handler;
	sigfillset(&generic_sigaction.sa_mask);
	generic_sigaction.sa_flags = 0;
	sigaction(SIGINT, &generic_sigaction, NULL); 
	sigaction(SIGSEGV, &generic_sigaction, NULL); 
	sigaction(SIGBUS, &generic_sigaction, NULL); 
	while (1) {}
	cleanup(0);
}


void signal_handler(int signal)
{	
	munmap(map, length);
	cleanup(1);
}
cleanup(int code)
{
	close(fd);
	remove(filename);
	exit(code);

}
file_create(ulong size)
{
ulong i;
    if ((fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0700)) != -1 )
    {
        for (i=0; i<(size/10); i++)
	{
		write(fd, "0123456789", 10);
	}
	for (i=0; i<(size%10); i++)
	{
		write(fd, "1", 1);
	}
	fsync(fd);
	return(fd);
    }
    else
    {
	perror("open failed");
	return(-1);
    }
}