#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/mman.h>

#define MMAP_FILE "mmap-test-file"
#define MMAP_SIZE 16384*1024

main()
{
	int fd;
	char* maddr;

	printf("creating " MMAP_FILE "\n");
	fd = open(MMAP_FILE, O_CREAT|O_TRUNC|O_RDWR, 0666);
	if(fd < 0)
	{
		perror("Could not open " MMAP_FILE);
		exit(1);
	}

	printf("Writing zeros\n");
	{
		int n = MMAP_SIZE;
		char buf[1024];
		memset(buf, 0, 1024);
		while(n > 0)
		{
			write(fd, buf, 1024);
			n -= 1024;
		}
	}
	
	printf("mmap-ing\n");
	maddr = mmap(NULL, MMAP_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if(maddr == NULL || maddr == MAP_FAILED)
	{
		perror("mmap");
		exit(1);
	}

	printf("writing ones to mmap region\n");
	{
		int n;
		for(n = 0; n < MMAP_SIZE; n++)	
			maddr[n] = 1;
	}

	printf("done!\n");
}