#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define MAP_SIZE 32
#define TEST_FILE "textfile.txt" 

// TEST_FILE must be larger than a (16 * pagesize) + 32 bytes

int main(int argc, char **argv) {

	int fd, offset;
	void * startAddr;

	fd = open(TEST_FILE, O_RDONLY);

	/* map with non-zero offset */
	offset = 0;
	startAddr = mmap(0, MAP_SIZE, PROT_READ, MAP_SHARED, fd, offset);
	printf("Mapped file with zero offset at %d\n", (int)startAddr);
	printf("%c\n", *((char *)startAddr));	
	munmap(startAddr, MAP_SIZE); 

	/* map with non-zero offset */
	offset = 16 * getpagesize();
	startAddr = mmap(0, MAP_SIZE, PROT_READ, MAP_SHARED, fd, offset);
	printf("Mapped file with nonzero offset at %d\n", (int)startAddr);
	printf("%c\n", *((char *)startAddr));
	munmap(startAddr, MAP_SIZE); 

	close(fd);
	
	return 0;
}