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

#define SIZE 20000

static void test(char *map, int fd, int line)
{
	unsigned char buf1[SIZE], buf2[SIZE];

	memcpy(buf1, map, SIZE);
	lseek(fd, 0, SEEK_SET);
	read(fd, buf2, SIZE);
	if (memcmp(buf1, buf2, SIZE) != 0) {
		int i;
		for (i=0;i<SIZE;i++) {
			if (buf1[i] != buf2[i]) {
				printf("mismatch at %d (%d %d)\n",
				       i, buf1[i], buf2[i]);
			}
		}
		printf("not equal on line %d!\n", line);
		exit(1);
	}
}

main()
{
	int fd;
	char *map;
	char b = 0;

	fd = open("test.dat", O_RDWR|O_CREAT|O_TRUNC, 0600);

	lseek(fd, SIZE-1, SEEK_SET);
	write(fd, &b, 1);

	map = mmap(NULL,SIZE,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_FILE, fd, 0);
	
	test(map, fd, __LINE__);

	map[3000] = 17;

	test(map, fd, __LINE__);

	lseek(fd, 76, SEEK_SET);
	write(fd, &fd, sizeof(fd));
	
	test(map, fd, __LINE__);
}