#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/auxv.h>
#include <unistd.h>
#include <fcntl.h>
#include <err.h>

int main(int argc, char **argv)
{
	if (argc < 2)
		errx(EXIT_FAILURE, "expected file name");

	const char *filename = argv[1];
	int fd = open(filename, O_RDONLY);
	if (fd < 0)
		err(EXIT_FAILURE, "open");

	struct stat fst = {0};
	if (fstat(fd, &fst) < 0)
		err(EXIT_FAILURE, "fstat");

	const size_t filesize = fst.st_size;
	uint8_t *filem = mmap(NULL, filesize, PROT_READ, MAP_PRIVATE, fd, 0);
	if (filem == MAP_FAILED)
		err(EXIT_FAILURE, "mmap failed");
	/* we can close the descriptor now */
	close(fd);

	unsigned int seed = 0;
	memcpy(&seed, (void *)getauxval(AT_RANDOM), sizeof(seed));
	srand(seed);

	const size_t off = abs(rand()) % filesize;
	uint8_t pb = 0, cb;
	size_t cbo = 0;
	for (size_t i = off; i < off + 0xff && i < filesize; ++i) {
		cb = filem[i];
		if (cb == pb)
			++cbo;
		if (cbo == 16) {
			printf("* ");
			cbo = 0;
		} else
			printf("%x ", cb);
		pb = cb;
	}
	putchar('\n');

	munmap(filem, filesize);
	return 0;
}