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

#define LEN		256
#define PRINT_STRIDE	0x20

static unsigned char data[LEN];
static unsigned char val = 0;

static unsigned char prev_data[LEN];

static unsigned char map_copy[LEN];

int main(int argc, char *argv[])
{
	unsigned long n;
	int h;
	unsigned char *map;
	unsigned start, end, i, j;
	unsigned int seed = 0;

	if (argc < 2) fprintf(stderr, "argc\n"), exit(1);
	h = open(argv[1], O_RDWR | O_DSYNC);
	if (h == -1) perror("open"), exit(1);
	map = mmap(NULL, LEN, PROT_READ | PROT_WRITE, MAP_SHARED, h, argc >= 3 ? strtoull(argv[2], NULL, 16) : 0);
	if (map == MAP_FAILED) perror("mmap"), exit(1);

	sleep(1);

rep:
	n = 0;
	srandom(seed);

	memset(data, 0, LEN);
	memset(prev_data, 0, LEN);
	memset(map, 0, LEN);

	while (1) {
		start = (unsigned)random() % LEN;
		end = (unsigned)random() % LEN;
		if (start > end)
			continue;
		for (i = start; i < end; i++)
			data[i] = val++;
		memcpy(map + start, data + start, end - start);
		/*usleep(10000);*/
		if (memcmp(map, data, LEN))
			break;
		memcpy(prev_data, data, LEN);
		n++;
	}

	memcpy(map_copy, map, LEN);
	fprintf(stderr, "mismatch after %lu loops! seed %u\n", n, seed);
	fprintf(stderr, "last copied range: 0x%x - 0x%x (0x%x)\n", start, end, (unsigned)(end - start));
	for (j = 0; j < LEN; j += PRINT_STRIDE) {
		fprintf(stderr, "p[%03x]", j);
		for (i = j; i < j + PRINT_STRIDE && i < LEN; i++)
			fprintf(stderr, "%s%s%02x", !(i % 4) ? " " : "", data[i] != map_copy[i] ? "*" : " ", prev_data[i]);
		fprintf(stderr, "\n");
		fprintf(stderr, "d[%03x]", j);
		for (i = j; i < j + PRINT_STRIDE && i < LEN; i++)
			fprintf(stderr, "%s%s%02x", !(i % 4) ? " " : "", data[i] != map_copy[i] ? "*" : " ", data[i]);
		fprintf(stderr, "\n");
		fprintf(stderr, "m[%03x]", j);
		for (i = j; i < j + PRINT_STRIDE && i < LEN; i++)
			fprintf(stderr, "%s%s%02x", !(i % 4) ? " " : "", data[i] != map_copy[i] ? "*" : " ", map_copy[i]);
		fprintf(stderr, "\n\n");
	}

	seed++;
	goto rep;
}