#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <errno.h>
#include <time.h>

static char *argv0;

static char *get_this_name(void)
{
	static char *this_name;
	char *arg;
	char *p;

	if (this_name)
		return this_name;

	arg = argv0;
	p = arg+strlen(arg);

	while (p >= arg && *p != '/')
		p--;
	p++;

	this_name = p;
	return p;
}

static void usage(void)
{
	char *p = get_this_name();

	printf("usage: %s [alignement]\n"
	       "  alignment is a number offset\n"
	       "\n",p);
	exit(-1);
}

static void __vdie(const char *fmt, va_list ap, int err)
{
	int ret = errno;
	char *p = get_this_name();

	if (err && errno)
		perror(p);
	else
		ret = -1;

	fprintf(stderr, "  ");
	vfprintf(stderr, fmt, ap);

	fprintf(stderr, "\n");
	exit(ret);
}

void die(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	__vdie(fmt, ap, 0);
	va_end(ap);
}

void pdie(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	__vdie(fmt, ap, 1);
	va_end(ap);
}

static unsigned long long get_time(void)
{
	unsigned long long time;
	struct timespec ts;

	clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
	time = ts.tv_sec * 1000000;
	time += ts.tv_nsec / 1000;

	return time;
}

#define ARRAY_SIZE 1000000

static void fill_array(void *array)
{
	for (int i = 0; i < ARRAY_SIZE; i++) {
		*(long *)(array + sizeof(long) * i) = i;
	}
}

int main (int argc, char **argv)
{
	unsigned long long start, end;
	unsigned long long val = 0;
	unsigned long long idx, i;
	void *array;
	int offset;

	argv0 = argv[0];

	if (argc < 2)
		usage();

	array = malloc((ARRAY_SIZE + 1) * sizeof(long));
	if (!array)
		pdie("Allocating array");

	fill_array(array);

	offset = atoi(argv[1]);

	start = get_time();
	for (i = 0; i < ARRAY_SIZE; i++) {
		idx = (i * 5618) + offset;
		idx %= 1000000;
		val += *(unsigned long *)(array + idx);
	}
	end = get_time();

	printf("val = %lld\n", val);
	printf("time = %lld us\n", end - start);
	
	return 0;
}