#define _GNU_SOURCE
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <linux/fs.h>

#define BUFSIZE (8*1024*1024ul)

static unsigned int maxbuf = ~0U;
static int do_fadvise;

static void parse_opt(int argc, char **argv)
{
	int ch;

	while (1) {
		ch = getopt(argc, argv, "fb:");
		if (ch == -1)
			break;

		switch (ch) {
		case 'f':
			do_fadvise = 1;
			fprintf(stderr, "using fadvise()\n");
			break;
		case 'b':
			if (atoi(optarg) > 1)
				maxbuf = atoi(optarg);
			else
				fprintf(stderr, "invalid bufcount '%s'\n",
					optarg);
			break;
		default:
			fprintf(stderr, "invalid option 0%o (%c)\n",
				ch,
				isprint(ch) ? ch : '-');
			break;
		}
	}
}

int main(int argc, char **argv)
{
	static char buffer[BUFSIZE];
	struct timeval start, now;
	unsigned int index;
	int fd;

	parse_opt(argc, argv);

	mlockall(MCL_CURRENT | MCL_FUTURE);
	fd = open("/dev/urandom", O_RDONLY);
	if (read(fd, buffer, BUFSIZE) != BUFSIZE) {
		perror("/dev/urandom");
		exit(1);
	}
	close(fd);

	fd = open(argv[optind], O_RDWR | O_CREAT, 0666);
	if (fd < 0) {
		perror(argv[optind]);
		exit(1);
	}

	if (maxbuf != ~0U)
		fprintf(stderr, "writing %u buffers of size %lum\n",
			maxbuf, BUFSIZE / (1024 * 1024ul));

	gettimeofday(&start, NULL);
	for (index = 0; index < maxbuf; index++) {
		double s;
		unsigned long MBps;
		unsigned long MB;

		if (write(fd, buffer, BUFSIZE) != BUFSIZE)
			break;
		sync_file_range(fd, index*BUFSIZE, BUFSIZE, SYNC_FILE_RANGE_WRITE);
		if (index)
			sync_file_range(fd, (index-1)*BUFSIZE, BUFSIZE, SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER);
		if (do_fadvise)
			posix_fadvise(fd, (index-1)*BUFSIZE, BUFSIZE,
				      POSIX_FADV_DONTNEED);
		gettimeofday(&now, NULL);
		s = (now.tv_sec - start.tv_sec) + ((double) now.tv_usec - start.tv_usec)/ 1000000;

		MB = index * (BUFSIZE >> 20);
		MBps = MB;
		if (s > 1)
			MBps = MBps / s;
		printf("%8lu.%03lu GB written in %5.2f (%lu MB/s)           \r",
			MB >> 10, (MB & 1023) * 1000 >> 10, s, MBps);
		fflush(stdout);
	}
	close(fd);
	printf("\n");
	return 0;
}