#include <sys/ioctl.h>
#include <sys/disk.h>
#include <sys/types.h>
#include <sys/uio.h>

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <time.h>
#include <string.h>
#include <err.h>
#include <unistd.h>

#define SECTORSIZE 512
#define READSIZE 512*20000*10
#define SMALLREADSIZE 512
#define NSEC_IN_SEC 1000000000UL
#define NSEC_IN_MSEC 1000000UL

void
measure_one(int fd, off_t off)
{
	struct timespec tstart, tend;
	char buf[READSIZE];

	if (lseek(fd, off, SEEK_SET) < 0)
		err(1, "lseek");
	if (clock_gettime(CLOCK_MONOTONIC, &tstart) != 0)
		err(1, "clock_gettime");
	if (write(fd, buf, READSIZE) < 0)
		err(1, "read");
	if (clock_gettime(CLOCK_MONOTONIC, &tend) != 0)
		err(1, "clock_gettime");

	printf("off %lld: %lu ns\n", off,
	    (((long)tend.tv_sec * NSEC_IN_SEC +  tend.tv_nsec)
	    - ((long)tstart.tv_sec * NSEC_IN_SEC + tstart.tv_nsec)));
}

void
measure_seek(int fd, off_t start, off_t end)
{
	struct timespec tstart, tend;
	char buf[READSIZE];
	int i;

#if 0
	/* Try to flush the cache by doing large reads in the middle */
	if (lseek(fd, (end - start) / 2, SEEK_SET) < 0)
		err(1, "lseek");
	for (i = 0; i < 15; i++) {
		if (lseek(fd, (end - start) / 2, SEEK_SET) < 0)
			err(1, "lseek");
		if (read(fd, buf, READSIZE) < 0)
			err(1, "read");
	}
#endif
	
	if (lseek(fd, start, SEEK_SET) < 0)
		err(1, "lseek");
	if (write(fd, buf, SMALLREADSIZE) < 0)
			err(1, "read");
	if (lseek(fd, end - SMALLREADSIZE, SEEK_SET) < 0)
		err(1, "lseek");
	if (clock_gettime(CLOCK_MONOTONIC, &tstart) != 0)
		err(1, "clock_gettime");
	if (write(fd, buf, SMALLREADSIZE) < 0)
		err(1, "read");
	if (clock_gettime(CLOCK_MONOTONIC, &tend) != 0)
		err(1, "clock_gettime");

	printf("distance %lld %lu ns\n", end - start, 
	    (((long)tend.tv_sec * NSEC_IN_SEC +  tend.tv_nsec)
	    - ((long)tstart.tv_sec * NSEC_IN_SEC + tstart.tv_nsec)));
}

void
measure_seek2(int fd, off_t start, off_t end)
{
	struct timespec tstart, tend;
	char buf[READSIZE];
	off_t i, pos;

	if (lseek(fd, start, SEEK_SET) < 0)
		err(1, "lseek");
	if (write(fd, buf, SMALLREADSIZE) < 0)
			err(1, "read");

	for (i = 0;; i++) {
		if ((pos = lseek(fd, i * SMALLREADSIZE, SEEK_CUR)) < 0)
			err(1, "lseek");
		if (pos > end)
			break;
		printf("pos %lld\n", pos);
		if (clock_gettime(CLOCK_MONOTONIC, &tstart) != 0)
			err(1, "clock_gettime");
		if (write(fd, buf, SMALLREADSIZE) < 0)
			err(1, "read");
		if (clock_gettime(CLOCK_MONOTONIC, &tend) != 0)
			err(1, "clock_gettime");
		printf("distance2 %lld %lu ns\n", i * SMALLREADSIZE, 
		    (((long)tend.tv_sec * NSEC_IN_SEC +  tend.tv_nsec)
		    - ((long)tstart.tv_sec * NSEC_IN_SEC + tstart.tv_nsec)));
	}
}

int
main(int argc, char **argv)
{
	off_t mediasize, i;
	int fd, j, stride;

	if (argc < 4) {
		printf("Usage: %s <command> <path> <stride>\n", argv[0]);
		exit(1);
	}

	stride = atoi(argv[3]);

	if ((fd = open(argv[2], O_RDWR | O_DIRECT)) < 0)
		err(1, "open");

	if (ioctl(fd, DIOCGMEDIASIZE, &mediasize) != 0)
		err(1, "ioctl(DIOCMEDIASIZE)");

	if (strcmp("stride", argv[1]) == 0) {
		printf("%lld blocks stride %d\n", mediasize / SECTORSIZE,
		    stride);
		for (i = 0; i < mediasize / SECTORSIZE; i += stride)
			measure_one(fd, i * SECTORSIZE);
		return (0);
	} if (strcmp("seek2", argv[1]) == 0) {
		printf("seek2\n");
		measure_seek2(fd, 0, mediasize);
		return (0);
	}

	for (i = 0; i < mediasize; i += READSIZE)
		for (j = 0; j < 5; j++)
			measure_seek(fd, 0, mediasize - i);

	return (0);
}