#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <time.h>

#define PATH_MAX	4096

int main(int argc, char *argv[])
{
	unsigned int iter;
	unsigned long o_read_ms, o_write_ms, o_time_ms;
	char path[PATH_MAX];
	int fd;

	if (argc != 2) {
		printf("Usage: %s <bdev>\n", argv[0]);
		exit(0);
	}

	if (!snprintf(path, PATH_MAX, "/sys/block/%s/stat", argv[1]))
		fprintf(stderr, "Could not build path\n"), exit(1);

	iter = 0;
	for (;;) {
		unsigned long d_read_ms, d_write_ms, d_time_ms;
		unsigned long read_ms, write_ms, time_ms;
		
		struct timeval tv;
		int ret;
		char *token;
		char mem[1024];

		fd = open(path, O_RDONLY);
		if (fd == -1)
			perror("open"), exit(1);

		if (gettimeofday(&tv, NULL) == -1)
			perror("gettimeofday"), exit(1);
		
		time_ms = tv.tv_sec * 1000 + tv.tv_usec / 1000;
		d_time_ms = time_ms - o_time_ms;
		
		do {
			ret = read(fd, mem, 1024);
		} while (ret == -1 && errno == EINTR);
		if (ret == -1)
			perror("read"), exit(1);
		if (close(fd) == -1)
			perror("close"), exit(1);

		strtok(mem, " ");
		strtok(NULL, " ");
		strtok(NULL, " ");
		token = strtok(NULL, " ");
		if (!token)
			fprintf(stderr, "strtok failed\n"), exit(1);
		errno = 0;
		read_ms = strtoul(token, NULL, 10);
		if (errno == ERANGE)
			fprintf(stderr, "strtoul failed\n"), exit(1);

		strtok(NULL, " ");
		strtok(NULL, " ");
		strtok(NULL, " ");
		token = strtok(NULL, " ");
		if (!token)
			fprintf(stderr, "strtok failed\n"), exit(1);
		errno = 0;
		write_ms = strtoul(token, NULL, 10);
		if (errno == ERANGE)
			fprintf(stderr, "strtoul failed\n"), exit(1);
	
		d_read_ms = read_ms - o_read_ms;
		d_write_ms = write_ms - o_write_ms;
		if (d_read_ms + d_write_ms > d_time_ms)
			d_time_ms = d_read_ms + d_write_ms;

		if (iter % 20 == 0)
			printf("bdev\t  bi %%\t  bo %%\t  io %%\t  id %%\n");

		if (iter && d_time_ms) {
			printf("%s\t%6.1f\t%6.1f\t%6.1f\t%6.1f\n",
			argv[1],
			100.0f * d_read_ms / d_time_ms,
			100.0f * d_write_ms / d_time_ms,
			100.0f * (d_read_ms + d_write_ms) / d_time_ms,
			100.0f - 100.0f * (d_read_ms | d_write_ms) / d_time_ms);
		}

		o_read_ms = read_ms;
		o_write_ms = write_ms;
		o_time_ms = time_ms;

		sleep(1);
		iter++;
	}
	
	return 0;
}