#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <time.h>
#include <sys/select.h>
#include <fcntl.h>
#include <errno.h>

#define BLKSIZ 16384
#define NBLK (100*(1<<20)/BLKSIZ)

int main()
{
	int fd[2];
	pid_t pid;
	int nonblock = 1;

	pipe(fd);

	if (!(pid = fork ())) {
		int i;
		char buf[BLKSIZ] = {0,};
		close(fd[0]);
		if (nonblock) {
			int flags;
			flags = fcntl(fd[1], F_GETFL);
			flags |= O_NONBLOCK;
			fcntl(fd[1], F_SETFL, flags);
		}
		fd_set wfds;
		for (i=0; i<NBLK; i++) {
			FD_ZERO(&wfds);
			FD_SET(fd[1], &wfds);
			if (select(fd[1]+1, NULL, &wfds, NULL, NULL) > 0
					&& FD_ISSET(fd[1], &wfds)) {
				ssize_t len = write(fd[1], buf, sizeof(buf));
				if (len <= 0 && errno == EAGAIN) printf("w", i);
				if (len <= 0 && errno == EAGAIN) i --;
			}
		}
		close(fd[1]);
	} else {
		int i;
		char buf[BLKSIZ] = {0,};
		int total = 0;
		fd_set rfds;
		struct timespec tv0, tv1;
		double elasped;
		close(fd[1]);
		if (nonblock) {
			int flags;
			flags = fcntl(fd[0], F_GETFL);
			flags |= O_NONBLOCK;
			fcntl(fd[0], F_SETFL, flags);
		}
		usleep(100000); /* Delay to start reader */
		clock_gettime(CLOCK_MONOTONIC, &tv0);
		for (i=0; i<NBLK; i++) {
			FD_ZERO(&rfds);
			FD_SET(fd[0], &rfds);
			if (select(fd[0]+1, &rfds, NULL, NULL, NULL) > 0
					&& FD_ISSET(fd[0], &rfds)) {
				ssize_t len = read(fd[0], buf, sizeof(buf));
				if (len <= 0 && errno == EAGAIN) printf("r");
				if (len <= 0 && errno == EAGAIN) i --;
				else if(len < 0) break;
				else total += len;
			}
		}
		clock_gettime(CLOCK_MONOTONIC, &tv1);
		close(fd[0]);
		elasped = (tv1.tv_sec - tv0.tv_sec) + (tv1.tv_nsec - tv0.tv_nsec)*1e-9;
		printf("Total: %dMB in %f second, %fMB/s\n",
			total/(1<<20), elasped, total/(1<<20)/elasped);
		waitpid(pid, NULL, 0);
	}

	return 0;
}