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

#define FIFO_NAME "/tmp/fifo1"
#define BLKSIZ 65536
#define NBLK (100*(1<<20)/BLKSIZ)


int main(int argc, char *argv[])
{
	pid_t pid;
	int nonblock = 0;
	int skip_select = 0;

	if (argc >= 2 && (atoi(argv[1]) & 1)) nonblock = 1;
	if (argc >= 2 && (atoi(argv[1]) & 2)) skip_select = 1;

	mkfifo("/tmp/fifo1", 0644);

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

	return 0;
}