/*      $NetBSD: select.c,v 1.3 2011/11/02 16:49:12 yamt Exp $  */

/*-
 * Copyright (c)2008 YAMAMOTO Takashi,
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define FD_SETSIZE      65536
#include <sys/select.h>
#include <sys/atomic.h>
#include <sys/time.h>

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define NPIPE   128
#define NTHREAD 64
#define NBALLS  5
#define VERBOSE 0

#if !defined(RANDOM_MAX)
#define RANDOM_MAX      ((1UL << 31) - 1)
#endif

int fds[NPIPE][2];

volatile unsigned count;

pthread_barrier_t barrier;

static void
dowrite(void)
{
        char buf[1];
        int fd;
        int i;

        i = random() % NPIPE;
        fd = fds[i][1];
#if VERBOSE
        printf("[%p] write %d\n", (void *)pthread_self(), fd);
#endif
        if (write(fd, buf, sizeof(buf)) == -1) {
                perror("write");
                abort();
        }
}

static void *
f(void *dummy)
{

        pthread_barrier_wait(&barrier);

        for (;;) {
                struct timeval to;
                fd_set oset;
                fd_set set;
                int maxfd = -1;
                int nfd = 0;
                int ret;
                int fd;
                int i;

                FD_ZERO(&set);
                do {
                        for (i = 0; i < NPIPE; i++) {
                                fd = fds[i][0];
                                if (fd > FD_SETSIZE) {
                                        fprintf(stderr,
                                            "fd(%d) > FD_SETSIZE(%d)\n",
                                            fd, FD_SETSIZE);
                                        abort();
                                }
                                if (random() & 1) {
                                        assert(!FD_ISSET(fd, &set));
                                        FD_SET(fd, &set);
                                        nfd++;
                                        if (fd > maxfd) {
                                                maxfd = fd;
                                        }
                                }
                        }
                } while (nfd == 0);
                memcpy(&oset, &set, sizeof(oset));
                memset(&to, 0, sizeof(to));
                to.tv_sec = random() % 10;
                to.tv_usec = random() % 1000000;
#if VERBOSE
                printf("[%p] select start to=%lu\n", (void *)pthread_self(),
                    (unsigned long)to.tv_sec);
#endif
                ret = select(maxfd + 1, &set, NULL, NULL, &to);
#if VERBOSE
                printf("[%p] select done ret=%d\n",
                    (void *)pthread_self(), ret);
#endif
                if (ret == -1) {
                        perror("select");
                        abort();
                }
                if (ret > nfd) {
                        fprintf(stderr, "[%p] unexpected return value %d\n",
                            (void *)pthread_self(), ret);
                        abort();
                }
                if (ret > NBALLS) {
                        fprintf(stderr, "[%p] unexpected return value %d"
                            " > NBALLS\n",
                            (void *)pthread_self(), ret);
                        abort();
                }
                nfd = 0;
                for (fd = 0; fd <= maxfd; fd++) {
                        if (FD_ISSET(fd, &set)) {
                                char buf[1];

#if VERBOSE
                                printf("[%p] read %d\n",
                                    (void *)pthread_self(), fd);
#endif
                                if (!FD_ISSET(fd, &oset)) {
                                        fprintf(stderr, "[%p] unexpected\n",
                                            (void *)pthread_self());
                                        abort();
                                }
                                if (read(fd, buf, sizeof(buf)) == -1) {
                                        if (errno != EAGAIN) {
                                                perror("read");
                                                abort();
                                        }
                                } else {
                                        dowrite();
                                        atomic_inc_uint(&count);
                                }
                                nfd++;
                        }
                }
                if (ret != nfd) {
                        fprintf(stderr, "[%p] ret(%d) != nfd(%d)\n",
                            (void *)pthread_self(), ret, nfd);
                        abort();
                }
        }
}

int
main(int argc, char *argv[])
{
        pthread_t pt[NTHREAD];
        int i;
        unsigned int secs;
        struct timeval start_tv;
        struct timeval end_tv;
        uint64_t usecs;
        unsigned int result;

        secs = atoi(argv[1]);

        for (i = 0; i < NPIPE; i++) {
                if (pipe(fds[i])) {
                        perror("pipe");
                        abort();
                }
                if (fcntl(fds[i][0], F_SETFL, O_NONBLOCK) == -1) {
                        perror("fcntl");
                        abort();
                }
        }
        pthread_barrier_init(&barrier, NULL, NTHREAD + 1);
        for (i = 0; i < NTHREAD; i++) {
                int error = pthread_create(&pt[i], NULL, f, NULL);
                if (error) {
                        errno = error;
                        perror("pthread_create");
                        abort();
                }
        }
        pthread_barrier_wait(&barrier);
        gettimeofday(&start_tv, NULL);
        assert(count == 0);
        for (i = 0; i < NBALLS; i++) {
                dowrite();
        }
        sleep(secs);
        gettimeofday(&end_tv, NULL);
        result = count;
        usecs = (end_tv.tv_sec - start_tv.tv_sec) * 1000000
            + end_tv.tv_usec - start_tv.tv_usec;
        printf("%u / %f = %f\n", result, (double)usecs / 1000000,
            (double)result / usecs * 1000000);
        exit(EXIT_SUCCESS);
}