text: /*	$OpenBSD: poll.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
  
  /*
   * Copyright 2000-2003 Niels Provos <provos@citi.umich.edu>
   * 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.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
   */
  #ifdef HAVE_CONFIG_H
  #include "config.h"
  #endif
  
  #include <sys/types.h>
  #ifdef HAVE_SYS_TIME_H
  #include <sys/time.h>
  #else
  #include <sys/_libevent_time.h>
  #endif
  #include <sys/queue.h>
  #include <poll.h>
  #include <signal.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <errno.h>
  #ifdef CHECK_INVARIANTS
  #include <assert.h>
  #endif
  
  #include "event.h"
  #include "event-internal.h"
  #include "evsignal.h"
  #include "log.h"
  
  struct pollop {
  	int event_count;		/* Highest number alloc */
  	int nfds;                       /* Size of event_* */
  	int fd_count;                   /* Size of idxplus1_by_fd */
  	struct pollfd *event_set;
  	struct event **event_r_back;
  	struct event **event_w_back;
  	int *idxplus1_by_fd; /* Index into event_set by fd; we add 1 so
  			      * that 0 (which is easy to memset) can mean
  			      * "no entry." */
  };
  
  static void *poll_init	(struct event_base *);
  static int poll_add		(void *, struct event *);
  static int poll_del		(void *, struct event *);
  static int poll_dispatch	(struct event_base *, void *, struct timeval *);
  static void poll_dealloc	(struct event_base *, void *);
  
  const struct eventop pollops = {
  	"poll",
  	poll_init,
  	poll_add,
  	poll_del,
  	poll_dispatch,
  	poll_dealloc,
      0
  };
  
  static void *
  poll_init(struct event_base *base)
  {
  	struct pollop *pollop;
  
  	/* Disable poll when this environment variable is set */
  	if (evutil_getenv("EVENT_NOPOLL"))
  		return (NULL);
  
  	if (!(pollop = calloc(1, sizeof(struct pollop))))
  		return (NULL);
  
  	evsignal_init(base);
  
  	return (pollop);
  }
  
  #ifdef CHECK_INVARIANTS
  static void
  poll_check_ok(struct pollop *pop)
  {
  	int i, idx;
  	struct event *ev;
  
  	for (i = 0; i < pop->fd_count; ++i) {
  		idx = pop->idxplus1_by_fd[i]-1;
  		if (idx < 0)
  			continue;
  		assert(pop->event_set[idx].fd == i);
  		if (pop->event_set[idx].events & POLLIN) {
  			ev = pop->event_r_back[idx];
  			assert(ev);
  			assert(ev->ev_events & EV_READ);
  			assert(ev->ev_fd == i);
  		}
  		if (pop->event_set[idx].events & POLLOUT) {
  			ev = pop->event_w_back[idx];
  			assert(ev);
  			assert(ev->ev_events & EV_WRITE);
  			assert(ev->ev_fd == i);
  		}
  	}
  	for (i = 0; i < pop->nfds; ++i) {
  		struct pollfd *pfd = &pop->event_set[i];
  		assert(pop->idxplus1_by_fd[pfd->fd] == i+1);
  	}
  }
  #else
  #define poll_check_ok(pop)
  #endif
  
  static int
  poll_dispatch(struct event_base *base, void *arg, struct timeval *tv)
  {
  	int res, i, j, msec = -1, nfds;
  	struct pollop *pop = arg;
  
  	poll_check_ok(pop);
  
  	if (tv != NULL)
  		msec = tv->tv_sec * 1000 + (tv->tv_usec + 999) / 1000;
  
  	nfds = pop->nfds;
  	res = poll(pop->event_set, nfds, msec);
  
  	if (res == -1) {
  		if (errno != EINTR) {
                          event_warn("poll");
  			return (-1);
  		}
  
  		evsignal_process(base);
  		return (0);
  	} else if (base->sig.evsignal_caught) {
  		evsignal_process(base);
  	}
  
  	event_debug(("%s: poll reports %d", __func__, res));
  
  	if (res == 0 || nfds == 0)
  		return (0);
  
  	i = random() % nfds;
  	for (j = 0; j < nfds; j++) {
  		struct event *r_ev = NULL, *w_ev = NULL;
  		int what;
  		if (++i == nfds)
  			i = 0;
  		what = pop->event_set[i].revents;
  
  		if (!what)
  			continue;
  
  		res = 0;
  
  		/* If the file gets closed notify */
  		if (what & (POLLHUP|POLLERR))
  			what |= POLLIN|POLLOUT;
  		if (what & POLLIN) {
  			res |= EV_READ;
  			r_ev = pop->event_r_back[i];
  		}
  		if (what & POLLOUT) {
  			res |= EV_WRITE;
  			w_ev = pop->event_w_back[i];
  		}
  		if (res == 0)
  			continue;
  
  		if (r_ev && (res & r_ev->ev_events)) {
  			event_active(r_ev, res & r_ev->ev_events, 1);
  		}
  		if (w_ev && w_ev != r_ev && (res & w_ev->ev_events)) {
  			event_active(w_ev, res & w_ev->ev_events, 1);
  		}
  	}
  
  	return (0);
  }
  
  static int
  poll_add(void *arg, struct event *ev)
  {
  	struct pollop *pop = arg;
  	struct pollfd *pfd = NULL;
  	int i;
  
  	if (ev->ev_events & EV_SIGNAL)
  		return (evsignal_add(ev));
  	if (!(ev->ev_events & (EV_READ|EV_WRITE)))
  		return (0);
  
  	poll_check_ok(pop);
  	if (pop->nfds + 1 >= pop->event_count) {
  		struct pollfd *tmp_event_set;
  		struct event **tmp_event_r_back;
  		struct event **tmp_event_w_back;
  		int tmp_event_count;
  
  		if (pop->event_count < 32)
  			tmp_event_count = 32;
  		else
  			tmp_event_count = pop->event_count * 2;
  
  		/* We need more file descriptors */
  		tmp_event_set = realloc(pop->event_set,
  				 tmp_event_count * sizeof(struct pollfd));
  		if (tmp_event_set == NULL) {
  			event_warn("realloc");
  			return (-1);
  		}
  		pop->event_set = tmp_event_set;
  
  		tmp_event_r_back = realloc(pop->event_r_back,
  			    tmp_event_count * sizeof(struct event *));
  		if (tmp_event_r_back == NULL) {
  			/* event_set overallocated; that's okay. */
  			event_warn("realloc");
  			return (-1);
  		}
  		pop->event_r_back = tmp_event_r_back;
  
  		tmp_event_w_back = realloc(pop->event_w_back,
  			    tmp_event_count * sizeof(struct event *));
  		if (tmp_event_w_back == NULL) {
  			/* event_set and event_r_back overallocated; that's
  			 * okay. */
  			event_warn("realloc");
  			return (-1);
  		}
  		pop->event_w_back = tmp_event_w_back;
  
  		pop->event_count = tmp_event_count;
  	}
  	if (ev->ev_fd >= pop->fd_count) {
  		int *tmp_idxplus1_by_fd;
  		int new_count;
  		if (pop->fd_count < 32)
  			new_count = 32;
  		else
  			new_count = pop->fd_count * 2;
  		while (new_count <= ev->ev_fd)
  			new_count *= 2;
  		tmp_idxplus1_by_fd =
  			realloc(pop->idxplus1_by_fd, new_count * sizeof(int));
  		if (tmp_idxplus1_by_fd == NULL) {
  			event_warn("realloc");
  			return (-1);
  		}
  		pop->idxplus1_by_fd = tmp_idxplus1_by_fd;
  		memset(pop->idxplus1_by_fd + pop->fd_count,
  		       0, sizeof(int)*(new_count - pop->fd_count));
  		pop->fd_count = new_count;
  	}
  
  	i = pop->idxplus1_by_fd[ev->ev_fd] - 1;
  	if (i >= 0) {
  		pfd = &pop->event_set[i];
  	} else {
  		i = pop->nfds++;
  		pfd = &pop->event_set[i];
  		pfd->events = 0;
  		pfd->fd = ev->ev_fd;
  		pop->event_w_back[i] = pop->event_r_back[i] = NULL;
  		pop->idxplus1_by_fd[ev->ev_fd] = i + 1;
  	}
  
  	pfd->revents = 0;
  	if (ev->ev_events & EV_WRITE) {
  		pfd->events |= POLLOUT;
  		pop->event_w_back[i] = ev;
  	}
  	if (ev->ev_events & EV_READ) {
  		pfd->events |= POLLIN;
  		pop->event_r_back[i] = ev;
  	}
  	poll_check_ok(pop);
  
  	return (0);
  }
  
  /*
   * Nothing to be done here.
   */
  
  static int
  poll_del(void *arg, struct event *ev)
  {
  	struct pollop *pop = arg;
  	struct pollfd *pfd = NULL;
  	int i;
  
  	if (ev->ev_events & EV_SIGNAL)
  		return (evsignal_del(ev));
  
  	if (!(ev->ev_events & (EV_READ|EV_WRITE)))
  		return (0);
  
  	poll_check_ok(pop);
  	i = pop->idxplus1_by_fd[ev->ev_fd] - 1;
  	if (i < 0)
  		return (-1);
  
  	/* Do we still want to read or write? */
  	pfd = &pop->event_set[i];
  	if (ev->ev_events & EV_READ) {
  		pfd->events &= ~POLLIN;
  		pop->event_r_back[i] = NULL;
  	}
  	if (ev->ev_events & EV_WRITE) {
  		pfd->events &= ~POLLOUT;
  		pop->event_w_back[i] = NULL;
  	}
  	poll_check_ok(pop);
  	if (pfd->events)
  		/* Another event cares about that fd. */
  		return (0);
  
  	/* Okay, so we aren't interested in that fd anymore. */
  	pop->idxplus1_by_fd[ev->ev_fd] = 0;
  
  	--pop->nfds;
  	if (i != pop->nfds) {
  		/* 
  		 * Shift the last pollfd down into the now-unoccupied
  		 * position.
  		 */
  		memcpy(&pop->event_set[i], &pop->event_set[pop->nfds],
  		       sizeof(struct pollfd));
  		pop->event_r_back[i] = pop->event_r_back[pop->nfds];
  		pop->event_w_back[i] = pop->event_w_back[pop->nfds];
  		pop->idxplus1_by_fd[pop->event_set[i].fd] = i + 1;
  	}
  
  	poll_check_ok(pop);
  	return (0);
  }
  
  static void
  poll_dealloc(struct event_base *base, void *arg)
  {
  	struct pollop *pop = arg;
  
  	evsignal_dealloc(base);
  	if (pop->event_set)
  		free(pop->event_set);
  	if (pop->event_r_back)
  		free(pop->event_r_back);
  	if (pop->event_w_back)
  		free(pop->event_w_back);
  	if (pop->idxplus1_by_fd)
  		free(pop->idxplus1_by_fd);
  
  	memset(pop, 0, sizeof(struct pollop));
  	free(pop);
  }
  