/*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/

/*

 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>

 * Copyright 2007-2012 Niels Provos and Nick Mathewson

 *

 * 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.

 */

#include "event2/event-config.h"

#include <sys/types.h>

#ifdef _EVENT_HAVE_SYS_TIME_H

#include <sys/time.h>

#endif

#ifdef _EVENT_HAVE_SYS_SELECT_H

#include <sys/select.h>

#endif

#include <sys/queue.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>

#include "event-internal.h"

#include "evsignal-internal.h"

#include "event2/thread.h"

#include "evthread-internal.h"

#include "log-internal.h"

#include "evmap-internal.h"

#ifndef _EVENT_HAVE_FD_MASK

/* This type is mandatory, but Android doesn't define it. */

typedef unsigned long fd_mask;

#endif

#ifndef NFDBITS

#define NFDBITS (sizeof(fd_mask)*8)

#endif

/* Divide positive x by y, rounding up. */

#define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))

/* How many bytes to allocate for N fds? */

#define SELECT_ALLOC_SIZE(n) \

	(DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))

struct selectop {

	int event_fds;		/* Highest fd in fd set */

	int event_fdsz;

	int resize_out_sets;

	fd_set *event_readset_in;

	fd_set *event_writeset_in;

	fd_set *event_readset_out;

	fd_set *event_writeset_out;

};

static void *select_init(struct event_base *);

static int select_add(struct event_base *, int, short old, short events, void*);

static int select_del(struct event_base *, int, short old, short events, void*);

static int select_dispatch(struct event_base *, struct timeval *);

static void select_dealloc(struct event_base *);

const struct eventop selectops = {

	"select",

	select_init,

	select_add,

	select_del,

	select_dispatch,

	select_dealloc,

	0, /* doesn't need reinit. */

	EV_FEATURE_FDS,

	0,

};

static int select_resize(struct selectop *sop, int fdsz);

static void select_free_selectop(struct selectop *sop);

static void *

select_init(struct event_base *base)

{

	struct selectop *sop;

	if (!(sop = mm_calloc(1, sizeof(struct selectop))))

		return (NULL);

	if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {

		select_free_selectop(sop);

		return (NULL);

	}

	evsig_init(base);

	return (sop);

}

#ifdef CHECK_INVARIANTS

static void

check_selectop(struct selectop *sop)

{

	/* nothing to be done here */

}

#else

#define check_selectop(sop) do { (void) sop; } while (0)

#endif

static int

select_dispatch(struct event_base *base, struct timeval *tv)

{

	int res=0, i, j, nfds;

	struct selectop *sop = base->evbase;

	check_selectop(sop);

	if (sop->resize_out_sets) {

		fd_set *readset_out=NULL, *writeset_out=NULL;

		size_t sz = sop->event_fdsz;

		if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))

			return (-1);

		sop->event_readset_out = readset_out;

		if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {

			/* We don't free readset_out here, since it was

			 * already successfully reallocated. The next time

			 * we call select_dispatch, the realloc will be a

			 * no-op. */

			return (-1);

		}

		sop->event_writeset_out = writeset_out;

		sop->resize_out_sets = 0;

	}

	memcpy(sop->event_readset_out, sop->event_readset_in,

	       sop->event_fdsz);

	memcpy(sop->event_writeset_out, sop->event_writeset_in,

	       sop->event_fdsz);

	nfds = sop->event_fds+1;

	EVBASE_RELEASE_LOCK(base, th_base_lock);

	res = select(nfds, sop->event_readset_out,

	    sop->event_writeset_out, NULL, tv);

	EVBASE_ACQUIRE_LOCK(base, th_base_lock);

	check_selectop(sop);

	if (res == -1) {

		if (errno != EINTR) {

			event_warn("select");

			return (-1);

		}

		return (0);

	}

	event_debug(("%s: select reports %d", __func__, res));

	check_selectop(sop);

	i = random() % nfds;

	for (j = 0; j < nfds; ++j) {

		if (++i >= nfds)

			i = 0;

		res = 0;

		if (FD_ISSET(i, sop->event_readset_out))

			res |= EV_READ;

		if (FD_ISSET(i, sop->event_writeset_out))

			res |= EV_WRITE;

		if (res == 0)

			continue;

		evmap_io_active(base, i, res);

	}

	check_selectop(sop);

	return (0);

}

static int

select_resize(struct selectop *sop, int fdsz)

{

	fd_set *readset_in = NULL;

	fd_set *writeset_in = NULL;

	if (sop->event_readset_in)

		check_selectop(sop);

	if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)

		goto error;

	sop->event_readset_in = readset_in;

	if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {

		/* Note that this will leave event_readset_in expanded.

		 * That's okay; we wouldn't want to free it, since that would

		 * change the semantics of select_resize from "expand the

		 * readset_in and writeset_in, or return -1" to "expand the

		 * *set_in members, or trash them and return -1."

		 */

		goto error;

	}

	sop->event_writeset_in = writeset_in;

	sop->resize_out_sets = 1;

	memset((char *)sop->event_readset_in + sop->event_fdsz, 0,

	    fdsz - sop->event_fdsz);

	memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,

	    fdsz - sop->event_fdsz);

	sop->event_fdsz = fdsz;

	check_selectop(sop);

	return (0);

 error:

	event_warn("malloc");

	return (-1);

}

static int

select_add(struct event_base *base, int fd, short old, short events, void *p)

{

	struct selectop *sop = base->evbase;

	(void) p;

	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);

	check_selectop(sop);

	/*

	 * Keep track of the highest fd, so that we can calculate the size

	 * of the fd_sets for select(2)

	 */

	if (sop->event_fds < fd) {

		int fdsz = sop->event_fdsz;

		if (fdsz < (int)sizeof(fd_mask))

			fdsz = (int)sizeof(fd_mask);

		/* In theory we should worry about overflow here.  In

		 * reality, though, the highest fd on a unixy system will

		 * not overflow here. XXXX */

		while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))

			fdsz *= 2;

		if (fdsz != sop->event_fdsz) {

			if (select_resize(sop, fdsz)) {

				check_selectop(sop);

				return (-1);

			}

		}

		sop->event_fds = fd;

	}

	if (events & EV_READ)

		FD_SET(fd, sop->event_readset_in);

	if (events & EV_WRITE)

		FD_SET(fd, sop->event_writeset_in);

	check_selectop(sop);

	return (0);

}

/*

 * Nothing to be done here.

 */

static int

select_del(struct event_base *base, int fd, short old, short events, void *p)

{

	struct selectop *sop = base->evbase;

	(void)p;

	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);

	check_selectop(sop);

	if (sop->event_fds < fd) {

		check_selectop(sop);

		return (0);

	}

	if (events & EV_READ)

		FD_CLR(fd, sop->event_readset_in);

	if (events & EV_WRITE)

		FD_CLR(fd, sop->event_writeset_in);

	check_selectop(sop);

	return (0);

}

static void

select_free_selectop(struct selectop *sop)

{

	if (sop->event_readset_in)

		mm_free(sop->event_readset_in);

	if (sop->event_writeset_in)

		mm_free(sop->event_writeset_in);

	if (sop->event_readset_out)

		mm_free(sop->event_readset_out);

	if (sop->event_writeset_out)

		mm_free(sop->event_writeset_out);

	memset(sop, 0, sizeof(struct selectop));

	mm_free(sop);

}

static void

select_dealloc(struct event_base *base)

{

	evsig_dealloc(base);

	select_free_selectop(base->evbase);

}