/*
 * netio.c -- network I/O support.
 *
 * Copyright (c) 2001-2011, NLnet Labs. All rights reserved.
 *
 * See LICENSE for the license.
 *
 */
#include <config.h>

#include <assert.h>
#include <errno.h>
#include <sys/time.h>
#include <string.h>
#include <stdlib.h>

#include "netio.h"
#include "util.h"


#ifndef HAVE_PSELECT
int pselect(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
	    const struct timespec *timeout, const sigset_t *sigmask);
#else
#include <sys/select.h>
#endif


struct netio_handler_list
{
	netio_handler_list_type *next;
	netio_handler_type      *handler;
};

netio_type *
netio_create(region_type *region)
{
	netio_type *result;
	
	assert(region);

	result = (netio_type *) region_alloc(region, sizeof(netio_type));
	result->region = region;
	result->handlers = NULL;
	result->deallocated = NULL;
	result->dispatch_next = NULL;
	return result;
}

void
netio_add_handler(netio_type *netio, netio_handler_type *handler)
{
	netio_handler_list_type *elt;
	
	assert(netio);
	assert(handler);

	if (netio->deallocated) {
		/*
		 * If we have deallocated handler list elements, reuse
		 * the first one.
		 */
		elt = netio->deallocated;
		netio->deallocated = elt->next;
	} else {
		/*
		 * Allocate a new one.
		 */
		elt = (netio_handler_list_type *) region_alloc(
			netio->region, sizeof(netio_handler_list_type));
	}

	elt->next = netio->handlers;
	elt->handler = handler;
	netio->handlers = elt;
}

void
netio_remove_handler(netio_type *netio, netio_handler_type *handler)
{
	netio_handler_list_type **elt_ptr;
	
	assert(netio);
	assert(handler);

	for (elt_ptr = &netio->handlers; *elt_ptr; elt_ptr = &(*elt_ptr)->next) {
		if ((*elt_ptr)->handler == handler) {
			netio_handler_list_type *next = (*elt_ptr)->next;
			if ((*elt_ptr) == netio->dispatch_next)
				netio->dispatch_next = next;
			(*elt_ptr)->handler = NULL;
			(*elt_ptr)->next = netio->deallocated;
			netio->deallocated = *elt_ptr;
			*elt_ptr = next;
			break;
		}
	}
}

const struct timespec *
netio_current_time(netio_type *netio)
{
	assert(netio);

	if (!netio->have_current_time) {
		struct timeval current_timeval;
		if (gettimeofday(&current_timeval, NULL) == -1) {
			log_msg(LOG_CRIT, "gettimeofday: %s, aborting.", strerror(errno));
			abort();
		}
		timeval_to_timespec(&netio->cached_current_time, &current_timeval);
		netio->have_current_time = 1;
	}

	return &netio->cached_current_time;
}

int
netio_dispatch(netio_type *netio, const struct timespec *timeout, const sigset_t *sigmask)
{
	fd_set readfds, writefds, exceptfds;
	int max_fd;
	int have_timeout = 0;
	struct timespec minimum_timeout;
	netio_handler_type *timeout_handler = NULL;
	netio_handler_list_type *elt;
	int rc;
	int result = 0;
	
	assert(netio);

	/*
	 * Clear the cached current time.
	 */
	netio->have_current_time = 0;
	
	/*
	 * Initialize the minimum timeout with the timeout parameter.
	 */
	if (timeout) {
		have_timeout = 1;
		memcpy(&minimum_timeout, timeout, sizeof(struct timespec));
	}

	/*
	 * Initialize the fd_sets and timeout based on the handler
	 * information.
	 */
	max_fd = -1;
	FD_ZERO(&readfds);
	FD_ZERO(&writefds);
	FD_ZERO(&exceptfds);

	for (elt = netio->handlers; elt; elt = elt->next) {
		netio_handler_type *handler = elt->handler;
		if (handler->fd >= 0 && handler->fd < (int)FD_SETSIZE) {
			if (handler->fd > max_fd) {
				max_fd = handler->fd;
			}
			if (handler->event_types & NETIO_EVENT_READ) {
				FD_SET(handler->fd, &readfds);
			}
			if (handler->event_types & NETIO_EVENT_WRITE) {
				FD_SET(handler->fd, &writefds);
			}
			if (handler->event_types & NETIO_EVENT_EXCEPT) {
				FD_SET(handler->fd, &exceptfds);
			}
		}
		if (handler->timeout && (handler->event_types & NETIO_EVENT_TIMEOUT)) {
			struct timespec relative;

			relative.tv_sec = handler->timeout->tv_sec;
			relative.tv_nsec = handler->timeout->tv_nsec;
			timespec_subtract(&relative, netio_current_time(netio));

			if (!have_timeout ||
			    timespec_compare(&relative, &minimum_timeout) < 0)
			{
				have_timeout = 1;
				minimum_timeout.tv_sec = relative.tv_sec;
				minimum_timeout.tv_nsec = relative.tv_nsec;
				timeout_handler = handler;
			}
		}
	}

	if (have_timeout && minimum_timeout.tv_sec < 0) {
		/*
		 * On negative timeout for a handler, immediatly
		 * dispatch the timeout event without checking for
		 * other events.
		 */
		if (timeout_handler && (timeout_handler->event_types & NETIO_EVENT_TIMEOUT)) {
			timeout_handler->event_handler(netio, timeout_handler, NETIO_EVENT_TIMEOUT);
		}
		return result;
	}

	/* Check for events.  */
	rc = pselect(max_fd + 1, &readfds, &writefds, &exceptfds,
		     have_timeout ? &minimum_timeout : NULL,
		     sigmask);
	if (rc == -1) {
		if(errno == EINVAL || errno == EACCES || errno == EBADF) {
			log_msg(LOG_ERR, "fatal error pselect: %s.", 
				strerror(errno));
			exit(1);
		}
		return -1;
	}

	/*
	 * Clear the cached current_time (pselect(2) may block for
	 * some time so the cached value is likely to be old).
	 */
	netio->have_current_time = 0;
	
	if (rc == 0) {
		/*
		 * No events before the minimum timeout expired.
		 * Dispatch to handler if interested.
		 */
		if (timeout_handler && (timeout_handler->event_types & NETIO_EVENT_TIMEOUT)) {
			timeout_handler->event_handler(netio, timeout_handler, NETIO_EVENT_TIMEOUT);
		}
	} else {
		/*
		 * Dispatch all the events to interested handlers
		 * based on the fd_sets.  Note that a handler might
		 * deinstall itself, so store the next handler before
		 * calling the current handler!
		 */
		assert(netio->dispatch_next == NULL);
		for (elt = netio->handlers; elt && rc; ) {
			netio_handler_type *handler = elt->handler;
			netio->dispatch_next = elt->next;
			if (handler->fd >= 0 && handler->fd < (int)FD_SETSIZE) {
				netio_event_types_type event_types
					= NETIO_EVENT_NONE;
				if (FD_ISSET(handler->fd, &readfds)) {
					event_types |= NETIO_EVENT_READ;
					FD_CLR(handler->fd, &readfds);
					rc--;
				}
				if (FD_ISSET(handler->fd, &writefds)) {
					event_types |= NETIO_EVENT_WRITE;
					FD_CLR(handler->fd, &writefds);
					rc--;
				}
				if (FD_ISSET(handler->fd, &exceptfds)) {
					event_types |= NETIO_EVENT_EXCEPT;
					FD_CLR(handler->fd, &exceptfds);
					rc--;
				}

				if (event_types & handler->event_types) {
					handler->event_handler(netio, handler, event_types & handler->event_types);
					++result;
				}
			}
			elt = netio->dispatch_next;
		}
		netio->dispatch_next = NULL;
	}

	return result;
}