102 lines
4.5 KiB
C
102 lines
4.5 KiB
C
/* $NetBSD: changelist-internal.h,v 1.1.1.1 2013/04/11 16:43:29 christos Exp $ */
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/*
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* Copyright (c) 2009-2012 Niels Provos and Nick Mathewson
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _CHANGELIST_H_
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#define _CHANGELIST_H_
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/*
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A "changelist" is a list of all the fd status changes that should be made
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between calls to the backend's dispatch function. There are a few reasons
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that a backend would want to queue changes like this rather than processing
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them immediately.
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1) Sometimes applications will add and delete the same event more than
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once between calls to dispatch. Processing these changes immediately
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is needless, and potentially expensive (especially if we're on a system
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that makes one syscall per changed event).
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2) Sometimes we can coalesce multiple changes on the same fd into a single
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syscall if we know about them in advance. For example, epoll can do an
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add and a delete at the same time, but only if we have found out about
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both of them before we tell epoll.
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3) Sometimes adding an event that we immediately delete can cause
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unintended consequences: in kqueue, this makes pending events get
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reported spuriously.
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*/
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#include "event2/util.h"
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/** Represents a */
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struct event_change {
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/** The fd or signal whose events are to be changed */
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evutil_socket_t fd;
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/* The events that were enabled on the fd before any of these changes
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were made. May include EV_READ or EV_WRITE. */
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short old_events;
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/* The changes that we want to make in reading and writing on this fd.
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* If this is a signal, then read_change has EV_CHANGE_SIGNAL set,
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* and write_change is unused. */
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ev_uint8_t read_change;
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ev_uint8_t write_change;
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};
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/* Flags for read_change and write_change. */
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/* If set, add the event. */
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#define EV_CHANGE_ADD 0x01
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/* If set, delete the event. Exclusive with EV_CHANGE_ADD */
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#define EV_CHANGE_DEL 0x02
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/* If set, this event refers a signal, not an fd. */
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#define EV_CHANGE_SIGNAL EV_SIGNAL
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/* Set for persistent events. Currently not used. */
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#define EV_CHANGE_PERSIST EV_PERSIST
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/* Set for adding edge-triggered events. */
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#define EV_CHANGE_ET EV_ET
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/* The value of fdinfo_size that a backend should use if it is letting
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* changelist handle its add and delete functions. */
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#define EVENT_CHANGELIST_FDINFO_SIZE sizeof(int)
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/** Set up the data fields in a changelist. */
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void event_changelist_init(struct event_changelist *changelist);
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/** Remove every change in the changelist, and make corresponding changes
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* in the event maps in the base. This function is generally used right
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* after making all the changes in the changelist. */
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void event_changelist_remove_all(struct event_changelist *changelist,
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struct event_base *base);
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/** Free all memory held in a changelist. */
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void event_changelist_freemem(struct event_changelist *changelist);
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/** Implementation of eventop_add that queues the event in a changelist. */
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int event_changelist_add(struct event_base *base, evutil_socket_t fd, short old, short events,
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void *p);
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/** Implementation of eventop_del that queues the event in a changelist. */
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int event_changelist_del(struct event_base *base, evutil_socket_t fd, short old, short events,
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void *p);
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#endif
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