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/* Copyright (c) 2001, Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* @file pubsub.h
* @brief Header for OO publish-subscribe functionality.
*
* This module provides a wrapper around the "dispatch" module,
* ensuring type-safety and allowing us to do static analysis on
* publication and subscriptions.
*
* With this module, we enforce:
* <ul>
* <li>that every message has (potential) publishers and subscribers;
* <li>that every message is published and subscribed from the correct
* channels, with the correct type ID, every time it is published.
* <li>that type IDs correspond to a single C type, and that the C types are
* used correctly.
* <li>that when a message is published or subscribed, it is done with
* a correct subsystem identifier
* </ul>
*
* We do this by making "publication requests" and "subscription requests"
* into objects, and doing some computation on them before we create
* a dispatch_t with them.
*
* Rather than using the dispatch module directly, a publishing module
* receives a "binding" object that it uses to send messages with the right
* settings.
*
* Most users of this module will want to use this header, and the
* pubsub_macros.h header for convenience.
*/
/*
*
* Overview: Messages are sent over channels. Before sending a message on a
* channel, or receiving a message on a channel, a subsystem needs to register
* that it publishes, or subscribes, to that message, on that channel.
*
* Messages, channels, and subsystems are represented internally as short
* integers, though they are associated with human-readable strings for
* initialization and debugging.
*
* When registering for a message, a subsystem must say whether it is an
* exclusive publisher/subscriber to that message type, or whether other
* subsystems may also publish/subscribe to it.
*
* All messages and their publishers/subscribers must be registered early in
* the initialization process.
*
* By default, it is an error for a message type to have publishers and no
* subscribers on a channel, or subscribers and no publishers on a channel.
*
* A subsystem may register for a message with a note that delivery or
* production is disabled -- for example, because the subsystem is
* disabled at compile-time. It is not an error for a message type to
* have all of its publishers or subscribers disabled.
*
* After a message is sent, it is delivered to every recipient. This
* delivery happens from the top level of the event loop; it may be
* interleaved with network events, timers, etc.
*
* Messages may have associated data. This data is typed, and is owned
* by the message. Strings, byte-arrays, and integers have built-in
* support. Other types may be added. If objects are to be sent,
* they should be identified by handle. If an object requires cleanup,
* it should be declared with an associated free function.
*
* Semantically, if two subsystems communicate only by this kind of
* message passing, neither is considered to depend on the other, though
* both are considered to have a dependency on the message and on any
* types it contains.
*
* (Or generational index?)
*/
#ifndef TOR_PUBSUB_PUBSUB_H
#define TOR_PUBSUB_PUBSUB_H
#include "lib/pubsub/pub_binding_st.h"
#include "lib/pubsub/pubsub_connect.h"
#include "lib/pubsub/pubsub_flags.h"
#include "lib/pubsub/pubsub_macros.h"
#include "lib/pubsub/pubsub_publish.h"
#endif /* !defined(TOR_PUBSUB_PUBSUB_H) */
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