pubsub.h

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/* Copyright (c) 2016-2017, The Tor Project, Inc. */
/* See LICENSE for licensing information */

#ifndef TOR_PUBSUB_H
#define TOR_PUBSUB_H

#include "torint.h"

#define SUBSCRIBE_ATSTART (1u<<0)

#define DECLARE_PUBSUB_STRUCT_TYPES(name)                               \
  /* You define this type. */                                           \
  typedef struct name ## _event_data_t name ## _event_data_t;           \
  /* You define this type. */                                           \
  typedef struct name ## _subscriber_data_t name ## _subscriber_data_t;

#define DECLARE_PUBSUB_TOPIC(name)                                      \
  /* This type is opaque. */                                            \
  typedef struct name ## _subscriber_t name ## _subscriber_t;           \
  /* You declare functions matching this type. */                       \
  typedef int (*name ## _subscriber_fn_t)(                              \
                                    name ## _event_data_t *data,        \
                                    name ## _subscriber_data_t *extra); \
  /* Call this function to subscribe to a topic. */                     \
  const name ## _subscriber_t *name ## _subscribe(                      \
                         name##_subscriber_fn_t subscriber,             \
                         name##_subscriber_data_t *extra_data,          \
                         unsigned flags,                                \
                         unsigned priority);                            \
  /* Call this function to unsubscribe from a topic. */                 \
  int name ## _unsubscribe(const name##_subscriber_t *s);

#define DECLARE_NOTIFY_PUBSUB_TOPIC(linkage, name)                          \
  /* Call this function to notify all subscribers. Flags not yet used. */   \
  linkage int name ## _notify(name ## _event_data_t *data, unsigned flags); \
  /* Call this function to release storage held by the topic. */            \
  linkage void name ## _clear(void);

typedef int (*pubsub_subscriber_fn_t)(void *, void *);

typedef struct pubsub_subscriber_t {
  pubsub_subscriber_fn_t fn;
  void *subscriber_data;
  unsigned priority;
  unsigned subscriber_flags;
} pubsub_subscriber_t;

typedef struct pubsub_topic_t {
  struct smartlist_t *subscribers;
  uint64_t n_events_fired;
  unsigned locked;
} pubsub_topic_t;

const pubsub_subscriber_t *pubsub_subscribe_(pubsub_topic_t *topic,
                                             pubsub_subscriber_fn_t fn,
                                             void *subscriber_data,
                                             unsigned subscribe_flags,
                                             unsigned priority);
int pubsub_unsubscribe_(pubsub_topic_t *topic, const pubsub_subscriber_t *sub);
void pubsub_clear_(pubsub_topic_t *topic);
typedef int (*pubsub_notify_fn_t)(pubsub_subscriber_t *subscriber,
                                  void *notify_data);
int pubsub_notify_(pubsub_topic_t *topic, pubsub_notify_fn_t notify_fn,
                   void *notify_data, unsigned notify_flags);

#define IMPLEMENT_PUBSUB_TOPIC(notify_linkage, name)                    \
  static pubsub_topic_t name ## _topic_ = { NULL, 0, 0 };               \
  const name ## _subscriber_t *                                         \
  name ## _subscribe(name##_subscriber_fn_t subscriber,                 \
                     name##_subscriber_data_t *extra_data,              \
                     unsigned flags,                                    \
                     unsigned priority)                                 \
  {                                                                     \
    const pubsub_subscriber_t *s;                                       \
    s = pubsub_subscribe_(&name##_topic_,                               \
                          (pubsub_subscriber_fn_t)subscriber,           \
                          extra_data,                                   \
                          flags,                                        \
                          priority);                                    \
    return (const name##_subscriber_t *)s;                              \
  }                                                                     \
  int                                                                   \
  name ## _unsubscribe(const name##_subscriber_t *subscriber)           \
  {                                                                     \
    return pubsub_unsubscribe_(&name##_topic_,                          \
                               (const pubsub_subscriber_t *)subscriber); \
  }                                                                     \
  static int                                                            \
  name##_call_the_notify_fn_(pubsub_subscriber_t *subscriber,           \
                             void *notify_data)                         \
  {                                                                     \
    name ## _subscriber_fn_t fn;                                        \
    fn = (name ## _subscriber_fn_t) subscriber->fn;                     \
    return fn(notify_data, subscriber->subscriber_data);                \
  }                                                                     \
  notify_linkage int                                                    \
  name ## _notify(name ## _event_data_t *event_data, unsigned flags)    \
  {                                                                     \
    return pubsub_notify_(&name##_topic_,                               \
                          name##_call_the_notify_fn_,                   \
                          event_data,                                   \
                          flags);                                       \
  }                                                                     \
  notify_linkage void                                                   \
  name ## _clear(void)                                                  \
  {                                                                     \
    pubsub_clear_(&name##_topic_);                                      \
  }

#endif /* !defined(TOR_PUBSUB_H) */