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Diffstat (limited to 'src/common/pubsub.h')
| -rw-r--r-- | src/common/pubsub.h | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/src/common/pubsub.h b/src/common/pubsub.h new file mode 100644 index 0000000000..bbb4f02a42 --- /dev/null +++ b/src/common/pubsub.h @@ -0,0 +1,179 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file pubsub.h + * \brief Macros to implement publish/subscribe abstractions. + * + * To use these macros, call DECLARE_PUBSUB_TOPIC() with an identifier to use + * as your topic. Below, I'm going to assume you say DECLARE_PUBSUB_TOPIC(T). + * + * Doing this will declare the following types: + * typedef struct T_event_data_t T_event_data_t; // you define this struct + * typedef struct T_subscriber_data_t T_subscriber_data_t; // this one too. + * typedef struct T_subscriber_t T_subscriber_t; // opaque + * typedef int (*T_subscriber_fn_t)(T_event_data_t*, T_subscriber_data_t*); + * + * and it will declare the following functions: + * const T_subscriber_t *T_subscribe(T_subscriber_fn_t, + * T_subscriber_data_t *, + * unsigned flags, + * unsigned priority); + * int T_unsubscribe(const T_subscriber_t *) + * + * Elsewhere you can say DECLARE_NOTIFY_PUBSUB_TOPIC(static, T), which + * declares: + * + * static int T_notify(T_event_data_t *, unsigned notify_flags); + * static void T_clear(void); + * + * And in some C file, you would define these functions with: + * IMPLEMENT_PUBSUB_TOPIC(static, T). + * + * The implementations will be small typesafe wrappers over generic versions + * of the above functions. + * + * To use the typesafe functions, you add any number of subscribers with + * T_subscribe(). Each has an associated function pointer, data pointer, + * and priority. Later, you can invoke T_notify() to declare that the + * event has occurred. Each of the subscribers will be invoked once. + **/ + +#ifndef TOR_PUBSUB_H +#define TOR_PUBSUB_H + +#include "torint.h" + +/** + * Flag for T_subscribe: die with an assertion failure if the event + * have ever been published before. Used when a subscriber must absolutely + * never have missed an event. + */ +#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); + +/** + * Type used to hold a generic function for a subscriber. + * + * [Yes, it is safe to cast to this, so long as we cast back to the original + * type before calling. From C99: "A pointer to a function of one type may be + * converted to a pointer to a function of another type and back again; the + * result shall compare equal to the original pointer."] +*/ +typedef int (*pubsub_subscriber_fn_t)(void *, void *); + +/** + * Helper type to implement pubsub abstraction. Don't use this directly. + * It represents a subscriber. + */ +typedef struct pubsub_subscriber_t { + /** Function to invoke when the event triggers. */ + pubsub_subscriber_fn_t fn; + /** Data associated with this subscriber. */ + void *subscriber_data; + /** Priority for this subscriber. Low priorities happen first. */ + unsigned priority; + /** Flags set on this subscriber. Not yet used.*/ + unsigned subscriber_flags; +} pubsub_subscriber_t; + +/** + * Helper type to implement pubsub abstraction. Don't use this directly. + * It represents a topic, and keeps a record of subscribers. + */ +typedef struct pubsub_topic_t { + /** List of subscribers to this topic. May be NULL. */ + struct smartlist_t *subscribers; + /** Total number of times that pubsub_notify_() has ever been called on this + * topic. */ + uint64_t n_events_fired; + /** True iff we're running 'notify' on this topic, and shouldn't allow + * any concurrent modifications or events. */ + 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 /* TOR_PUBSUB_H */ + |