src/lib/dispatch/msgtypes.h

   1 /* Copyright (c) 2001, Matej Pfajfar.
   2  * Copyright (c) 2001-2004, Roger Dingledine.
   3  * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   4  * Copyright (c) 2007-2021, The Tor Project, Inc. */
   5 /* See LICENSE for licensing information */
   6
   7 /**
   8  * \file msgtypes.h
   9  * \brief Types used for messages in the dispatcher code.
  10  **/
  11
  12 #ifndef TOR_DISPATCH_MSGTYPES_H
  13 #define TOR_DISPATCH_MSGTYPES_H
  14
  15 #include <stdint.h>
  16
  17 #include "ext/tor_queue.h"
  18
  19 /**
  20  * These types are aliases for subsystems, channels, and message IDs.
  21  **/
  22 typedef uint16_t subsys_id_t;
  23 typedef uint16_t channel_id_t;
  24 typedef uint16_t message_id_t;
  25
  26 /**
  27  * This identifies a C type that can be sent along with a message.
  28  **/
  29 typedef uint16_t msg_type_id_t;
  30
  31 /**
  32  * An ID value returned for *_type_t when none exists.
  33  */
  34 #define ERROR_ID 65535
  35
  36 /**
  37  * Auxiliary (untyped) data sent along with a message.
  38  *
  39  * We define this as a union of a pointer and a u64, so that the integer
  40  * types will have the same range across platforms.
  41  **/
  42 typedef union {
  43   void *ptr;
  44   uint64_t u64;
  45 } msg_aux_data_t;
  46
  47 /**
  48  * Structure of a received message.
  49  **/
  50 typedef struct msg_t {
  51   TOR_SIMPLEQ_ENTRY(msg_t) next;
  52   subsys_id_t sender;
  53   channel_id_t channel;
  54   message_id_t msg;
  55   /** We could omit this field, since it is implicit in the message type, but
  56    * IMO let's leave it in for safety. */
  57   msg_type_id_t type;
  58   /** Untyped auxiliary data. You shouldn't have to mess with this
  59    * directly. */
  60   msg_aux_data_t aux_data__;
  61 } msg_t;
  62
  63 /**
  64  * A function that a subscriber uses to receive a message.
  65  **/
  66 typedef void (*recv_fn_t)(const msg_t *m);
  67
  68 /**
  69  * Table of functions to use for a given C type.  Any omitted (NULL) functions
  70  * will be treated as no-ops.
  71  **/
  72 typedef struct dispatch_typefns_t {
  73   /** Release storage held for the auxiliary data of this type. */
  74   void (*free_fn)(msg_aux_data_t);
  75   /** Format and return a newly allocated string describing the contents
  76    * of this data element. */
  77   char *(*fmt_fn)(msg_aux_data_t);
  78 } dispatch_typefns_t;
  79
  80 #endif /* !defined(TOR_DISPATCH_MSGTYPES_H) */