3 /* messaging - high level communication (send/receive messages) */
4 /* module's public interface exported to end user. */
6 /* Copyright (c) 2003, 2004 Martin Quinson. All rights reserved. */
8 /* This program is free software; you can redistribute it and/or modify it
9 * under the terms of the license (GNU LGPL) which comes with this package. */
11 #ifndef GRAS_MESSAGES_H
12 #define GRAS_MESSAGES_H
15 #include "gras/transport.h"
16 #include "gras/datadesc.h"
20 /** @addtogroup GRAS_msg
21 * @brief Defining messages and callbacks, and exchanging messages
23 * There is two way to receive messages in GRAS. The first one is to
24 * register a given function as callback to a given type of messages (see
25 * \ref gras_cb_register and associated section). But you can also
26 * explicitely wait for a given message with the \ref gras_msg_wait
29 * Usually, both ways are not intended to be mixed of a given type of
30 * messages. But if you do so, it shouldn't trigger any issue. If the
31 * message arrives when gras_msg_wait is blocked, then it will be routed to
32 * it. If it arrives when before or after \ref gras_msg_wait, it will be
33 * passed to the callback.
35 * For an example of use, please refer to \ref GRAS_ex_ping.
38 /** @defgroup GRAS_msg_decl Message declaration and retrival
41 * GRAS messages can only accept one type of payload. See \ref GRAS_dd for
42 * more information on how to describe data in GRAS.
44 * If you absolutely want use a message able to convey several datatypes,
45 * you can always say that it conveys a generic reference (see
46 * \ref gras_datadesc_ref_generic).
48 * In order to ease the upgrade of GRAS applications, it is possible to \e
49 * version the messages, ie to add a version number to the message (by
50 * default, the version is set to 0). Any messages of the wrong version will
51 * be ignored by the applications not providing any specific callback for
54 * This mechanism (stolen from the dynamic loader one) should ensure you to
55 * change the semantic of a given message while still understanding the old
59 /** \brief Opaque type */
60 typedef struct s_gras_msgtype *gras_msgtype_t;
62 void gras_msgtype_declare (const char *name,
63 gras_datadesc_type_t payload);
64 void gras_msgtype_declare_v(const char *name,
66 gras_datadesc_type_t payload);
68 gras_msgtype_t gras_msgtype_by_name (const char *name);
69 gras_msgtype_t gras_msgtype_by_namev(const char *name, short int version);
70 gras_msgtype_t gras_msgtype_by_id(int id);
73 /** @defgroup GRAS_msg_rpcdecl RPC declaration
76 * Remote Procedure Call (RPC) are a classical mecanism to request a service
77 * from a remote host. Using this set of functions, you let GRAS doing most of
78 * the work of sending the request, wait for an answer, make sure it is the
79 * right answer from the right host and so on. Any exception raised on the
80 * server is also passed over the network to the client.
84 void gras_msgtype_declare_rpc(const char *name,
85 gras_datadesc_type_t payload_request,
86 gras_datadesc_type_t payload_answer);
88 void gras_msgtype_declare_rpc_v(const char *name,
90 gras_datadesc_type_t payload_request,
91 gras_datadesc_type_t payload_answer);
95 /** @defgroup GRAS_msg_cb Callback declaration and use
99 * This is how to register a given function so that it gets called when a
100 * given type of message arrives.
102 * You can register several callbacks to the same kind of messages, and
103 * they will get stacked. The lastly added callback gets the message first.
104 * If it consumes the message, it should return a true value when done. If
105 * not, it should return 0, and the message will be passed to the second
106 * callback of the stack, if any.
111 /** \brief Context of callbacks (opaque structure) */
112 typedef struct s_gras_msg_cb_ctx *gras_msg_cb_ctx_t;
114 gras_socket_t gras_msg_cb_ctx_from(gras_msg_cb_ctx_t ctx);
116 /** \brief Type of message callback functions.
118 * \param expeditor: a socket to contact who sent this message
119 * \param payload: the message itself
121 * \return true if the message was consumed by the callback,
122 * false if the message was refused by the callback (and should be
123 * passed to the next callback of the stack for this message)
125 * Once a such a function is registered to handle messages of a given
126 * type with \ref gras_cb_register(), it will be called each time such
127 * a message arrives (unless a gras_msg_wait() intercepts it on arrival).
129 * If the callback accepts the message, it should free it after use.
131 typedef int (*gras_msg_cb_t)(gras_msg_cb_ctx_t ctx,
134 void gras_cb_register (gras_msgtype_t msgtype, gras_msg_cb_t cb);
135 void gras_cb_unregister(gras_msgtype_t msgtype, gras_msg_cb_t cb);
139 /** @defgroup GRAS_msg_rpc RPC specific functions
145 void gras_msg_rpccall(gras_socket_t server,
147 gras_msgtype_t msgtype,
148 void *request, void *answer);
151 void gras_msg_rpcreturn(double timeOut, gras_msg_cb_ctx_t ctx,void *answer);
156 /** @defgroup GRAS_msg_exchange Message exchange
163 void gras_msg_send(gras_socket_t sock,
164 gras_msgtype_t msgtype,
166 void gras_msg_wait(double timeout,
167 gras_msgtype_t msgt_want,
168 gras_socket_t *expeditor,
170 void gras_msg_handle(double timeOut);
173 /** @defgroup GRAS_msg_exchangeadv Message exchange (advanced interface)
179 /** @brief Message kind (internal enum) */
181 e_gras_msg_kind_unknown = 0,
183 e_gras_msg_kind_oneway=1, /**< good old regular messages */
185 e_gras_msg_kind_rpccall=2, /**< RPC request */
186 /* HACK: e_gras_msg_kind_rpccall also designate RPC message *type* in
187 msgtype_t, not only in msg_t*/
188 e_gras_msg_kind_rpcanswer=3, /**< RPC successful answer */
189 e_gras_msg_kind_rpcerror=4, /**< RPC failure on server (payload=exception); should not leak to user-space */
192 call cancel, and others
194 forwarding request and other application level routing stuff
198 e_gras_msg_kind_count=5 /* sentinel, dont mess with */
202 /** @brief Message instance (internal struct) */
205 e_gras_msg_kind_t kind;
207 unsigned long int ID;
210 } s_gras_msg_t, *gras_msg_t;
212 typedef int (*gras_msg_filter_t)(gras_msg_t msg,void *ctx);
214 void gras_msg_wait_ext(double timeout,
215 gras_msgtype_t msgt_want,
216 gras_socket_t expe_want,
217 gras_msg_filter_t filter,
226 #endif /* GRAS_MSG_H */