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 (Communication facility)
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
32 * to it. If it arrives when before or after gras_msg_wait, it will be
33 * passed to the callback.
35 * For an example of use, please refer to \ref GRAS_ex_ping.
40 /** @name Message declaration and retrival
42 * GRAS messages can only accept one type of payload. If you absolutely want to declare a message
43 * able to convey several datatypes, you can always say that it conveys a generic reference (see
44 * \ref gras_datadesc_ref_generic).
46 * In order to ease the upgrade of GRAS applications, it is possible to \e version the messages, ie
47 * to add a version number to the message (by default, the version is set to 0). Any messages of the
48 * wrong version will be ignored by the applications not providing any specific callback for them.
50 * This mecanism (stolen from the dynamic loader one) should ensure you to change the semantic of a given
51 * message while still understanding the old one.
54 /** \brief Opaque type */
55 typedef struct s_gras_msgtype *gras_msgtype_t;
57 /** \brief declare a new message type of the given name. It only accepts the given datadesc as payload */
58 void gras_msgtype_declare (const char *name,
59 gras_datadesc_type_t payload);
60 /** \brief declare a new versionned message type of the given name and payload. */
61 void gras_msgtype_declare_v(const char *name,
63 gras_datadesc_type_t payload);
65 /** \brief retrive an existing message type from its name. */
66 gras_msgtype_t gras_msgtype_by_name (const char *name);
67 /** \brief retrive an existing message type from its name and version number. */
68 gras_msgtype_t gras_msgtype_by_namev(const char *name,
72 /** @name Callback declaration and use
74 * This is how to register a given function so that it gets called when a
75 * given type of message arrives.
77 * You can register several callbacks to the same kind of messages, and
78 * they will get stacked. The lastly added callback gets the message first.
79 * If it consumes the message, it should return a true value when done. If
80 * not, it should return 0, and the message will be passed to the second
81 * callback of the stack, if any.
86 /** \brief Type of message callback functions.
87 * \param msg: The message itself
88 * \return true if the message was consumed by the callback, false if the message was
89 * refused by the callback (and should be passed to the next callback of the stack for
92 * Once a such a function is registered to handle messages of a given type with
93 * \ref gras_cb_register(), it will be called each time such a message arrives.
95 * If the callback accepts the message, it should free it after use.
97 typedef int (*gras_cb_t)(gras_socket_t expeditor,
99 /** \brief Bind the given callback to the given message type
101 * Several callbacks can be attached to a given message type. The lastly added one will get the message first, and
102 * if it returns false, the message will be passed to the second one.
103 * And so on until one of the callbacks accepts the message.
105 void gras_cb_register (gras_msgtype_t msgtype,
107 /** \brief Unbind the given callback from the given message type */
108 void gras_cb_unregister(gras_msgtype_t msgtype,
112 /** @name Message exchange */
114 /** \brief Send the data pointed by \a payload as a message of type \a msgtype to the peer \a sock */
115 xbt_error_t gras_msg_send(gras_socket_t sock,
116 gras_msgtype_t msgtype,
118 /** \brief Waits for a message to come in over a given socket. */
119 xbt_error_t gras_msg_wait(double timeout,
120 gras_msgtype_t msgt_want,
121 gras_socket_t *expeditor,
123 xbt_error_t gras_msg_handle(double timeOut);
129 #endif /* GRAS_MSG_H */