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4 Copyright (c) 2018-2019 AT&T Intellectual Property.
6 Licensed under the Apache License, Version 2.0 (the "License");
7 you may not use this file except in compliance with the License.
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17 ==================================================================================
21 Mnemonic rmr_init_man.xfm
22 Abstract The manual page for the rmr_init function.
23 Author E. Scott Daniels
27 .** if formatting with tfm, the roff.im will cause roff output to be generated
28 .** if formatting with pfm, then pretty postscript will be generated
31 .im &{lib}/generic_ps.im
33 .gv e OUTPUT_RST use_rst
43 &h1(RMR Library Functions)
52 void* rmr_init( char* proto_port, int max_msg_size, int flags );
58 The &cw(rmr_init) function prepares the environment for sending and receiving messages.
59 It does so by establishing a worker thread (pthread) which subscribes to a route table
60 generator which provides the necessary routing information for the RMR library to
64 &ital(Port) is used to listen for connection requests from other RMR based applications.
65 The value of &ital(max_msg_size) will be used when allocating zero copy send buffers
66 which must be allocated, possibly, prior to the application knowing the actual size of
70 &ital(Flags) allows for selection of some RMr options at the time of initialisation.
71 These are set by ORing &cw(RMRFL_) constants from the RMr header file. Currently the
72 following flags are supported:
75 &beg_dlist(1i : &bold_font )
80 &ditem(RMRFL_NOTHREAD)
81 The route table collector thread is not to be started. This should only be used
82 by the route table generator application if it is based on RMr.
86 Enable multi-threaded call support.
89 &h3(Multi-threaded Calling)
90 The support for an application to issue a &ital(blocking call) by the &cw(rmr_call()) function
91 was limited such that only user applications which were operating in a single thread
92 could safely use the function.
93 Further, timeouts were message count based and not time unit based.
94 Multi-threaded call support adds the ability for a user application with multiple threads
95 to invoke a blocking call function with the guarentee that the correct response message
96 is delivered to the thread.
97 The additional support is implemented with the &ital( rmr_mt_call() ) and &ital( rmr_mt_rcv() )
101 Multi-threaded call support requires the user application to specifically enable it
102 when RMr is initialised.
103 This is necessary because a second, dedicated, receiver thread must be started, and
104 requires all messages to be examined and queued by this thread.
105 The additional overhead is minimal, queuing information is all in the RMr message
106 header, but as an additional process is necessary the user application must "opt in"
111 As a part of the initialisation process &cw(rmr_init) will look into the available
112 environment variables to influence it's setup.
113 The following variables will be used when found.
116 &beg_dlist(1i : &bold_font )
118 Assumes this is the filename of the seed route table file to use. In normal situations,
119 the library will wait for an update from the route table generator (expected within a few seconds
120 of initialisation) before being able to send messages.
121 However, in some situations where a bootstrap table is necessary, this is the means to
122 supply it to the library.
126 The route table generator assumes that RMr is listening on a well known port (4561) by
127 default, but this environment variable can be used to change the listening port if
129 The value of the variable is expected to be just the port.
133 The &cw(rmr_init) function returns a void pointer (a contex if you will) that is passed
134 as the first parameter to nearly all other RMR functions.
135 If &cw(rmr_init) is unable to properly initialise the environment, NULL is returned and
136 errno is set to an appropriate value.
139 The following error values are specifically set by this RMR function. In some cases the
140 error message of a system call is propagated up, and thus this list might be incomplete.
142 &beg_dlist(.75i : ^&bold_font )
143 &di(ENOMEM) Unable to allocate memory.
149 rmr_mbuf* buf = NULL;
151 uh = rmr_init( "43086", 4096, 0 );
152 buf = rmr_rcv_msg( uh, buf );