.if false ================================================================================== Copyright (c) 2019-2020 Nokia Copyright (c) 2018-2020 AT&T Intellectual Property. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. ================================================================================== .fi .if false Mnemonic rmr_init_man.xfm Abstract The manual page for the rmr_init function. Author E. Scott Daniels Date 28 January 2019 .fi .gv e LIB lib .im &{lib}/man/setup.im &line_len(6i) &h1(RMR Library Functions) &h2(NAME) rmr_init &h2(SYNOPSIS) &indent &ex_start #include void* rmr_init( char* proto_port, int norm_msg_size, int flags ); &ex_end &uindent &h2(DESCRIPTION) The &cw(rmr_init) function prepares the environment for sending and receiving messages. It does so by establishing a worker thread (pthread) which subscribes to a route table generator which provides the necessary routing information for the RMR library to send messages. &space &ital(Port) is used to listen for connection requests from other RMR based applications. The &ital(norm_msg_size) parameter is used to allocate receive buffers and should be set to what the user application expects to be a size which will hold the vast majority of expected messages. When computing the size, the application should consider the usual payload size &bold(and) the maximum trace data size that will be used. This value is also used as the default message size when allocating message buffers (when a zero size is given to rmr_alloc_msg(); see the rmr_alloc_msg() manual page). Messages arriving which are longer than the given normal size will cause RMR to allocate a new buffer which is large enough for the arriving message. &space Starting with version 3.8.0 RMR no longer places a maximum buffer size for received messages. The underlying system memory manager might impose such a limit and the attempt to allocate a buffer larger than that limit will likely result in an application abort. Other than the potential performance impact from extra memory allocation and release, there is no penality to the user programme for specifyning a normal buffer size which is usually smaller than received buffers. Similarly, the only penality to the application for over specifying the normal buffer size might be a larger memory footprint. &space &ital(Flags) allows for selection of some RMr options at the time of initialisation. These are set by ORing &cw(RMRFL) constants from the RMr header file. Currently the following flags are supported: &half_space &beg_dlist(1i : &bold_font ) &ditem(RMRFL_NONE) No flags are set. &half_space &ditem(RMRFL_NOTHREAD) The route table collector thread is not to be started. This should only be used by the route table generator application if it is based on RMr. &half_space &ditem(RMRFL_MTCALL) Enable multi-threaded call support. &half_space &ditem(RMRFL_NOLOCK) Some underlying transport providers (e.g. SI95) enable locking to be turned off if the user application is single threaded, or otherwise can guarantee that RMR functions will not be invoked concurrently from different threads. Turning off locking can help make message receipt more efficient. If this flag is set when the underlying transport does not support disabling locks, it will be ignored. &end_dlist &h3(Multi-threaded Calling) The support for an application to issue a &ital(blocking call) by the &cw(rmr_call()) function was limited such that only user applications which were operating in a single thread could safely use the function. Further, timeouts were message count based and not time unit based. Multi-threaded call support adds the ability for a user application with multiple threads to invoke a blocking call function with the guarantee that the correct response message is delivered to the thread. The additional support is implemented with the &ital(rmr_mt_call()) and &ital(rmr_mt_rcv()) function calls. &space Multi-threaded call support requires the user application to specifically enable it when RMr is initialised. This is necessary because a second, dedicated, receiver thread must be started, and requires all messages to be examined and queued by this thread. The additional overhead is minimal, queuing information is all in the RMr message header, but as an additional process is necessary the user application must "opt in" to this approach. &space &h2(ENVIRONMENT) As a part of the initialisation process &cw(rmr_init) reads environment variables to configure itself. The following variables are used if found. &half_space .** the list of environment vars supported .im &{lib}/man/env_var_list.im &h2(RETURN VALUE) The &cw(rmr_init) function returns a void pointer (a contex if you will) that is passed as the first parameter to nearly all other RMR functions. If &cw(rmr_init) is unable to properly initialise the environment, NULL is returned and errno is set to an appropriate value. &h2(ERRORS) The following error values are specifically set by this RMR function. In some cases the error message of a system call is propagated up, and thus this list might be incomplete. &beg_dlist(.75i : ^&bold_font ) &di(ENOMEM) Unable to allocate memory. &end_dlist &h2(EXAMPLE) &ex_start void* uh; rmr_mbuf* buf = NULL; uh = rmr_init( "43086", 4096, 0 ); buf = rmr_rcv_msg( uh, buf ); &ex_end &h2(SEE ALSO ) .ju off rmr_alloc_msg(3), rmr_call(3), rmr_free_msg(3), rmr_get_rcvfd(3), rmr_mt_call(3), rmr_mt_rcv(3), rmr_payload_size(3), rmr_send_msg(3), rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), rmr_mk_ring(3), rmr_ring_free(3) .ju on