doc/src/rtd/developer-guide.xfm

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==================================================================================
	Copyright (c) 2019 Nokia
	Copyright (c) 2018-2019 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.
==================================================================================
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	Mnemonic:	config-deploy.xfm
	Abstract:	Source to generate a configuration deployment guide.
	Date:		6 November 2019
	Author:		E. Scott Daniels
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.im setup.im

&h1(RMR Developer Guide)

The RIC Message Router (RMR) is a library for peer-to-peer
communication.  Applications use the library to send and receive
messages where the message routing and endpoint selection is based on
the message type rather than DNS host name-IP port combinations.
&space
This document contains information that developers need to know to
contribute to the RMR project.

&h2(Language)
RMR is written in C, and thus a contributing developer to the core
library should have an excellent working knowledge of C.  There
currently is one set of cross-languages bindings supporting Python,
and a developer wishing to contribute to the bindings source should be
familiar with Python (version 3.7+) and with the Python &ital(ctypes)
library.

&h2(Code Structure)
RMR is designed to provide an insulation layer between user
applications and the actual transport mechanism.  Initially RMR was
built on top of the third-party library Nanosmg, shortly after was
ported to the third-party library NNG (Nanomsg Next Generation), and
then was ported to an internally developed socket library called SI95.
RMR presents the same API to the user application regardless of the
underlying transport library, but the resulting output when compiling
RMR is always a transport-specific library.  As an example,
&cw(librmr_nng.a) is the library generated for use with the NNG
transport.  &space

As such the library source is organised into multiple components:

&beg_dlist(.75i : ^&bold_font )

&di(common) Source in the common directory is agnostic to the
	underlying transport mechanism (Nanomsg, NNG, SI95, ..), and
	thus can be used when generating either library.

&di(nano) Source which is tightly coupled with the underlying Nanomsg library.
	(Nanomsg has been deprecated, but the RMR source remains as an example.)

&di(nng) Source which is tightly coupled with the underlying NNG library.
	(NNG has been deprecated, but the RMR source remains as an example.)

&di(si) Source which is tightly coupled with the underlying SI95 library.

&end_dlist

&space
&h3(Internal Function Exposure)
The decision to limit as much as practical the exposure of truly
internal RMR functions was made, and as a result most of the RMR
functions carry a &cw(static) label.  In order to modularise the code
as much as possible, this means that the primary module
(e.g. rmr_nng.c) directly includes other RMR modules, rather than
depending on referencing the internal functions during linking.  While
this is an infrequently used approach, it does mean that there are
very few functions visible for the user application to reference, all
of them having the prefix &cw(rmr&{esc}_). This allows internal
functions to have shorter names while still being meaningful.

&h2(Coding Style)
There is a list of coding style guidelines in the top level directory,
and as such they are not expanded upon here.  The general practice is
to follow the style when editing an existing module, respect the
author's choice where style alternatives are not frowned upon.  When
creating new modules, select a style that fits the guidelines and is
easy for you to work with.  There are a few things that the RMR
maintainers insist on, but for the most part style is up to the
creator of a module.

&h2(Building)
RMR is constructed using CMake.  While CMake's project description can
be more cumbersome than most typical Makefiles, the tool provides
convenience especially when it comes to creating DEB/RPM packages.