.** vim: ts=4 noet sw=4:
.if false
==================================================================================
	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.
==================================================================================
.fi


.if false
	Mnemonic:	config-deploy.xfm
	Abstract:	Source to generate a configuration deployment guide.
	Date:		6 November 2019
	Author:		E. Scott Daniels
.fi

.im setup.im

&h1(RMR Developer Guide)

The RIC Message Router (RMR) is a library which applications use to send and receive
messages where the message routing, endpoint selection, is based on the message type 
rather than on traditional DNS names or IP addresses. 
This document contains information that potential developers might need to know 
in order to contribute to the 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 Nanosmg, and shortly after was ported to NNG
(Nanomsg Next Generation).  
Because RMR presents the same API to the user application regardless of the underlying
transport library, the resulting output when compiling RMR is 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 or NNG), 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.

&end_dlist

&space
&h3(Internal Function Exposure)
The decision to limit as much as practical the exposure of truely 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) will directly include 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}_,) while allowing 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 are insisted on by the maintainers of RMR, 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 packages.