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Random notes on coding conventions, some explanations about why things

aren't done differently, etc, etc,

* Boost 1.35

Until boost 1.35 or later is common in distributions, you'll need to

build boost from source yourself.  See README.building-boost.

* C++ and Python

GNU Radio is now a hybrid system.  Some parts of the system are built

in C++ and some of it in Python.  In general, prefer Python to C++.

Signal processing primitives are still built in C++ for performance.

* C++ namespaces

In the cleanup process, I considered putting everything in the

gnuradio namespace and dropping the Gr|gr prefix.  In fact, I think

it's probably the right idea, but when I tested it out, I ran into

problems with SWIG's handling of namespaces.  Bottom line, SWIG

(1.3.21) got confused and generated bad code when I started playing

around with namespaces in a not particularly convoluted way.  I saw

problems using the boost::shared_ptr template in combination with

classes defined in the gnuradio namespace.  It wasn't pretty...

* Naming conventions

Death to CamelCaseNames!  We've returned to a kinder, gentler era.

We're now using the "STL style" naming convention with a couple of

modifications since we're not using namespaces.

With the exception of macros and other constant values, all

identifiers shall be lower case with words_separated_like_this.

Macros and constant values (e.g., enumerated values,

static const int FOO = 23) shall be in UPPER_CASE.

** Global names

All globally visible names (types, functions, variables, consts, etc)

shall begin with a "package prefix", followed by an '_'.  The bulk of

the code in GNU Radio logically belongs to the "gr" package, hence

names look like gr_open_file (...).

Large coherent bodies of code may use other package prefixes, but

let's try to keep them to a well thought out list.  See the list

below.

*** Package prefixes

These are the current package prefixes:

    gr_		Almost everything

    gri_	Implementation primitives.  Sometimes we

		have both a gr_<foo> and a gri_<foo>.  In that case,

		gr_<foo> would be derived from gr_block and gri_<foo>

		would be the low level guts of the function.

    atsc_	Code related to the Advanced Television

	       	Standards Committee HDTV implementation

    qa_		Quality Assurance.  Test code.

** Class data members (instance variables)

All class data members shall begin with d_<foo>.

The big win is when you're staring at a block of code it's obvious

which of the things being assigned to persist outside of the block.

This also keeps you from having to be creative with parameter names

for methods and constructors.  You just use the same name as the

instance variable, without the d_.

class gr_wonderfulness {

  std::string	d_name;

  double	d_wonderfulness_factor;

public:

  gr_wonderfulness (std::string name, double wonderfulness_factor)

    : d_name (name), d_wonderfulness_factor (wonderfulness_factor)

  {

    ...

  }

  ...

};

** Class static data members (class variables)

All class static data members shall begin with s_<foo>.

** File names

Each significant class shall be contained in it's own file.  The

declaration of class gr_foo shall be in gr_foo.h, the definition in

gr_foo.cc.

* Storage management

Strongly consider using the boost smart pointer templates, scoped_ptr

and shared_ptr.  scoped_ptr should be used for locals that contain

pointers to objects that we need to delete when we exit the current

scope.  shared_ptr implements transparent reference counting and is a

major win.  You never have to worry about calling delete.  The right

thing happens.

See http://www.boost.org/libs/smart_ptr/smart_ptr.htm

* Unit tests

Build unit tests for everything non-trivial and run them after every

change.  Check out Extreme Programming:

http://c2.com/cgi/wiki?ExtremeProgrammingRoadmap

Unit tests should also be written for all examples.  This should kill

off the bit rot we've been plagued with.

** C++ unit tests

For C++ we're using the cppunit framework.  cppunit has its bad

smells, but it's mostly workable.  http://cppunit.sf.net

Currently each directory <dirname> contains files qa_<dirname>.{h,cc}

that bring together all the qa_<foo> test suites in the directory.

We ought to be able to automate this without too much trouble.

The directory gnuradio-core/src/tests contains programs that run

the tests.  test_all runs all of the registered C++ unit tests.

As far as I can tell, the cppunit TestFactoryRegistry maybe able to be

tricked into doing what we want.  As is, I don't think it's enough by

itself, since there's nothing dragging the qa* files out of the

library and into the program.   I haven't tested out this idea.

** Python unit tests

We use the standard unittest package for unit testing of Python code.

* Standard command line options

When writing programs that are executable from the command line,

please follow these guidelines for command line argument names (short

and long) and types of the arguments.  We list them below using the

Python optparse syntax.  In general, the default value should be coded

into the help string using the "... [default=%default]" syntax.

** Mandatory options by gr_block

*** Audio source

Any program using an audio source shall include:

  add_option("-I", "--audio-input", type="string", default="",

             help="pcm input device name.  E.g., hw:0,0 or /dev/dsp")

The default must be "".  This allows an audio module-dependent default

to be specified in the user preferences file.

*** Audio sink

  add_option("-O", "--audio-output", type="string", default="",

             help="pcm output device name.  E.g., hw:0,0 or /dev/dsp")

The default must be "".  This allows an audio module-dependent default

to be specified in the user preferences file.

** Standard options names by parameter

Whenever you want an integer, use the "intx" type.  This allows the

user to input decimal, hex or octal numbers.  E.g., 10, 012, 0xa.

Whenever you want a float, use the "eng_float" type.  This allows the

user to input numbers with SI suffixes.  E.g, 10000, 10k, 10M, 10m, 92.1M

If your program allows the user to specify values for any of the

following parameters, please use these options to specify them:

To specify a frequency (typically an RF center frequency) use:

  add_option("-f", "--freq", type="eng_float", default=<your-default-here>,

             help="set frequency to FREQ [default=%default]")

To specify a decimation factor use:

  add_option("-d", "--decim", type="intx", default=<your-default-here>,

             help="set decimation rate to DECIM [default=%default]")

To specify an interpolation factor use:

  add_option("-i", "--interp", type="intx", default=<your-default-here>,

             help="set interpolation rate to INTERP [default=%default]")

To specify a gain setting use:

  add_option("-g", "--gain", type="eng_float", default=<your-default-here>,

	     help="set gain in dB [default=%default]")

If your application specifies both a tx and an rx gain, use:

  add_option("", "--rx-gain", type="eng_float", default=<your-default-here>,

	     help="set receive gain in dB [default=%default]")

  add_option("", "--tx-gain", type="eng_float", default=<your-default-here>,

	     help="set transmit gain in dB [default=%default]")

To specify the number of channels of something use:

  add_option("-n", "--nchannels", type="intx", default=1,

             help="specify number of channels [default=%default]")

To specify an output filename use:

  add_option("-o", "--output-filename", type="string", default=<your-default-here>,

             help="specify output-filename [default=%default]")

To specify a rate use:

  add_option("-r", "--bit-rate", type="eng_float", default=<your-default-here>,

             help="specify bit-rate [default=%default]")

     or

  add_option("-r", "--sample-rate", type="eng_float", default=<your-default-here>,

             help="specify sample-rate [default=%default]")

If your application has a verbose option, use:

  add_option('-v', '--verbose', action="store_true", default=False,

	     help="verbose output")

If your application allows the user to specify the "fast USB" options, use:

  add_option("", "--fusb-block-size", type="intx", default=0,

             help="specify fast usb block size [default=%default]")

  add_option("", "--fusb-nblocks", type="intx", default=0,

             help="specify number of fast usb blocks [default=%default]")