README.hacking

The layout of this tree is as follows. The top-level directory contains
the autoconf/automake build definition files:

bootstrap
config.guess
config.sub
configure.ac
Makefile.am
Makefile.common
Makefile.swig
Makefile.swig.gen.t
version.sh

Of these files, only configure.ac, Makefile.am, and Makefile.common  would
likely need changing in order to customize this into a new out-of-tree
project.

Subdirectory Layout
-------------------

config  - autoconf configuration macros
lib     - GNU Radio blocks C++ API, shared lib and headers and QA code
swig    - Generates Python API from C++ blocks
python  - Pure Python modules (hierarchical blocks, other classes)
grc     - GNU Radio Companion block wrappers
apps    - GRC applications, scripts, or other executables installed to bin

The 'config' directory contains autoconf configuration files which help the
configuration script discover various things about the software development
environment during the execution of the 'configure' script.  These files
would likely not need any changing to customize this tree.

The 'lib' directory contains those files needed to generate GNU Radio
signal processing blocks.  These take the form of a shared library that one
dynamically links against, and header files that one would include in
their C++ GNU Radio application.  This directory also contains the framework
for adding QA tests that are executed during 'make check' using the cppunit
unit testing framework.  The generated shared library is installed into
$prefix/lib and the header files are installed into $prefix/include/gnuradio.

Adding new blocks starts here, by adding new .cc and new .h files for each
new block, and modifying Makefile.am to add them to the build and link.  If
desired, one can add unit tests to the QA framework that get executed during
'make check'.

The 'swig' directory contains the SWIG machinery to create a Python module
that exports the C++ API into a Python namespace.  Each GNU Radio block gets a
.i file (using SWIG syntax).  The master howto.i file must also have a line
to include the block header file and a line to import the block .i file. The
resulting _howto_swig.so and _howto_swig.py files are installed into the
system Python lib directory under gnuradio/howto and become part of the
gnuradio.howto Python namespace.  The Makefile.am must be customized to
recognize new files created here.

The 'python' directory contains pure Python modules that get installed into
the system Python lib directory under gnuradio/howto and the __init__.py
module needed to turn the directory into the gnuradio.howto namespace.
This is the appropriate place to put hierarchical blocks and utility classes.
Be sure to edit the __init__.py to add your module/symbol imports as
necessary, and to modify the Makefile.am accordingly.

This directory also contains Python-based QA code, which is executed during
'make check'.

The 'grc' directory contains the XML-based wrappers that describe your blocks
to the GNU Radio Companion graphical flowgraph editor.  These get installed
into the $prefix/share/gnuradio/grc/blocks directory and require modification
of the Makefile.am to recognize new files put here.  Note: GRC only scans the
system directory for wrapper files, so you must do a 'make install' before
GRC will see your new files or modifications to existing ones.

The 'apps' directory contains those Python and C++ programs which are to be
installed into the system $prefix/bin directory. (FIXME: there is not
currently an example of building a C++ binary in this directory.)