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<h1 class="header-title text-uppercase">Hurricane Python/C++ API Tutorial</h1>
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<!-- -*- mode: rst; explicit-buffer-name: "PythonCpp_HTML.rst<pelican>" -*- -->
<!-- -*- Mode: rst; explicit-buffer-name: "definition.rst<documentation/etc>" -*- -->
<!-- HTML/LaTeX backends mixed macros. -->
<!-- Acronyms & names. -->
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<p>Printable version of this document <a class="reference external" href="../pdfs/PythonCpp.pdf">PythonCpp.pdf</a>.</p>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#introduction" id="id7">1. Introduction</a></li>
<li><a class="reference internal" href="#basic-file-structure-and-cmake-configuration" id="id8">2. Basic File Structure and CMake configuration</a></li>
<li><a class="reference internal" href="#case-1-dbo-derived-standalone" id="id9">3. Case 1 - DBo Derived, Standalone</a></li>
<li><a class="reference internal" href="#case-2-hierarchy-of-dbo-derived-classes" id="id10">4. Case 2 - Hierarchy of DBo Derived Classes</a></li>
<li><a class="reference internal" href="#case-3-non-dbo-standalone-classe" id="id11">5. Case 3 - Non-DBo Standalone Classe</a></li>
<li><a class="reference internal" href="#encapsulating-dbu" id="id12">6. Encapsulating DbU</a></li>
<li><a class="reference internal" href="#no-c-hurricane-name-encapsulation" id="id13">7. No C++ Hurricane::Name encapsulation</a></li>
</ul>
</div>
<!-- -*- Mode: rst -*- -->
<div class="section" id="introduction">
<h2><a class="toc-backref" href="#id7">1. Introduction</a></h2>
<ul class="simple">
<li>This document is written for people already familiar with the
<a class="reference external" href="https://docs.python.org/2/c-api/index.html">Python/C API Reference Manual</a>.</li>
<li>The macros provided by the Hurricane Python/C API are written using
the standard Python C/API. That is, you may not use them and write
directly your functions with the original API or any mix between.
You only have to respect some naming convention.</li>
<li>Coriolis is build against Python 2.7.</li>
</ul>
<div class="section" id="first-a-disclaimer">
<h3>1.1 First, A Disclaimer</h3>
<p>The Hurricane Python/C++ API has been written about ten years ago, at a time
my mastering of template programming was less than complete. This is why this
interface is build with old fashioned C macro instead of C++ template.</p>
<p>It is my hope that at some point in the future I will have time to completly
rewrite it, borrowing the interface from <tt class="docutils literal"><span class="pre">boost::python</span></tt>.</p>
</div>
<div class="section" id="about-technical-choices">
<h3>1.2 About Technical Choices</h3>
<p>Some would say, why not use <em>off the shelf</em> wrappers like <tt class="docutils literal">swig</tt>
or <tt class="docutils literal"><span class="pre">boost::python</span></tt>, here are some clues.</p>
<ol class="arabic">
<li><p class="first"><strong>Partial exposure of the C++ class tree.</strong> We expose at Python level
C++ base classes, only if they provides common methods that we want
to see. Otherwise, we just show them as base classes under Python.
For instance <tt class="docutils literal">Library</tt> is derived from <tt class="docutils literal">DBo</tt>, but we won't see
it under Python.</p>
</li>
<li><p class="first"><strong>Bi-directional communication.</strong> When a Python object is deleted, the
wrapper obviously has a pointer toward the underlying C++ object and
is able to delete it. But, the reverse case can occurs, meaning that
you have a C++ object wrapped in Python and the database delete the
underlying object. The wrapped Python object <em>must</em> be informed that
it no longer refer a valid C++ one. Moreover, as we do not control
when Python objects gets deleteds (that is, when their reference count
reaches zero), we can have valid Python object with a dangling
C++ pointer. So our Python objects can be warned by the C++ objects
that they are no longer valid and any other operation than the
deletion should result in a severe non-blocking error.</p>
<p>To be precise, this apply to persistent object in the C++ database,
like <tt class="docutils literal">Cell</tt>, <tt class="docutils literal">Net</tt>, <tt class="docutils literal">Instance</tt> or <tt class="docutils literal">Component</tt>. Short lived
objects like <tt class="docutils literal">Box</tt> or <tt class="docutils literal">Point</tt> retains the classic Python behavior.</p>
<p>Another aspect is that, for all derived <tt class="docutils literal">DBo</tt> objects, one and only
one Python object is associated. For one given <tt class="docutils literal">Instance</tt> object we
will always return the <em>same</em> <tt class="docutils literal">PyInstance</tt> object, thanks to the
bi-directional link. Obviously, the <em>reference count</em> of the
<tt class="docutils literal">PyInstance</tt> is managed accordingly. This mechanism is implemented
by the <tt class="docutils literal">PyInstance_Link()</tt> function.</p>
</li>
<li><p class="first"><strong>Linking accross modules.</strong> As far as I understand, the wrappers
are for monolithic libraries. That is, you wrap the entire library
in one go. But Hurricane has a modular design, the core database
then various tools. We do not, and cannot, have one gigantic wrapper
that would encompass all the libraries in one go. We do one Python
module for one C++ library.</p>
<p>This brings another issue, at Python level this time. The Python
modules for the libraries have to share some functions. Python
provides a mechanism to pass C function pointers accross modules,
but I did found it cumbersome. Instead, all our modules are split
in two:</p>
<ul class="simple">
<li>The first part contains the classic Python module code.</li>
<li>The second part is to be put in a separate dynamic library that
will hold the shared functions. The Python module is dynamically linked
against that library like any other. And any other Python module
requiring the functions will link against the associated shared
library.</li>
</ul>
<p>Each module file will be compiled <em>twice</em>, once to build the Python
module (<tt class="docutils literal">__PYTHON_MODULE</tt> is defined) and once to build the supporting
shared library (<tt class="docutils literal">__PYTHON_MODULE__</tt> <strong>not</strong> defined). This tricky
double compilation is taken care of though the <tt class="docutils literal">add_python_module</tt>
<tt class="docutils literal">cmake</tt> macro.</p>
<p>For the core Hurricane library we will have:</p>
<ul class="simple">
<li><tt class="docutils literal">Hurricane.so</tt> the Python module (use with: <tt class="docutils literal">import Hurricane</tt>).</li>
<li><tt class="docutils literal">libisobar.so.1.0</tt> the supporting shared library.</li>
</ul>
<p>The <tt class="docutils literal">PyLibrary.cpp</tt> file will have the following structure:</p>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyLibrary.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#if defined(__PYTHON_MODULE__)</span>
<span class="c1">// +=================================================================+</span>
<span class="c1">// | &quot;PyLibrary&quot; Python Module Code Part |</span>
<span class="c1">// +=================================================================+</span>
<span class="c1">//</span>
<span class="c1">// The classic part of a Python module. Goes into Hurricane.so.</span>
<span class="cp">#else </span><span class="c1">// End of Python Module Code Part.</span>
<span class="c1">// x=================================================================x</span>
<span class="c1">// | &quot;PyLibrary&quot; Shared Library Code Part |</span>
<span class="c1">// x=================================================================x</span>
<span class="c1">//</span>
<span class="c1">// Functions here will be part of the associated shared library and</span>
<span class="c1">// made available to all other Python modules. Goes into libisobar.so.1.0</span>
<span class="cp"># endif </span><span class="c1">// Shared Library Code Part.</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
</pre></div>
<p>This way, we do not rely upon a pointer transmission through Python
modules, but directly uses linker capabilities.</p>
</li>
</ol>
</div>
<div class="section" id="botched-design">
<h3>1.3 Botched Design</h3>
<p>The mechanism to compute the signature of a call to a Python function,
the <tt class="docutils literal">__cs</tt> object, is much too complex and, in fact, not needed.
At some point I may root it out, but it is used in so many places...</p>
<p>What I should have used the <tt class="docutils literal">&quot;O!&quot;</tt> capablity of <tt class="docutils literal">PyArg_ParseTuple()</tt>,
like in the code below:</p>
<p></p>
<div class="highlight"><pre><span></span><span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyContact_create</span> <span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Contact</span><span class="o">*</span> <span class="n">contact</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="n">PyNet</span><span class="o">*</span> <span class="n">pyNet</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">PyLayer</span><span class="o">*</span> <span class="n">pyLayer</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">PyComponent</span><span class="o">*</span> <span class="n">pyComponent</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">DbU</span><span class="o">::</span><span class="n">Unit</span> <span class="n">x</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="n">DbU</span><span class="o">::</span><span class="n">Unit</span> <span class="n">y</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="n">DbU</span><span class="o">::</span><span class="n">Unit</span> <span class="n">width</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="n">DbU</span><span class="o">::</span><span class="n">Unit</span> <span class="n">height</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">PyArg_ParseTuple</span><span class="p">(</span> <span class="n">args</span><span class="p">,</span> <span class="s">&quot;O!O!ll|ll:Contact.create&quot;</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeNet</span> <span class="p">,</span> <span class="o">&amp;</span><span class="n">pyNet</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeLayer</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">pyLayer</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">x</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">y</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">width</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">height</span><span class="p">))</span> <span class="p">{</span>
<span class="n">contact</span> <span class="o">=</span> <span class="n">Contact</span><span class="o">::</span><span class="n">create</span><span class="p">(</span> <span class="n">PYNET_O</span><span class="p">(</span><span class="n">pyNet</span><span class="p">),</span> <span class="n">PYLAYER_O</span><span class="p">(</span><span class="n">pyLayer</span><span class="p">)</span>
<span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">width</span><span class="p">,</span> <span class="n">height</span> <span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="n">PyErr_Clear</span><span class="p">();</span>
<span class="k">if</span> <span class="p">(</span><span class="n">PyArg_ParseTuple</span><span class="p">(</span> <span class="n">args</span><span class="p">,</span> <span class="s">&quot;O!O!ll|ll:Contact.create&quot;</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeComponent</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">pyComponent</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeLayer</span> <span class="p">,</span> <span class="o">&amp;</span><span class="n">pyLayer</span>
<span class="p">,</span> <span class="o">&amp;</span><span class="n">x</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">y</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">width</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">height</span><span class="p">))</span> <span class="p">{</span>
<span class="n">contact</span> <span class="o">=</span> <span class="n">Contact</span><span class="o">::</span><span class="n">create</span><span class="p">(</span> <span class="n">PYCOMPONENT_O</span><span class="p">(</span><span class="n">pyComponent</span><span class="p">),</span> <span class="n">PYLAYER_O</span><span class="p">(</span><span class="n">pyLayer</span><span class="p">)</span>
<span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">width</span><span class="p">,</span> <span class="n">height</span> <span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Contact constructor.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="n">PyContact_Link</span><span class="p">(</span> <span class="n">contact</span> <span class="p">);</span>
<span class="p">}</span>
</pre></div>
<!-- -*- Mode: rst -*- -->
</div>
</div>
<div class="section" id="basic-file-structure-and-cmake-configuration">
<h2><a class="toc-backref" href="#id8">2. Basic File Structure and CMake configuration</a></h2>
<p>As a first example we will consider the <tt class="docutils literal"><span class="pre">Hurrican::Library</span></tt>
class. To export a class into Python, we must create three files:</p>
<ol class="arabic simple">
<li><tt class="docutils literal">PyLibrary.h</tt>, defines the <tt class="docutils literal">PyLibrary</tt> C-Struct and the functions
needed outside the module istself (mostly for <tt class="docutils literal">PyHurricane.cpp</tt>).</li>
<li><tt class="docutils literal">PyLibrary.cpp</tt>, contains the complete wrapping of the class and
the Python type definition (<tt class="docutils literal">PyTypeLibrary</tt>).</li>
<li><tt class="docutils literal">PyHurricane.cpp</tt>, the definition of the Python module into which
the classes are registered. The module act as a <tt class="docutils literal">namespace</tt> in
Python so it is good practice to give it the same name as it's
associated C++ namespace.</li>
</ol>
<p></p>
<p>To build a Python module in <span class="cb">cmake</span>, use the following macro:</p>
<div class="highlight"><pre><span></span> <span class="nb">set</span><span class="p">(</span> <span class="s">pyCpps</span> <span class="s">PyLibrary.cpp</span>
<span class="s">PyHurricane.cpp</span> <span class="p">)</span>
<span class="nb">set</span><span class="p">(</span> <span class="s">pyIncludes</span> <span class="s">hurricane/isobar/PyLibrary.h</span>
<span class="s">add_python_module(</span> <span class="s2">&quot;${pyCpps}&quot;</span>
<span class="s2">&quot;${pyIncludes}&quot;</span>
<span class="s2">&quot;isobar;1.0;1&quot;</span> <span class="c"># Name &amp; version of the supporting</span>
<span class="c"># shared library.</span>
<span class="s">Hurricane</span> <span class="c"># Name of the Python module will give:</span>
<span class="c"># Hurricane.so</span>
<span class="s2">&quot;${depLibs}&quot;</span> <span class="c"># List of dependency libraries.</span>
<span class="s">include/coriolis2/hurricane/isobar</span>
<span class="c"># Where to install the include files.</span>
<span class="p">)</span>
</pre></div>
<!-- -*- Mode: rst -*- -->
</div>
<div class="section" id="case-1-dbo-derived-standalone">
<h2><a class="toc-backref" href="#id9">3. Case 1 - DBo Derived, Standalone</a></h2>
<p>As example, we take <tt class="docutils literal">Library</tt>. This a <tt class="docutils literal">DBo</tt> derived class, but we
choose not to export the parent classes. From Python, it will appear
as a base class.</p>
<div class="section" id="id3">
<span id="class-associated-header-file"></span><span id="id2"></span><h3>3.1 Class Associated Header File</h3>
<p>Here is the typical content of a header file (for <tt class="docutils literal">PyLibrary</tt>):</p>
<div class="highlight"><pre><span></span><span class="cp">#ifndef PY_LIBRARY_H</span>
<span class="cp">#define PY_LIBRARY_H</span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyHurricane.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/Library.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="n">PyObject_HEAD</span>
<span class="n">Library</span><span class="o">*</span> <span class="n">_object</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyLibrary</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyTypeObject</span> <span class="n">PyTypeLibrary</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyMethodDef</span> <span class="n">PyLibrary_Methods</span><span class="p">[];</span>
<span class="k">extern</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyLibrary_Link</span> <span class="p">(</span> <span class="n">Hurricane</span><span class="o">::</span><span class="n">Library</span><span class="o">*</span> <span class="n">lib</span> <span class="p">);</span>
<span class="k">extern</span> <span class="kt">void</span> <span class="nf">PyLibrary_LinkPyType</span> <span class="p">();</span>
<span class="cp">#define IsPyLibrary(v) ( (v)-&gt;ob_type == &amp;PyTypeLibrary )</span>
<span class="cp">#define PYLIBRARY(v) ( (PyLibrary*)(v) )</span>
<span class="cp">#define PYLIBRARY_O(v) ( PYLIBRARY(v)-&gt;_object )</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
<span class="cp">#endif </span><span class="c1">// PY_LIBRARY_H</span>
</pre></div>
<p>The code is organized as follow:</p>
<ol class="arabic">
<li><p class="first">It must have, <em>as the first include</em> <tt class="docutils literal">PyHurricane.h</tt>, which provides
the complete bunch of macros needed to build the module. Then the include
of the C++ class we want to wrap (<tt class="docutils literal">Library.h</tt>).</p>
</li>
<li><p class="first">As Python is written in C, all the wrapper code has to be but inside
an <tt class="docutils literal">extern &quot;C&quot;</tt> namespace.</p>
</li>
<li><p class="first">Definition of the wrapped <span class="cb">struct</span>, <tt class="docutils literal">PyLibrary</tt>. It is standard Python here.</p>
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">For our set of macros to work, the name of the pointer to the
C++ class must always be <strong>_object</strong>, and the various functions and
macros defined here must take the name of the class (either in
lowercase, camel case or capitals).</p>
</div>
</li>
<li><p class="first">Declaration of the Python type <tt class="docutils literal">PyTypeLibrary</tt> (standard).</p>
</li>
<li><p class="first">Declaration of the Python type table of methods <tt class="docutils literal">PyLibrary_Methods</tt> (standard).</p>
</li>
</ol>
<ol class="arabic simple" id="id4" start="6">
<li>Declaration of <tt class="docutils literal">PyLibrary_Link()</tt>, helper to convert a C++ <tt class="docutils literal">Lybrary</tt> into
a <tt class="docutils literal">PyLibrary</tt> (put in the support shared library).</li>
<li>Declaration of <tt class="docutils literal">PyLibrary_LinkPyType()</tt>, this function setup the class-level
function of the new Python type (here, <tt class="docutils literal">PyTypeLibrary</tt>).</li>
<li>And, lastly, three macros to:<ul>
<li><tt class="docutils literal">IsPylibrary()</tt>, know if a Python object is a <tt class="docutils literal">PyLibrary</tt></li>
<li><tt class="docutils literal">PYLIBRARY()</tt>, force cast (C style) of a <tt class="docutils literal">PyObject</tt> into a <tt class="docutils literal">PyLibrary</tt>.</li>
<li><tt class="docutils literal">PYLIBRARY_O()</tt>, extract the C++ object (<tt class="docutils literal">Library*</tt>) from the Python
object (<tt class="docutils literal">PyLibrary</tt>).</li>
</ul>
</li>
</ol>
</div>
<div class="section" id="id5">
<span id="class-associated-file"></span><h3>3.2 Class Associated File</h3>
<div class="section" id="head-of-the-file">
<h4>3.2.1 Head of the file</h4>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyLibrary.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyDataBase.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyCell.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#define METHOD_HEAD(function) GENERIC_METHOD_HEAD(Library,lib,function)</span>
</pre></div>
<p>As for the header, all the code must be put inside a <tt class="docutils literal">extern &quot;C&quot;</tt> namespace.</p>
<p>A convenience macro <tt class="docutils literal">METHOD_HEAD()</tt> must be defined, by refining
<tt class="docutils literal">GENERIC_METHOD_HEAD()</tt>. This macro will be used in the method wrappers
below to cast the <tt class="docutils literal">_object</tt> field of the Python object into the
appropriate C++ class, this is done using a C-style cast.
The parameters of that macro are:</p>
<ol class="arabic simple">
<li>The C++ encapsulated class (<tt class="docutils literal">Library</tt>).</li>
<li>The name of the <em>variable</em> that will be used to store a pointer
to the C++ working object.</li>
<li>The name of the C++ method which is to be wrapped.</li>
</ol>
</div>
<div class="section" id="the-python-module-part">
<h4>3.2.2 The Python Module Part</h4>
<p>First, we have to build all the wrappers to the C++ methods of
the class. For common predicates, accessors, and mutators macros
are supplied.</p>
<p>Wrapping of the <tt class="docutils literal"><span class="pre">Library::getCell()</span></tt> method:</p>
<div class="highlight"><pre><span></span><span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyLibrary_getCell</span> <span class="p">(</span> <span class="n">PyLibrary</span><span class="o">*</span> <span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Cell</span><span class="o">*</span> <span class="n">cell</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="n">METHOD_HEAD</span><span class="p">(</span> <span class="s">&quot;Library.getCell()&quot;</span> <span class="p">)</span>
<span class="kt">char</span><span class="o">*</span> <span class="n">name</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">PyArg_ParseTuple</span><span class="p">(</span><span class="n">args</span><span class="p">,</span><span class="s">&quot;s:Library.getCell&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">name</span><span class="p">))</span> <span class="p">{</span>
<span class="n">cell</span> <span class="o">=</span> <span class="n">lib</span><span class="o">-&gt;</span><span class="n">getCell</span><span class="p">(</span> <span class="n">Name</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Library::getCell.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="n">PyCell_Link</span><span class="p">(</span><span class="n">cell</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
<p>Key points about this method wrapper:</p>
<ol class="arabic simple">
<li>The <tt class="docutils literal">HTRY</tt> / <tt class="docutils literal">HCATCH</tt> macros provides an insulation from the C++
exceptions. If one is emitted, it will be catched and transformed in
a Python one. This way, the Python program will be cleanly interrupted
and the usual stack trace displayed.</li>
<li>The returned value of this method is of type <tt class="docutils literal">Cell*</tt>, we have to
transform it into a Python one. This is done with <tt class="docutils literal">PyCell_Link()</tt>.
This macro is supplied by the <tt class="docutils literal">PyCell.h</tt> header and this is why
it must be included.</li>
</ol>
<p></p>
<p>Wrapping of the <tt class="docutils literal"><span class="pre">Library::create()</span></tt> method:</p>
<div class="highlight"><pre><span></span><span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyLibrary_create</span><span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">arg0</span><span class="p">;</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">arg1</span><span class="p">;</span>
<span class="n">Library</span><span class="o">*</span> <span class="n">library</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">init</span><span class="p">(</span> <span class="s">&quot;Library.create&quot;</span> <span class="p">);</span> <span class="c1">// Step (1).</span>
<span class="k">if</span> <span class="p">(</span><span class="n">not</span> <span class="n">PyArg_ParseTuple</span><span class="p">(</span> <span class="n">args</span><span class="p">,</span> <span class="s">&quot;O&amp;O&amp;:Library.create&quot;</span>
<span class="p">,</span> <span class="n">Converter</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">arg0</span>
<span class="p">,</span> <span class="n">Converter</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">arg1</span> <span class="p">))</span> <span class="p">{</span> <span class="c1">// Step (2).</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Library constructor.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">if</span> <span class="p">(</span><span class="n">__cs</span><span class="p">.</span><span class="n">getObjectIds</span><span class="p">()</span> <span class="o">==</span> <span class="s">&quot;:db:string&quot;</span><span class="p">)</span> <span class="p">{</span> <span class="c1">// Step (3.a)</span>
<span class="n">DataBase</span><span class="o">*</span> <span class="n">db</span> <span class="o">=</span> <span class="n">PYDATABASE_O</span><span class="p">(</span><span class="n">arg0</span><span class="p">);</span>
<span class="n">library</span> <span class="o">=</span> <span class="n">Library</span><span class="o">::</span><span class="n">create</span><span class="p">(</span> <span class="n">db</span><span class="p">,</span> <span class="n">Name</span><span class="p">(</span><span class="n">PyString_AsString</span><span class="p">(</span><span class="n">arg1</span><span class="p">))</span> <span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">__cs</span><span class="p">.</span><span class="n">getObjectIds</span><span class="p">()</span> <span class="o">==</span> <span class="s">&quot;:library:string&quot;</span><span class="p">)</span> <span class="p">{</span> <span class="c1">// Step (3.b)</span>
<span class="n">Library</span><span class="o">*</span> <span class="n">masterLibrary</span> <span class="o">=</span> <span class="n">PYLIBRARY_O</span><span class="p">(</span><span class="n">arg0</span><span class="p">);</span>
<span class="n">library</span> <span class="o">=</span> <span class="n">Library</span><span class="o">::</span><span class="n">create</span><span class="p">(</span> <span class="n">masterLibrary</span><span class="p">,</span> <span class="n">Name</span><span class="p">(</span><span class="n">PyString_AsString</span><span class="p">(</span><span class="n">arg1</span><span class="p">))</span> <span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Library constructor.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="n">PyLibrary_Link</span><span class="p">(</span> <span class="n">library</span> <span class="p">);</span>
<span class="p">}</span>
</pre></div>
<p>Key point about this constructor:</p>
<ol class="arabic simple">
<li>We want the Python interface to mimic as closely as possible the
C++ API. As such, Python object will be created using a static
<tt class="docutils literal">.create()</tt> method. So we do not use the usual Python allocation
mechanism.</li>
<li>As it is a <em>static</em> method, there is no first argument.</li>
<li>Python do not allow function overload like C++. To emulate that
behavior we use the <tt class="docutils literal">__cs</tt> object (which is a global variable).<ol class="arabic">
<li>Init/reset the <tt class="docutils literal">__cs</tt> object: see <em>step (1)</em>.</li>
<li>Call <tt class="docutils literal">PyArg_ParseTuple()</tt>, read every mandatory or optional
argument as a Python object (<tt class="docutils literal">&quot;O&amp;&quot;</tt>) and use <tt class="docutils literal">Converter</tt>
on each one. <tt class="docutils literal">Converter</tt> will determine the real type of
the Python object given as argument by looking at the
encapsulated C++ class. It then update the <tt class="docutils literal">__cs</tt> object.
Done in <em>step (2)</em></li>
<li>After the call to <tt class="docutils literal">PyArg_ParseTuple()</tt>, the function
<tt class="docutils literal">__cs.getObjectIds()</tt> will return the <em>signature</em> of
the various arguments. In our case, the valid signatures
will be <tt class="docutils literal">&quot;:db:string&quot;</tt> (<em>step (3.a)*a) and ``&quot;:library:string&quot;``
(*step (3.b)</em>).</li>
<li>Call the C++ method after extracting the C++ objects from
the Python arguments. Note the use of the <tt class="docutils literal">PYLIBRARY_O()</tt>
and <tt class="docutils literal">PYDATABSE_O()</tt> macros to perform the conversion.</li>
</ol>
</li>
<li>Return the result, encapsulated through a call to <tt class="docutils literal">PyLibrary_Link()</tt>.</li>
</ol>
<p></p>
<p>Wrapping of the <tt class="docutils literal"><span class="pre">Library::destroy()</span></tt> method:</p>
<div class="highlight"><pre><span></span><span class="n">DBoDestroyAttribute</span><span class="p">(</span><span class="n">PyLibrary_destroy</span><span class="p">,</span> <span class="n">PyLibrary</span><span class="p">)</span>
</pre></div>
<p>For C++ classes <strong>that are derived</strong> from <tt class="docutils literal">DBo</tt>, the destroy method
wrapper must be defined using the macro <tt class="docutils literal">DBoDestroyAttribute()</tt>.
This macro implements the bi-directional communication mechanism
using <tt class="docutils literal"><span class="pre">Hurricane::Property</span></tt>. It <strong>must not</strong> be used for
non <tt class="docutils literal">DBo</tt> derived classes.</p>
<p>Defining the method table of the PyLibrary type:</p>
<div class="highlight"><pre><span></span><span class="n">PyMethodDef</span> <span class="n">PyLibrary_Methods</span><span class="p">[]</span> <span class="o">=</span>
<span class="p">{</span> <span class="p">{</span> <span class="s">&quot;create&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyLibrary_create</span> <span class="p">,</span> <span class="n">METH_VARARGS</span><span class="o">|</span><span class="n">METH_STATIC</span>
<span class="p">,</span> <span class="s">&quot;Creates a new library.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getCell&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyLibrary_getCell</span><span class="p">,</span> <span class="n">METH_VARARGS</span>
<span class="p">,</span> <span class="s">&quot;Get the cell of name &lt;name&gt;&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;destroy&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyLibrary_destroy</span><span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Destroy associated hurricane object The python object remains.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span><span class="nb">NULL</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">}</span> <span class="cm">/* sentinel */</span>
<span class="p">};</span>
</pre></div>
<p>This is standard Python/C API. The name of the <tt class="docutils literal">PyMethodDef</tt> table must be
named from the class: <tt class="docutils literal">PyLibrary_Methods</tt>.</p>
</div>
<div class="section" id="python-type-linking">
<h4>3.2.3 Python Type Linking</h4>
<p>Defining the <tt class="docutils literal">PyTypeLibrary</tt> class methods and the type linking function.</p>
<p>Those are the functions for the Python object itself to work, not the
wrapped method from the C++ class.</p>
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">At this point we <strong>do not</strong> define the <tt class="docutils literal">PyTypeLibrary</tt> itself.
Only it's functions and a function to set them up <em>once</em> the
type will be defined.</p>
</div>
<div class="highlight"><pre><span></span><span class="n">DBoDeleteMethod</span><span class="p">(</span><span class="n">Library</span><span class="p">)</span>
<span class="n">PyTypeObjectLinkPyType</span><span class="p">(</span><span class="n">Library</span><span class="p">)</span>
</pre></div>
<p>The macro <tt class="docutils literal">DBoDeleteMethod()</tt> define the function to delete a
<tt class="docutils literal">PyLibrary</tt> <em>Python</em> object. Again, do not mistake it for the deletion
of the C++ class (implemented by <tt class="docutils literal">DBoDestroyAttribute()</tt>).
Here again, <tt class="docutils literal">DBoDeleteMethod()</tt> is specially tailored for
<tt class="docutils literal">DBo</tt> derived classes.</p>
<p id="pylibrary-linkpytype">To define <tt class="docutils literal">PyLibrary_LinkPyType()</tt>, use the <tt class="docutils literal">PyTypeObjectLinkPyType()</tt>
macro. This macro is specific for <tt class="docutils literal">DBo</tt> derived classes that are seen as
base classes under Python (i.e. we don't bother exposing the base
class under Python). <tt class="docutils literal">PyLibrary_LinkPyType()</tt> setup the class functions
in the <tt class="docutils literal">PyTypeLibrary</tt> type object, it <strong>must</strong> be called in the
Python module this class is part of (in this case: <tt class="docutils literal">PyHurricane.cpp</tt>).
This particular flavor of the macro <em>will define</em> and setup the
following class functions:</p>
<ul class="simple">
<li><tt class="docutils literal">PyTypeLibrary.tp_compare</tt> (defined by the macro).</li>
<li><tt class="docutils literal">PyTypeLibrary.tp_repr</tt> (defined by the macro).</li>
<li><tt class="docutils literal">PyTypeLibrary.tp_str</tt> (defined by the macro).</li>
<li><tt class="docutils literal">PyTypeLibrary.tp_hash</tt> (defined by the macro).</li>
<li><tt class="docutils literal">PyTypeLibrary.tp_methods</tt> sets to the previously defined <tt class="docutils literal">PyLibrary_Methods</tt> table.</li>
<li><tt class="docutils literal">PyTypeLibrary.tp_dealloc</tt> is set to a function that <em>must</em> be named <tt class="docutils literal">PyLibrary_DeAlloc</tt>,
this is what <tt class="docutils literal">DBoDeleteMethod</tt> does. It is <em>not</em> done by <tt class="docutils literal">PyTypeObjectLinkPyType</tt>.</li>
</ul>
<p>Defining the <tt class="docutils literal">PyTypeLibrary</tt> type:</p>
</div>
<div class="section" id="the-shared-library-part">
<h4>3.2.4 The Shared Library Part</h4>
<p>This part will be put in a separate supporting shared library, allowing
other Python module to link against it (and make use of its symbols).</p>
<div class="highlight"><pre><span></span><span class="n">DBoLinkCreateMethod</span><span class="p">(</span><span class="n">Library</span><span class="p">)</span>
<span class="n">PyTypeObjectDefinitions</span><span class="p">(</span><span class="n">Library</span><span class="p">)</span>
</pre></div>
<p>To define <tt class="docutils literal">PyTypeLibrary</tt>, use the <tt class="docutils literal">PyTypeObjectDefinitions()</tt> macro.
This macro is specific for classes that, as exposed by Python,
are neither <em>derived</em> classes nor <em>base</em> classes for others.
That is, they are standalone from the inheritance point of view.</p>
<p>The <tt class="docutils literal">DBoLinkCreateMethod()</tt> macro will define the <tt class="docutils literal">PyLibrary_Link()</tt>
function which is responsible for encapsulating a C++ <tt class="docutils literal">Library</tt> object
into a Python <tt class="docutils literal">PyLibrary</tt> one.</p>
</div>
</div>
<div class="section" id="python-module-c-namespace">
<h3>3.3 Python Module (C++ namespace)</h3>
<p>We use the Python module to replicate the C++ <em>namespace</em>. Thus, for the
<tt class="docutils literal">Hurricane</tt> namespace we create a Python <tt class="docutils literal">Hurricane</tt> module which is
defined in the <tt class="docutils literal">PyHurricane.cpp</tt> file, then we add into that module
dictionary all the Python types encapsulating the C++ classes of that
namespace.</p>
<div class="highlight"><pre><span></span><span class="n">DL_EXPORT</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span> <span class="n">initHurricane</span> <span class="p">()</span>
<span class="p">{</span>
<span class="n">PyLibrary_LinkPyType</span><span class="p">();</span> <span class="c1">// step 1.</span>
<span class="n">PYTYPE_READY</span><span class="p">(</span> <span class="n">Library</span> <span class="p">)</span> <span class="c1">// step 2.</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">addType</span><span class="p">(</span> <span class="s">&quot;library&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeLibrary</span><span class="p">,</span> <span class="s">&quot;&lt;Library&gt;&quot;</span><span class="p">,</span> <span class="nb">false</span> <span class="p">);</span> <span class="c1">// step 3.</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">module</span> <span class="o">=</span> <span class="n">Py_InitModule</span><span class="p">(</span> <span class="s">&quot;Hurricane&quot;</span><span class="p">,</span> <span class="n">PyHurricane_Methods</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">module</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;[ERROR]</span><span class="se">\n</span><span class="s">&quot;</span>
<span class="o">&lt;&lt;</span> <span class="s">&quot; Failed to initialize Hurricane module.&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">endl</span><span class="p">;</span>
<span class="k">return</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">Py_INCREF</span><span class="p">(</span> <span class="o">&amp;</span><span class="n">PyTypeLibrary</span> <span class="p">);</span> <span class="c1">// step 4.</span>
<span class="n">PyModule_AddObject</span><span class="p">(</span> <span class="n">module</span><span class="p">,</span> <span class="s">&quot;Library&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)</span><span class="o">&amp;</span><span class="n">PyTypeLibrary</span> <span class="p">);</span> <span class="c1">// step 4.</span>
<span class="p">}</span>
</pre></div>
<p>The <tt class="docutils literal">initHurricane()</tt> initialisation function shown above has
been scrubbed of everything not relevant to the <tt class="docutils literal">PyLibrary</tt> class.
The integration of the <tt class="docutils literal">PyLibrary</tt> class into the module needs
four steps:</p>
<ol class="arabic">
<li><p class="first">A call to <a class="reference internal" href="#pylibrary-linkpytype">PyLibrary_LinkPyType()</a> to hook the Python type functions
in the Python type object.</p>
</li>
<li><p class="first">A call to the <tt class="docutils literal">PYTYPE_READY()</tt> macro (standard Python).</p>
</li>
<li><p class="first">Registering the type into the <tt class="docutils literal">__cs</tt> object, with <tt class="docutils literal">addType()</tt>.
The arguments are self explanatory, save for the last which is a
boolean to tell if this is a <em>derived</em> class or not.</p>
</li>
<li><p class="first">Adding the type object (<tt class="docutils literal">PyTypeLibrary</tt>) into the dictionnary of
the module itself. This allow to mimic closely the C++ syntax:</p>
<div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">Hurricane</span>
<span class="n">lib</span> <span class="o">=</span> <span class="n">Hurricane</span><span class="o">.</span><span class="n">Library</span><span class="o">.</span><span class="n">create</span><span class="p">(</span> <span class="n">db</span><span class="p">,</span> <span class="s1">&#39;root&#39;</span> <span class="p">)</span>
</pre></div>
</li>
</ol>
<!-- -*- Mode: rst -*- -->
<p></p>
</div>
</div>
<div class="section" id="case-2-hierarchy-of-dbo-derived-classes">
<h2><a class="toc-backref" href="#id10">4. Case 2 - Hierarchy of DBo Derived Classes</a></h2>
<p>Now we want to export the following C++ class hierarchy into Python:</p>
<pre class="literal-block">
PyEntity &lt;-- PyComponent &lt;-+- PyContact
+- PySegment &lt;-+- PyHorizontal
+- PyVertical
</pre>
<div class="section" id="base-class-header">
<h3>4.1 Base Class Header</h3>
<p><strong>Remark:</strong> this is only a partial description of the tree for the sake of
clarity.</p>
<p>One important fact to remember is that <tt class="docutils literal">PyEntity</tt> and <tt class="docutils literal">PyComponent</tt>
being related to C++ abstract classes, no objects of those types will be
created, only <tt class="docutils literal">PyContact</tt>, <tt class="docutils literal">PyHorizontal</tt> or <tt class="docutils literal">PyVertical</tt> will.</p>
<p>The consequence is that there is no <tt class="docutils literal">PyEntity_Link()</tt> like in <cite>3.1</cite>
but instead two functions:</p>
<ol class="arabic simple">
<li><tt class="docutils literal">PyEntity_NEW()</tt> which create the relevant <tt class="docutils literal">PyEntity</tt> <em>derived</em>
object from the <tt class="docutils literal">Entity</tt> one. For example, if the <tt class="docutils literal">Entity*</tt> given
as argument is in fact a <tt class="docutils literal">Horizontal*</tt>, then the function will
return a <tt class="docutils literal">PyHorizontal*</tt>.</li>
<li><tt class="docutils literal">EntityCast()</tt> do the reverse of <tt class="docutils literal">PyEntity_NEW()</tt> that is, from
a <tt class="docutils literal">PyEntity</tt>, return the C++ <em>derived</em> object. Again, if the
<tt class="docutils literal">PyEntity*</tt> is a <tt class="docutils literal">PyHorizontal*</tt>, the function will cast it as
a <tt class="docutils literal">Horizontal*</tt> <em>then</em> return it as an <tt class="docutils literal">Entity*</tt>.</li>
</ol>
<div class="highlight"><pre><span></span><span class="c1">#ifndef ISOBAR_PY_ENTITY_H</span>
<span class="c1">#define ISOBAR_PY_ENTITY_H</span>
<span class="c1">#include &quot;hurricane/isobar/PyHurricane.h&quot;</span>
<span class="c1">#include &quot;hurricane/Entity.h&quot;</span>
<span class="n">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="n">extern</span> <span class="s2">&quot;C&quot;</span> <span class="p">{</span>
<span class="n">typedef</span> <span class="n">struct</span> <span class="p">{</span>
<span class="n">PyObject_HEAD</span>
<span class="n">Hurricane</span><span class="p">::</span><span class="n">Entity</span><span class="o">*</span> <span class="n">_object</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyEntity</span><span class="p">;</span>
<span class="n">extern</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">PyEntity_NEW</span> <span class="p">(</span> <span class="n">Hurricane</span><span class="p">::</span><span class="n">Entity</span><span class="o">*</span> <span class="n">entity</span> <span class="p">);</span>
<span class="n">extern</span> <span class="n">void</span> <span class="n">PyEntity_LinkPyType</span> <span class="p">();</span>
<span class="n">extern</span> <span class="n">PyTypeObject</span> <span class="n">PyTypeEntity</span><span class="p">;</span>
<span class="n">extern</span> <span class="n">PyMethodDef</span> <span class="n">PyEntity_Methods</span><span class="p">[];</span>
<span class="c1">#define IsPyEntity(v) ( (v)-&gt;ob_type == &amp;PyTypeEntity )</span>
<span class="c1">#define PYENTITY(v) ( (PyEntity*)(v) )</span>
<span class="c1">#define PYENTITY_O(v) ( PYENTITY(v)-&gt;_object )</span>
<span class="p">}</span> <span class="o">//</span> <span class="n">extern</span> <span class="s2">&quot;C&quot;</span><span class="o">.</span>
<span class="n">Hurricane</span><span class="p">::</span><span class="n">Entity</span><span class="o">*</span> <span class="n">EntityCast</span> <span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">derivedObject</span> <span class="p">);</span>
<span class="p">}</span> <span class="o">//</span> <span class="n">Isobar</span> <span class="n">namespace</span><span class="o">.</span>
<span class="c1">#endif // ISOBAR_PY_ENTITY_H</span>
</pre></div>
<p></p>
</div>
<div class="section" id="base-class-file">
<h3>4.2 Base Class File</h3>
<p>Changes from <cite>3.2 Class Associated File</cite> are:</p>
<ol class="arabic simple">
<li>No call to <tt class="docutils literal">DBoLinkCreateMethod()</tt> because there must be no <tt class="docutils literal">PyEntity_Link()</tt>,
but the definitions of <tt class="docutils literal">PyEntity_NEW()</tt> and <tt class="docutils literal">EntityCast</tt>.</li>
<li>For defining the <tt class="docutils literal">PyTypeEntity</tt> Python type, we call a different
macro: <tt class="docutils literal">PyTypeRootObjectDefinitions</tt>, dedicated to base classes.</li>
</ol>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyCell.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyHorizontal.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyVertical.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyContact.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#if defined(__PYTHON_MODULE__)</span>
<span class="cp">#define METHOD_HEAD(function) GENERIC_METHOD_HEAD(Entity,entity,function)</span>
<span class="n">DBoDestroyAttribute</span><span class="p">(</span><span class="n">PyEntity_destroy</span> <span class="p">,</span><span class="n">PyEntity</span><span class="p">)</span>
<span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">PyEntity_getCell</span> <span class="p">(</span> <span class="n">PyEntity</span> <span class="o">*</span><span class="n">self</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Cell</span><span class="o">*</span> <span class="n">cell</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="nf">METHOD_HEAD</span><span class="p">(</span> <span class="s">&quot;Entity.getCell()&quot; )</span>
<span class="n">cell</span> <span class="o">=</span> <span class="n">entity</span><span class="o">-&gt;</span><span class="n">getCell</span><span class="p">();</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="nf">PyCell_Link</span><span class="p">(</span> <span class="n">cell</span> <span class="p">);</span>
<span class="p">}</span>
<span class="n">PyMethodDef</span> <span class="n">PyEntity_Methods</span><span class="p">[]</span> <span class="o">=</span>
<span class="p">{</span> <span class="p">{</span> <span class="s">&quot;getCell&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyEntity_getCell</span><span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Returns the entity cell.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;destroy&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyEntity_destroy</span><span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Destroy associated hurricane object, the python object remains.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span><span class="nb">NULL</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">}</span> <span class="cm">/* sentinel */</span>
<span class="p">};</span>
<span class="n">DBoDeleteMethod</span><span class="p">(</span><span class="n">Entity</span><span class="p">)</span>
<span class="n">PyTypeObjectLinkPyType</span><span class="p">(</span><span class="n">Entity</span><span class="p">)</span>
<span class="cp">#else </span><span class="c1">// End of Python Module Code Part.</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">PyEntity_NEW</span> <span class="p">(</span> <span class="n">Entity</span><span class="o">*</span> <span class="n">entity</span> <span class="p">)</span>
<span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="n">not</span> <span class="n">entity</span><span class="p">)</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span> <span class="p">(</span> <span class="n">HurricaneError</span><span class="p">,</span> <span class="s">&quot;Invalid Entity (bad occurrence)&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">Horizontal</span><span class="o">*</span> <span class="n">horizontal</span> <span class="o">=</span> <span class="k">dynamic_cast</span><span class="o">&lt;</span><span class="n">Horizontal</span><span class="o">*&gt;</span><span class="p">(</span><span class="n">entity</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">horizontal</span><span class="p">)</span> <span class="k">return</span> <span class="n">PyHorizontal_Link</span><span class="p">(</span> <span class="n">horizontal</span> <span class="p">);</span>
<span class="n">Vertical</span><span class="o">*</span> <span class="n">vertical</span> <span class="o">=</span> <span class="k">dynamic_cast</span><span class="o">&lt;</span><span class="n">Vertical</span><span class="o">*&gt;</span><span class="p">(</span><span class="n">entity</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">vertical</span><span class="p">)</span> <span class="k">return</span> <span class="n">PyVertical_Link</span><span class="p">(</span> <span class="n">vertical</span> <span class="p">);</span>
<span class="n">Contact</span><span class="o">*</span> <span class="n">contact</span> <span class="o">=</span> <span class="k">dynamic_cast</span><span class="o">&lt;</span><span class="n">Contact</span><span class="o">*&gt;</span><span class="p">(</span><span class="n">entity</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">contact</span><span class="p">)</span> <span class="k">return</span> <span class="n">PyContact_Link</span><span class="p">(</span> <span class="n">contact</span> <span class="p">);</span>
<span class="n">Py_RETURN_NONE</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">PyTypeRootObjectDefinitions</span><span class="p">(</span><span class="n">Entity</span><span class="p">)</span>
<span class="cp">#endif </span><span class="c1">// Shared Library Code Part (1).</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="cp">#if !defined(__PYTHON_MODULE__)</span>
<span class="n">Hurricane</span><span class="o">::</span><span class="n">Entity</span><span class="o">*</span> <span class="n">EntityCast</span> <span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">derivedObject</span> <span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="n">IsPyHorizontal</span><span class="p">(</span><span class="n">derivedObject</span><span class="p">))</span> <span class="k">return</span> <span class="n">PYHORIZONTAL_O</span><span class="p">(</span><span class="n">derivedObject</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">IsPyVertical</span> <span class="p">(</span><span class="n">derivedObject</span><span class="p">))</span> <span class="k">return</span> <span class="n">PYVERTICAL_O</span><span class="p">(</span><span class="n">derivedObject</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">IsPyContact</span> <span class="p">(</span><span class="n">derivedObject</span><span class="p">))</span> <span class="k">return</span> <span class="n">PYCONTACT_O</span><span class="p">(</span><span class="n">derivedObject</span><span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="cp">#endif </span><span class="c1">// Shared Library Code Part (2).</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
</pre></div>
<p></p>
</div>
<div class="section" id="intermediate-class-header">
<h3>4.3 Intermediate Class Header</h3>
<p>Changes from <cite>3.1 Class Associated Header File</cite> are:</p>
<ol class="arabic simple">
<li>As for <tt class="docutils literal">PyEntity</tt>, and because this is still an abstract class,
there is no <tt class="docutils literal">PyComponent_Link()</tt> function.</li>
<li>The definition of the <tt class="docutils literal">PyComponent</tt> <span class="cb">struct</span> is differs. There is
no <tt class="docutils literal">PyObject_HEAD</tt> (it is a Python <em>derived</em> class). The only
field is of the base class type <tt class="docutils literal">PyEntity</tt> and for use with
Coriolis macros, <strong>it must</strong> be named <tt class="docutils literal">_baseObject</tt> (note that
this is <em>not</em> a pointer but a whole object).</li>
</ol>
<div class="highlight"><pre><span></span><span class="cp">#ifndef ISOBAR_PY_COMPONENT_H</span>
<span class="cp">#define ISOBAR_PY_COMPONENT_H</span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyEntity.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/Component.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="n">PyEntity</span> <span class="n">_baseObject</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyComponent</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyTypeObject</span> <span class="n">PyTypeComponent</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyMethodDef</span> <span class="n">PyComponent_Methods</span><span class="p">[];</span>
<span class="k">extern</span> <span class="kt">void</span> <span class="nf">PyComponent_LinkPyType</span> <span class="p">();</span>
<span class="cp">#define IsPyComponent(v) ((v)-&gt;ob_type == &amp;PyTypeComponent)</span>
<span class="cp">#define PYCOMPONENT(v) ((PyComponent*)(v))</span>
<span class="cp">#define PYCOMPONENT_O(v) (static_cast&lt;Component*&gt;(PYCOMPONENT(v)-&gt;_baseObject._object))</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
<span class="cp">#endif</span>
</pre></div>
</div>
<div class="section" id="intermediate-class-file">
<h3>4.4 Intermediate Class File</h3>
<p>Changes from <cite>3.2 Class Associated File</cite> are:</p>
<ol class="arabic simple">
<li>Redefinition of the default macros <tt class="docutils literal">ACCESS_OBJECT</tt> and <tt class="docutils literal">ACCESS_CLASS</tt>.<ul>
<li>The pointer to the C++ encapsulated object (attribute <tt class="docutils literal">_object</tt>) is hold
by the base class <tt class="docutils literal">PyEntity</tt>. The <tt class="docutils literal">ACCESS_OBJECT</tt> macro which is tasked
to give access to that attribute is then <tt class="docutils literal">_baseObject._object</tt> as
<tt class="docutils literal">PyComponent</tt> is a direct derived class of <tt class="docutils literal">PyEntity</tt>.</li>
<li><tt class="docutils literal">ACCESS_CLASS</tt> is similar to <tt class="docutils literal">ACCESS_OBJECT</tt> for accessing the base
class, that is a pointer to <tt class="docutils literal">PyEntity</tt>.</li>
</ul>
</li>
</ol>
<p></p>
<ol class="arabic simple" start="2">
<li>For defining the <tt class="docutils literal">PyTypeComponent</tt> Python type, we call a yet different
macro: <tt class="docutils literal">PyTypeInheritedObjectDefinitions()</tt>, dedicated to derived classes.
For this this macro we need to give as argument the derived class and the
base class.</li>
</ol>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyComponent.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyNet.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#undef ACCESS_OBJECT</span>
<span class="cp">#undef ACCESS_CLASS</span>
<span class="cp">#define ACCESS_OBJECT _baseObject._object</span>
<span class="cp">#define ACCESS_CLASS(_pyObject) &amp;(_pyObject-&gt;_baseObject)</span>
<span class="cp">#define METHOD_HEAD(function) GENERIC_METHOD_HEAD(Component,component,function)</span>
<span class="cp">#if defined(__PYTHON_MODULE__)</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyComponent_getX</span><span class="p">,</span><span class="n">getX</span><span class="p">,</span><span class="n">PyComponent</span><span class="p">,</span><span class="n">Component</span><span class="p">)</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyComponent_getY</span><span class="p">,</span><span class="n">getY</span><span class="p">,</span><span class="n">PyComponent</span><span class="p">,</span><span class="n">Component</span><span class="p">)</span>
<span class="n">DBoDestroyAttribute</span><span class="p">(</span><span class="n">PyComponent_destroy</span><span class="p">,</span><span class="n">PyComponent</span><span class="p">)</span>
<span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">PyComponent_getNet</span> <span class="p">(</span> <span class="n">PyComponent</span> <span class="o">*</span><span class="n">self</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Net</span><span class="o">*</span> <span class="n">net</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="nf">METHOD_HEAD</span><span class="p">(</span> <span class="s">&quot;Component.getNet()&quot; )</span>
<span class="n">net</span> <span class="o">=</span> <span class="n">component</span><span class="o">-&gt;</span><span class="n">getNet</span><span class="p">(</span> <span class="p">);</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="nf">PyNet_Link</span><span class="p">(</span> <span class="n">net</span> <span class="p">);</span>
<span class="p">}</span>
<span class="n">PyMethodDef</span> <span class="n">PyComponent_Methods</span><span class="p">[]</span> <span class="o">=</span>
<span class="p">{</span> <span class="p">{</span> <span class="s">&quot;getX&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyComponent_getX</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the Component X value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getY&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyComponent_getY</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the Component Y value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getNet&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyComponent_getNet</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Returns the net owning the component.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;destroy&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyComponent_destroy</span><span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;destroy associated hurricane object, the python object remains.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span><span class="nb">NULL</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">}</span> <span class="cm">/* sentinel */</span>
<span class="p">};</span>
<span class="n">DBoDeleteMethod</span><span class="p">(</span><span class="n">Component</span><span class="p">)</span>
<span class="n">PyTypeObjectLinkPyType</span><span class="p">(</span><span class="n">Component</span><span class="p">)</span>
<span class="cp">#else </span><span class="c1">// Python Module Code Part.</span>
<span class="n">PyTypeInheritedObjectDefinitions</span><span class="p">(</span><span class="n">Component</span><span class="p">,</span> <span class="n">Entity</span><span class="p">)</span>
<span class="cp">#endif </span><span class="c1">// Shared Library Code Part.</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
</pre></div>
</div>
<div class="section" id="terminal-class-header">
<h3>4.5 Terminal Class Header</h3>
<p>The contents of this file is almost identical to <a class="reference internal" href="#intermediate-class-header">4.3 Intermediate Class Header</a>,
save for the presence of a <tt class="docutils literal">PyContact_Link()</tt> function. She is present
at this level because the class is a concrete one and can be instanciated.</p>
<div class="highlight"><pre><span></span><span class="cp">#ifndef ISOBAR_PY_CONTACT_H</span>
<span class="cp">#define ISOBAR_PY_CONTACT_H</span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyComponent.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/Contact.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="n">PyComponent</span> <span class="n">_baseObject</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyContact</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyTypeObject</span> <span class="n">PyTypeContact</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyMethodDef</span> <span class="n">PyContact_Methods</span><span class="p">[];</span>
<span class="k">extern</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyContact_Link</span> <span class="p">(</span> <span class="n">Hurricane</span><span class="o">::</span><span class="n">Contact</span><span class="o">*</span> <span class="n">object</span> <span class="p">);</span>
<span class="k">extern</span> <span class="kt">void</span> <span class="nf">PyContact_LinkPyType</span> <span class="p">();</span>
<span class="cp">#define IsPyContact(v) ( (v)-&gt;ob_type == &amp;PyTypeContact )</span>
<span class="cp">#define PYCONTACT(v) ( (PyContact*)(v) )</span>
<span class="cp">#define PYCONTACT_O(v) ( PYCONTACT(v)-&gt;_baseObject._baseObject._object )</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
<span class="cp">#endif </span><span class="c1">// ISOBAR_PY_CONTACT_H</span>
</pre></div>
</div>
<div class="section" id="terminal-class-file">
<h3>4.6 Terminal Class File</h3>
<p>Changes from <a class="reference internal" href="#intermediate-class-file">4.4 Intermediate Class File</a> are:</p>
<ol class="arabic simple">
<li>As previously, we have to redefine the macros <tt class="docutils literal">ACCESS_OBJECT</tt> and <tt class="docutils literal">ACCESS_CLASS</tt>.
But, as we are one level deeper into the hierarchy, one more level of
indirection using <tt class="docutils literal">_baseObject</tt> must be used.<ul>
<li><tt class="docutils literal">ACCESS_OBJECT</tt> becomes <tt class="docutils literal">_baseObject._baseObject._object</tt>.</li>
<li><tt class="docutils literal">ACCESS_CLASS</tt> becomes <tt class="docutils literal"><span class="pre">&amp;(_pyObject-&gt;_baseObject._baseObject)</span></tt>.</li>
</ul>
</li>
<li>For defining the <tt class="docutils literal">PyTypeContact</tt> Python type, we call again
<tt class="docutils literal">PyTypeInheritedObjectDefinitions()</tt>. It is the same whether the class is
terminal or not.</li>
<li>And, this time, as the Python class is concrete, we call the macro
<tt class="docutils literal">DBoLinkCreateMethod()</tt> to create the <tt class="docutils literal">PyContact_Link()</tt> function.</li>
</ol>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyContact.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#undef ACCESS_OBJECT</span>
<span class="cp">#undef ACCESS_CLASS</span>
<span class="cp">#define ACCESS_OBJECT _baseObject._baseObject._object</span>
<span class="cp">#define ACCESS_CLASS(_pyObject) &amp;(_pyObject-&gt;_baseObject._baseObject)</span>
<span class="cp">#define METHOD_HEAD(function) GENERIC_METHOD_HEAD(Contact,contact,function)</span>
<span class="cp">#if defined(__PYTHON_MODULE__)</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyContact_getWidth</span> <span class="p">,</span> <span class="n">getWidth</span> <span class="p">,</span> <span class="n">PyContact</span><span class="p">,</span><span class="n">Contact</span><span class="p">)</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyContact_getHeight</span><span class="p">,</span> <span class="n">getHeight</span><span class="p">,</span> <span class="n">PyContact</span><span class="p">,</span><span class="n">Contact</span><span class="p">)</span>
<span class="n">DBoDestroyAttribute</span><span class="p">(</span><span class="n">PyContact_destroy</span><span class="p">,</span> <span class="n">PyContact</span><span class="p">)</span>
<span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">PyContact_create</span> <span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Contact</span><span class="o">*</span> <span class="n">contact</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="c1">// Usual signature then arguments parsing.</span>
<span class="n">HCATCH</span>
<span class="k">return</span> <span class="n">PyContact_Link</span><span class="p">(</span><span class="n">contact</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">PyMethodDef</span> <span class="n">PyContact_Methods</span><span class="p">[]</span> <span class="o">=</span>
<span class="p">{</span> <span class="p">{</span> <span class="s">&quot;create&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyContact_create</span> <span class="p">,</span> <span class="n">METH_VARARGS</span><span class="o">|</span><span class="n">METH_STATIC</span>
<span class="p">,</span> <span class="s">&quot;Create a new Contact.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;destroy&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyContact_destroy</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Destroy associated hurricane object, the python object remains.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getWidth&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyContact_getWidth</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the contact width.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getHeight&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyContact_getHeight</span><span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the contact height.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span><span class="nb">NULL</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">}</span> <span class="cm">/* sentinel */</span>
<span class="p">};</span>
<span class="n">DBoDeleteMethod</span><span class="p">(</span><span class="n">Contact</span><span class="p">)</span>
<span class="n">PyTypeObjectLinkPyType</span><span class="p">(</span><span class="n">Contact</span><span class="p">)</span>
<span class="cp">#else </span><span class="c1">// Python Module Code Part.</span>
<span class="n">DBoLinkCreateMethod</span><span class="p">(</span><span class="n">Contact</span><span class="p">)</span>
<span class="n">PyTypeInheritedObjectDefinitions</span><span class="p">(</span><span class="n">Contact</span><span class="p">,</span> <span class="n">Component</span><span class="p">)</span>
<span class="cp">#endif </span><span class="c1">// Shared Library Code Part.</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
</pre></div>
</div>
<div class="section" id="python-module">
<h3>4.8 Python Module</h3>
<div class="highlight"><pre><span></span><span class="n">DL_EXPORT</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span> <span class="n">initHurricane</span> <span class="p">()</span>
<span class="p">{</span>
<span class="n">PyEntity_LinkPyType</span><span class="p">();</span> <span class="c1">// step 1.</span>
<span class="n">PyComponent_LinkPyType</span><span class="p">();</span>
<span class="n">PyContact_LinkPyType</span><span class="p">();</span>
<span class="n">PYTYPE_READY</span><span class="p">(</span> <span class="n">Entity</span> <span class="p">)</span> <span class="c1">// step 2.</span>
<span class="n">PYTYPE_READY_SUB</span><span class="p">(</span> <span class="n">Component</span><span class="p">,</span> <span class="n">Entity</span> <span class="p">)</span>
<span class="n">PYTYPE_READY_SUB</span><span class="p">(</span> <span class="n">Contact</span> <span class="p">,</span> <span class="n">Component</span> <span class="p">)</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">addType</span><span class="p">(</span> <span class="s">&quot;ent&quot;</span> <span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeEntity</span> <span class="p">,</span> <span class="s">&quot;&lt;Entity&gt;&quot;</span> <span class="p">,</span> <span class="nb">false</span> <span class="p">);</span> <span class="c1">// step 3.</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">addType</span><span class="p">(</span> <span class="s">&quot;comp&quot;</span> <span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeComponent</span><span class="p">,</span> <span class="s">&quot;&lt;Component&gt;&quot;</span><span class="p">,</span> <span class="nb">false</span><span class="p">,</span> <span class="s">&quot;ent&quot;</span> <span class="p">);</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">addType</span><span class="p">(</span> <span class="s">&quot;contact&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypeContact</span> <span class="p">,</span> <span class="s">&quot;&lt;Contact&gt;&quot;</span> <span class="p">,</span> <span class="nb">false</span><span class="p">,</span> <span class="s">&quot;comp&quot;</span> <span class="p">);</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">module</span> <span class="o">=</span> <span class="n">Py_InitModule</span><span class="p">(</span> <span class="s">&quot;Hurricane&quot;</span><span class="p">,</span> <span class="n">PyHurricane_Methods</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">module</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;[ERROR]</span><span class="se">\n</span><span class="s">&quot;</span>
<span class="o">&lt;&lt;</span> <span class="s">&quot; Failed to initialize Hurricane module.&quot;</span> <span class="o">&lt;&lt;</span> <span class="n">endl</span><span class="p">;</span>
<span class="k">return</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">Py_INCREF</span><span class="p">(</span> <span class="o">&amp;</span><span class="n">PyTypeContact</span> <span class="p">);</span> <span class="c1">// step 4.</span>
<span class="n">PyModule_AddObject</span><span class="p">(</span> <span class="n">module</span><span class="p">,</span> <span class="s">&quot;Contact&quot;</span><span class="p">,</span> <span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)</span><span class="o">&amp;</span><span class="n">PyTypeContact</span> <span class="p">);</span> <span class="c1">// step 4.</span>
<span class="p">}</span>
</pre></div>
<!-- -*- Mode: rst -*- -->
</div>
</div>
<div class="section" id="case-3-non-dbo-standalone-classe">
<h2><a class="toc-backref" href="#id11">5. Case 3 - Non-DBo Standalone Classe</a></h2>
<p>Let's have a look at the encapsulation of <tt class="docutils literal"><span class="pre">Hurricane::Point</span></tt>.</p>
<p>Non-BDo derived classes do not support the bi-directionnal communication.
So each Python object is associated with one C++ object. The C++ object
is created and deleted along with the Python one. This behavior implies
that the C++ object is <em>copy constructible</em> (which should be the case).</p>
<div class="section" id="class-header">
<h3>5.1 Class Header</h3>
<p>Changes from <cite>3.1 Class Associated Header File</cite>:</p>
<ul class="simple">
<li>There is no <tt class="docutils literal">PyPoint_Link()</tt> function, as it's related to the
bi-directional communication mechanism.</li>
</ul>
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last"><strong>About the _object attribute</strong> of the PyPoint. As the C++ object life span
(<tt class="docutils literal">Point</tt>) is linked to the Python (<tt class="docutils literal">PyPoint</tt>) one, we may have used a
value instead of a pointer. It is best to keep a pointer as the macros
written for <tt class="docutils literal">DBo</tt> derived classes will remain usables.</p>
</div>
<div class="highlight"><pre><span></span><span class="cp">#ifndef ISOBAR_PY_POINT_H</span>
<span class="cp">#define ISOBAR_PY_POINT_H</span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyHurricane.h&quot;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&quot;hurricane/Point.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="n">PyObject_HEAD</span>
<span class="n">Hurricane</span><span class="o">::</span><span class="n">Point</span><span class="o">*</span> <span class="n">_object</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyPoint</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyTypeObject</span> <span class="n">PyTypePoint</span><span class="p">;</span>
<span class="k">extern</span> <span class="n">PyMethodDef</span> <span class="n">PyPoint_Methods</span><span class="p">[];</span>
<span class="k">extern</span> <span class="kt">void</span> <span class="nf">PyPoint_LinkPyType</span><span class="p">();</span>
<span class="cp">#define IsPyPoint(v) ( (v)-&gt;ob_type == &amp;PyTypePoint )</span>
<span class="cp">#define PYPOINT(v) ( (PyPoint*)(v) )</span>
<span class="cp">#define PYPOINT_O(v) ( PYPOINT(v)-&gt;_object )</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
<span class="cp">#endif </span><span class="c1">// ISOBAR_PY_POINT_H</span>
</pre></div>
<p></p>
</div>
<div class="section" id="class-file">
<h3>5.2 Class File</h3>
<p>Changes from <cite>3.2 Class Associated File</cite>:</p>
<ul class="simple">
<li>As there is no <tt class="docutils literal">PyPoint_Link()</tt> function, there is no call to any
flavor of the <tt class="docutils literal">DBoLinkcreatemethod()</tt> macro (obvious as it's <em>not</em>
a <tt class="docutils literal">DBo</tt>).</li>
<li>To use the standard Python constructor, we have to define <tt class="docutils literal">PyPoint_NEW()</tt>
and <tt class="docutils literal">PyPoint_Init()</tt> functions, I'm not absolutely certain that the later
needs to be defined (that part is still not clear to me from the Python doc).</li>
<li>As it's not a <tt class="docutils literal">DBo</tt> there is no <tt class="docutils literal">destroy()</tt> method, so no call to
<tt class="docutils literal">DirectDestroyMethod()</tt></li>
<li>Lastly, as this object has a <tt class="docutils literal">PyPoint_NEW()</tt> (field <tt class="docutils literal">tp_new</tt>) and
a <tt class="docutils literal">PyPoint_Init()</tt> (field <tt class="docutils literal">tp_init</tt>) we have to use the macro
<tt class="docutils literal">PyTypeObjectLinkPyTypeNewInit()</tt> to define <tt class="docutils literal">PyPoint_LinkPyType()</tt>.</li>
</ul>
<div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&quot;hurricane/isobar/PyPoint.h&quot;</span><span class="cp"></span>
<span class="k">namespace</span> <span class="n">Isobar</span> <span class="p">{</span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">Hurricane</span><span class="p">;</span>
<span class="k">extern</span> <span class="s">&quot;C&quot;</span> <span class="p">{</span>
<span class="cp">#define METHOD_HEAD(function) GENERIC_METHOD_HEAD(Point,point,function)</span>
<span class="cp">#if defined(__PYTHON_MODULE__)</span>
<span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">PyPoint_NEW</span> <span class="p">(</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">module</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Point</span><span class="o">*</span> <span class="n">point</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">HTRY</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">arg0</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">arg1</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">__cs</span><span class="p">.</span><span class="n">init</span><span class="p">(</span> <span class="s">&quot;Point.Point&quot;</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">not</span> <span class="n">PyArg_ParseTuple</span><span class="p">(</span> <span class="n">args</span><span class="p">,</span><span class="s">&quot;|O&amp;O&amp;:Point.Point&quot;</span>
<span class="p">,</span> <span class="n">Converter</span><span class="p">,</span><span class="o">&amp;</span><span class="n">arg0</span>
<span class="p">,</span> <span class="n">Converter</span><span class="p">,</span><span class="o">&amp;</span><span class="n">arg1</span> <span class="p">))</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span> <span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Point constructor.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">if</span> <span class="p">(</span><span class="n">__cs</span><span class="p">.</span><span class="n">getObjectIds</span><span class="p">()</span> <span class="o">==</span> <span class="s">&quot;&quot;</span><span class="p">)</span>
<span class="p">{</span> <span class="n">point</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Point</span><span class="p">());</span> <span class="p">}</span>
<span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">__cs</span><span class="p">.</span><span class="n">getObjectIds</span><span class="p">()</span> <span class="o">==</span> <span class="s">&quot;:point&quot;</span><span class="p">)</span>
<span class="p">{</span> <span class="n">point</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Point</span><span class="p">(</span> <span class="o">*</span><span class="n">PYPOINT_O</span><span class="p">(</span><span class="n">arg0</span><span class="p">)</span> <span class="p">);</span> <span class="p">}</span>
<span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">__cs</span><span class="p">.</span><span class="n">getObjectIds</span><span class="p">()</span> <span class="o">==</span> <span class="s">&quot;:int:int&quot;</span><span class="p">)</span>
<span class="p">{</span> <span class="n">point</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Point</span><span class="p">(</span> <span class="n">PyAny_AsLong</span><span class="p">(</span><span class="n">arg0</span><span class="p">),</span> <span class="n">PyAny_AsLong</span><span class="p">(</span><span class="n">arg1</span><span class="p">)</span> <span class="p">);</span> <span class="p">}</span>
<span class="k">else</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span> <span class="p">(</span> <span class="n">ConstructorError</span>
<span class="p">,</span> <span class="s">&quot;invalid number of parameters for Point constructor.&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">PyPoint</span><span class="o">*</span> <span class="n">pyPoint</span> <span class="o">=</span> <span class="n">PyObject_NEW</span><span class="p">(</span> <span class="n">PyPoint</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">PyTypePoint</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">pyPoint</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span> <span class="k">delete</span> <span class="n">point</span><span class="p">;</span> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span> <span class="p">}</span>
<span class="n">pyPoint</span><span class="o">-&gt;</span><span class="n">_object</span> <span class="o">=</span> <span class="n">point</span><span class="p">;</span>
<span class="n">HCATCH</span>
<span class="nf">return</span> <span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)</span><span class="n">pyPoint</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">static</span> <span class="kt">int</span> <span class="n">PyPoint_Init</span> <span class="p">(</span> <span class="n">PyPoint</span><span class="o">*</span> <span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">args</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">kwargs</span> <span class="p">)</span>
<span class="p">{</span> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span> <span class="p">}</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_getX</span><span class="p">,</span><span class="n">getX</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
<span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_getY</span><span class="p">,</span><span class="n">getY</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
<span class="n">DirectSetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_SetX</span><span class="p">,</span><span class="n">setX</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
<span class="n">DirectSetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_SetY</span><span class="p">,</span><span class="n">setY</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
<span class="n">PyMethodDef</span> <span class="n">PyPoint_Methods</span><span class="p">[]</span> <span class="o">=</span>
<span class="p">{</span> <span class="p">{</span> <span class="s">&quot;getX&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyPoint_getX</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the Point X value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;getY&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyPoint_getY</span> <span class="p">,</span> <span class="n">METH_NOARGS</span>
<span class="p">,</span> <span class="s">&quot;Return the Point Y value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;setX&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyPoint_SetX</span> <span class="p">,</span> <span class="n">METH_VARARGS</span>
<span class="p">,</span> <span class="s">&quot;Modify the Point X value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span> <span class="s">&quot;setY&quot;</span> <span class="p">,</span> <span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">PyPoint_SetY</span> <span class="p">,</span> <span class="n">METH_VARARGS</span>
<span class="p">,</span> <span class="s">&quot;Modify the Point Y value.&quot;</span> <span class="p">}</span>
<span class="p">,</span> <span class="p">{</span><span class="nb">NULL</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">}</span> <span class="cm">/* sentinel */</span>
<span class="p">};</span>
<span class="n">DirectDeleteMethod</span><span class="p">(</span><span class="n">PyPoint_DeAlloc</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">)</span>
<span class="n">PyTypeObjectLinkPyTypeNewInit</span><span class="p">(</span><span class="n">Point</span><span class="p">)</span>
<span class="cp">#else </span><span class="c1">// Python Module Code Part.</span>
<span class="n">PyTypeObjectDefinitions</span><span class="p">(</span><span class="n">Point</span><span class="p">)</span>
<span class="cp">#endif </span><span class="c1">// Shared Library Code Part.</span>
<span class="p">}</span> <span class="c1">// extern &quot;C&quot;.</span>
<span class="p">}</span> <span class="c1">// Isobar namespace.</span>
</pre></div>
</div>
<div class="section" id="id6">
<h3>5.2 Class File</h3>
<p>To put it bluntly, there is no difference in the Python module for
a standalone <tt class="docutils literal">DBo</tt> class and a non-<tt class="docutils literal">DBo</tt> class.</p>
<!-- -*- Mode: rst -*- -->
</div>
</div>
<div class="section" id="encapsulating-dbu">
<h2><a class="toc-backref" href="#id12">6. Encapsulating DbU</a></h2>
<p>While <tt class="docutils literal"><span class="pre">Hurricane::DbU</span></tt> is a class, the <tt class="docutils literal"><span class="pre">Hurricane::DbU::Unit</span></tt> is only
a <tt class="docutils literal">typedef</tt> over <tt class="docutils literal">uint64_t</tt>. The <tt class="docutils literal">DbU</tt> class only provides a set of
static methods to manipulate and convert to and from other units.
At Python level, <tt class="docutils literal"><span class="pre">DbU::Unit</span></tt> will be stored in plain <tt class="docutils literal">long long</tt>.</p>
<p>When a <tt class="docutils literal"><span class="pre">DbU::Unit</span></tt> argument is expected in a Python functions, just use
the <tt class="docutils literal"><span class="pre">DbU::Unit</span>&nbsp; PyAny_AsLong( PyObject* )</tt> function to convert it.</p>
<p>For example, if we explicit the expension of:</p>
<div class="highlight"><pre><span></span><span class="n">DirectSetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_SetX</span><span class="p">,</span><span class="n">setX</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
</pre></div>
<p></p>
<p>We would get:</p>
<div class="highlight"><pre><span></span><span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyPoint_setX</span> <span class="p">(</span> <span class="n">PyPoint</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Point</span><span class="o">*</span> <span class="n">cobject</span> <span class="o">=</span> <span class="k">static_cast</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">*&gt;</span><span class="p">(</span> <span class="n">self</span><span class="o">-&gt;</span><span class="n">_object</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">cobject</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ProxyError</span>
<span class="p">,</span> <span class="s">&quot;Attempt to call Point.setX() on an unbound Hurricane object&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">HTRY</span>
<span class="n">PyObject</span><span class="o">*</span> <span class="n">arg0</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">not</span> <span class="n">PyArg_ParseTuple</span><span class="p">(</span> <span class="n">args</span><span class="p">,</span> <span class="s">&quot;O:Point.setX()&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">arg0</span> <span class="p">))</span>
<span class="k">return</span> <span class="p">(</span> <span class="nb">NULL</span> <span class="p">);</span>
<span class="n">cobject</span><span class="o">-&gt;</span><span class="n">setX</span><span class="p">(</span> <span class="n">Isobar</span><span class="o">::</span><span class="n">PyAny_AsLong</span><span class="p">(</span><span class="n">arg0</span><span class="p">)</span> <span class="p">);</span>
<span class="n">HCATCH</span>
<span class="n">Py_RETURN_NONE</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
<p>For the other way around, use <tt class="docutils literal">PyObject* PyDbU_FromLong( <span class="pre">DbU::Unit</span> )</tt>.</p>
<div class="highlight"><pre><span></span><span class="n">DirectGetLongAttribute</span><span class="p">(</span><span class="n">PyPoint_GetX</span><span class="p">,</span><span class="n">getX</span><span class="p">,</span><span class="n">PyPoint</span><span class="p">,</span><span class="n">Point</span><span class="p">)</span>
</pre></div>
<p>We would get:</p>
<div class="highlight"><pre><span></span><span class="k">static</span> <span class="n">PyObject</span><span class="o">*</span> <span class="nf">PyPoint_GetX</span> <span class="p">(</span> <span class="n">PyPoint</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span><span class="o">*</span> <span class="n">args</span> <span class="p">)</span>
<span class="p">{</span>
<span class="n">Point</span><span class="o">*</span> <span class="n">cobject</span> <span class="o">=</span> <span class="k">static_cast</span><span class="o">&lt;</span><span class="n">Point</span><span class="o">*&gt;</span><span class="p">(</span> <span class="n">self</span><span class="o">-&gt;</span><span class="n">_object</span> <span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">cobject</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="n">PyErr_SetString</span><span class="p">(</span> <span class="n">ProxyError</span>
<span class="p">,</span> <span class="s">&quot;Attempt to call Point.getX() on an unbound Hurricane object&quot;</span> <span class="p">);</span>
<span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">return</span> <span class="n">Isobar</span><span class="o">::</span><span class="n">PyDbU_FromLong</span><span class="p">(</span><span class="n">cobject</span><span class="o">-&gt;</span><span class="n">getX</span><span class="p">());</span>
<span class="p">}</span>
</pre></div>
<!-- -*- Mode: rst -*- -->
</div>
<div class="section" id="no-c-hurricane-name-encapsulation">
<h2><a class="toc-backref" href="#id13">7. No C++ Hurricane::Name encapsulation</a></h2>
<p>To be written.</p>
</div>
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