Re-implement Python -fastproxy option.
The previous implementation failed with Python 3 and abstract base clases. The new implementation replaces the Python 2 implementation using new.instancemethod with C API PyMethod_New to match the equivalent Python 3 implementation which uses PyInstanceMethod_New. Closes #1310
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William S Fulton
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6 changed files with 144 additions and 32 deletions
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@ -7,6 +7,16 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
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Version 4.0.0 (in progress)
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===========================
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2018-08-18: wsfulton
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[Python] #1310 Re-implement Python -fastproxy option.
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The previous implementation failed with Python 3 and abstract base clases.
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The new implementation replaces the Python 2 implementation using
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new.instancemethod with the C API PyMethod_New to match the equivalent Python 3
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implementation which uses PyInstanceMethod_New.
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The new approach runs slightly faster. See #1310.
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2018-08-12: gmazzamuto
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[Python] #1283 Update pybuffer.i library to use new-style Python buffer C API.
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@ -1642,6 +1642,10 @@
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<li><a href="Python.html#Python_nn42">Adding additional Python code</a>
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<li><a href="Python.html#Python_nn43">Class extension with %extend</a>
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<li><a href="Python.html#Python_nn44">Exception handling with %exception</a>
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<li><a href="Python.html#Python_optimization">Optimization options</a>
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<ul>
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<li><a href="Python.html#Python_fastproxy">-fastproxy</a>
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</ul>
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</ul>
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<li><a href="Python.html#Python_nn45">Tips and techniques</a>
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<ul>
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@ -71,6 +71,10 @@
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<li><a href="#Python_nn42">Adding additional Python code</a>
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<li><a href="#Python_nn43">Class extension with %extend</a>
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<li><a href="#Python_nn44">Exception handling with %exception</a>
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<li><a href="#Python_optimization">Optimization options</a>
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<ul>
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<li><a href="#Python_fastproxy">-fastproxy</a>
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</ul>
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</ul>
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<li><a href="#Python_nn45">Tips and techniques</a>
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<ul>
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@ -3797,6 +3801,99 @@ The language-independent <tt>exception.i</tt> library file can also be used
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to raise exceptions. See the <a href="Library.html#Library">SWIG Library</a> chapter.
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</p>
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<H3><a name="Python_optimization">38.6.5 Optimization options</a></H3>
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<H4><a name="Python_fastproxy">38.6.5.1 -fastproxy</a></H4>
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<p>
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The <tt>-fastproxy</tt> command line option enables faster method calling as the call is made directly into the C/C++ layer rather than going through a method wrapper.
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</p>
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<p>
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Consider wrapping a C++ class:
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</p>
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<div class="code">
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<pre>
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struct Go {
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void callme0() {}
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void callme4(int a, int b, int c, int d) {}
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void callme8(double a, double b, double c, double d, double e, double f, double g, double i) {}
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};
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</pre>
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</div>
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<p>
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The default generated proxy class is:
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</p>
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<div class="targetlang">
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<pre>
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class Go(object):
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def callme0(self):
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return _example.Go_callme0(self)
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def callme4(self, a, b, c, d):
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return _example.Go_callme4(self, a, b, c, d)
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def callme8(self, a, b, c, d, e, f, g, i):
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return _example.Go_callme8(self, a, b, c, d, e, f, g, i)
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...
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</pre>
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</div>
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<p>
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The generated code when using <tt>-fastproxy</tt> is:
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</p>
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<div class="targetlang">
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<pre>
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%module example
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class Go(_object):
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callme0 = _swig_new_instance_method(_example.Go_callme0)
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callme4 = _swig_new_instance_method(_example.Go_callme4)
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callme8 = _swig_new_instance_method(_example.Go_callme8)
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...
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</pre>
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</div>
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<p>
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where <tt>_swig_new_instance_method</tt> adds the method to the proxy class via C API calls.
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The overhead calling into C/C++ from Python is reduced slightly using <tt>-fastproxy</tt>.
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Below are some timings in microseconds calling the 3 functions in the example above:
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</p>
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<table summary="Python fastproxy performance">
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<tr>
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<th>Method name</th>
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<th>Without -proxy</th>
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<th>With -proxy</th>
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</tr>
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<tr>
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<td>callme0</td>
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<td>0.57</td>
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<td>0.48</td>
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</tr>
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<tr>
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<td>callme4</td>
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<td>0.64</td>
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<td>0.54</td>
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</tr>
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<tr>
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<td>callme8</td>
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<td>0.73</td>
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<td>0.57</td>
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</tr>
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</table>
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<p>
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Although the <tt>-fastproxy</tt> option results in faster code, the generated proxy code is not as user-friendly
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as docstring/doxygen comments and functions with default values are not visible in the generated python proxy class.
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</p>
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<H2><a name="Python_nn45">38.7 Tips and techniques</a></H2>
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@ -13,15 +13,20 @@ def check(got, expected, expected_builtin=None, skip=False):
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def is_new_style_class(cls):
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return hasattr(cls, "__class__")
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def is_fastproxy(module):
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return "new_instancemethod" in module
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def is_fastproxy():
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fastproxy = True
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try:
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from autodoc import _swig_new_instance_method
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except ImportError:
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fastproxy = False
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return fastproxy
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if not is_new_style_class(A):
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# Missing static methods make this hard to test... skip if -classic is
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# used!
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sys.exit(0)
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if is_fastproxy(dir()):
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if is_fastproxy():
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# Detect when -fastproxy is specified and skip test as it changes the function names making it
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# hard to test... skip until the number of options are reduced in SWIG-3.1 and autodoc is improved
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sys.exit(0)
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@ -29,17 +29,14 @@ typedef struct swig_const_info {
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* Wrapper of PyInstanceMethod_New() used in Python 3
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* It is exported to the generated module, used for -fastproxy
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* ----------------------------------------------------------------------------- */
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#if PY_VERSION_HEX >= 0x03000000
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SWIGRUNTIME PyObject* SWIG_PyInstanceMethod_New(PyObject *SWIGUNUSEDPARM(self), PyObject *func)
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{
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#if PY_VERSION_HEX >= 0x03000000
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return PyInstanceMethod_New(func);
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}
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#else
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SWIGRUNTIME PyObject* SWIG_PyInstanceMethod_New(PyObject *SWIGUNUSEDPARM(self), PyObject *SWIGUNUSEDPARM(func))
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{
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return NULL;
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}
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return PyMethod_New(func, NULL, NULL);
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#endif
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}
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#ifdef __cplusplus
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}
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@ -825,18 +825,8 @@ public:
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}
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Printv(default_import_code, "\nfrom sys import version_info as _swig_python_version_info\n", NULL);
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if (!builtin && fastproxy) {
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Printv(default_import_code, "if _swig_python_version_info >= (3, 0, 0):\n", NULL);
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Printf(default_import_code, tab4 "new_instancemethod = lambda func, inst, cls: %s.SWIG_PyInstanceMethod_New(func)\n", module);
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Printv(default_import_code, "elif _swig_python_version_info >= (2, 7, 0):\n", NULL);
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Printv(default_import_code, tab4, "from new import instancemethod as new_instancemethod\n", NULL);
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Printv(default_import_code, "else:\n", NULL);
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Printv(default_import_code, tab4, "raise RuntimeError('Python 2.7 or later required')\n", NULL);
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} else {
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Printv(default_import_code, "if _swig_python_version_info < (2, 7, 0):\n", NULL);
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Printv(default_import_code, tab4, "raise RuntimeError('Python 2.7 or later required')\n", NULL);
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}
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Printv(default_import_code, "if _swig_python_version_info < (2, 7, 0):\n", NULL);
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Printv(default_import_code, tab4, "raise RuntimeError('Python 2.7 or later required')\n", NULL);
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/* Import the C-extension module. This should be a relative import,
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* since the shadow module may also have been imported by a relative
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@ -897,6 +887,11 @@ public:
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defined in this module (try both Python 3 and Python 2 names) */
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Printv(f_shadow, "try:\n", tab4, "import builtins as __builtin__\n", "except ImportError:\n", tab4, "import __builtin__\n", NULL);
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if (!builtin && fastproxy) {
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Printf(f_shadow, "\n");
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Printf(f_shadow, "_swig_new_instance_method = %s.SWIG_PyInstanceMethod_New\n", module);
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}
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/* if (!modern) */
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/* always needed, a class can be forced to be no-modern, such as an exception */
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{
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@ -4682,32 +4677,36 @@ public:
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}
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/* Now emit methods */
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if (!builtin)
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if (!builtin) {
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Printv(f_shadow_file, f_shadow, NIL);
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if (fastproxy) {
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Printf(f_shadow_file, "\n");
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List *shadow_list = Getattr(n, "shadow_methods");
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for (int i = 0; i < Len(shadow_list); ++i) {
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String *symname = Getitem(shadow_list, i);
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Printf(f_shadow_file, tab4);
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Printf(f_shadow_file, "%s = _swig_new_instance_method(%s.%s)\n", symname, module, Swig_name_member(NSPACE_TODO, class_name, symname));
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}
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}
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}
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/* Now the Ptr class */
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if (classptr && !builtin) {
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Printv(f_shadow_file, "\nclass ", class_name, "Ptr(", class_name, "):\n", tab4, "def __init__(self, this):\n", NIL);
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if (!modern) {
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Printv(f_shadow_file,
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tab8, "try:\n", tab8, tab4, "self.this.append(this)\n",
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tab8, "except __builtin__.Exception:\n", tab8, tab4, "self.this = this\n", tab8, "self.this.own(0)\n", tab8, "self.__class__ = ", class_name, "\n\n", NIL);
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tab8, "except __builtin__.Exception:\n", tab8, tab4, "self.this = this\n", tab8, "self.this.own(0)\n", tab8, "self.__class__ = ", class_name, "\n", NIL);
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} else {
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Printv(f_shadow_file,
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tab8, "try:\n", tab8, tab4, "self.this.append(this)\n",
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tab8, "except __builtin__.Exception:\n", tab8, tab4, "self.this = this\n", tab8, "self.this.own(0)\n", tab8, "self.__class__ = ", class_name, "\n\n", NIL);
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tab8, "except __builtin__.Exception:\n", tab8, tab4, "self.this = this\n", tab8, "self.this.own(0)\n", tab8, "self.__class__ = ", class_name, "\n", NIL);
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}
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}
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if (!builtin) {
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if (fastproxy) {
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List *shadow_list = Getattr(n, "shadow_methods");
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for (int i = 0; i < Len(shadow_list); ++i) {
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String *symname = Getitem(shadow_list, i);
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Printf(f_shadow_file, "%s.%s = new_instancemethod(%s.%s, None, %s)\n", class_name, symname, module, Swig_name_member(NSPACE_TODO, class_name, symname),
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class_name);
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}
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}
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Printf(f_shadow_file, "\n");
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Printf(f_shadow_file, "# Register %s in %s:\n", class_name, module);
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Printf(f_shadow_file, "%s.%s_swigregister(%s)\n", module, class_name, class_name);
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}
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