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63 lines
2.3 KiB
63 lines
2.3 KiB
Using the C API when Embedding
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==============================
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The :ref:`C API <ref-c-api>` is intended to be called from handwritten code in
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SIP generated modules. However it is also often necessary to call it from C or
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C++ applications that embed the Python interpreter and need to pass C or C++
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instances between the application and the interpreter.
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The API is exported by the SIP module as a ``sipAPIDef`` data structure
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containing a set of function pointers. The data structure is defined in the
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SIP header file ``sip.h``. The data structure is wrapped as a Python
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``PyCObject`` object and is referenced by the name ``_C_API`` in the SIP
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module dictionary.
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Each member of the data structure is a pointer to one of the functions of the
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SIP API. The name of the member can be derived from the function name by
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replacing the ``sip`` prefix with ``api`` and converting each word in the
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name to lower case and preceding it with an underscore. For example:
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``sipExportSymbol`` becomes ``api_export_symbol``
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``sipWrapperCheck`` becomes ``api_wrapper_check``
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Note that the type objects that SIP generates for a wrapped module (see
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:ref:`ref-type-structures`, :ref:`ref-enum-type-objects` and
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:ref:`ref-exception-objects`) cannot be refered to directly and must be
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obtained using the :cfunc:`sipFindType()` function. Of course, the
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corresponding modules must already have been imported into the interpreter.
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The following code fragment shows how to get a pointer to the ``sipAPIDef``
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data structure::
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#include <sip.h>
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const sipAPIDef *get_sip_api()
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{
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PyObject *sip_module;
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PyObject *sip_module_dict;
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PyObject *c_api;
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/* Import the SIP module. */
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sip_module = PyImport_ImportModule("sip");
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if (sip_module == NULL)
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return NULL;
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/* Get the module's dictionary. */
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sip_module_dict = PyModule_GetDict(sip_module);
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/* Get the "_C_API" attribute. */
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c_api = PyDict_GetItemString(sip_module_dict, "_C_API");
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if (c_api == NULL)
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return NULL;
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/* Sanity check that it is the right type. */
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if (!PyCObject_Check(c_api))
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return NULL;
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/* Get the actual pointer from the object. */
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return (const sipAPIDef *)PyCObject_AsVoidPtr(c_api);
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}
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