cpython/Modules/xxlimited.c

/* Use this file as a template to start implementing a module that
   also declares object types. All occurrences of 'Xxo' should be changed
   to something reasonable for your objects. After that, all other
   occurrences of 'xx' should be changed to something reasonable for your
   module. If your module is named foo your source file should be named
   foo.c or foomodule.c.

   You will probably want to delete all references to 'x_attr' and add
   your own types of attributes instead.  Maybe you want to name your
   local variables other than 'self'.  If your object type is needed in
   other files, you'll have to create a file "foobarobject.h"; see
   floatobject.h for an example.

   This module roughly corresponds to::

      class Xxo:
         """A class that explicitly stores attributes in an internal dict"""

          def __init__(self):
              # In the C class, "_x_attr" is not accessible from Python code
              self._x_attr = {}
              self._x_exports = 0

          def __getattr__(self, name):
              return self._x_attr[name]

          def __setattr__(self, name, value):
              self._x_attr[name] = value

          def __delattr__(self, name):
              del self._x_attr[name]

          @property
          def x_exports(self):
              """Return the number of times an internal buffer is exported."""
              # Each Xxo instance has a 10-byte buffer that can be
              # accessed via the buffer interface (e.g. `memoryview`).
              return self._x_exports

          def demo(o, /):
              if isinstance(o, str):
                  return o
              elif isinstance(o, Xxo):
                  return o
              else:
                  raise Error('argument must be str or Xxo')

      class Error(Exception):
          """Exception raised by the xxlimited module"""

      def foo(i: int, j: int, /):
          """Return the sum of i and j."""
          # Unlike this pseudocode, the C function will *only* work with
          # integers and perform C long int arithmetic
          return i + j

      def new():
          return Xxo()

      def Str(str):
          # A trivial subclass of a built-in type
          pass
   */

// Need limited C API version 3.13 for Py_mod_gil
#include "pyconfig.h"   // Py_GIL_DISABLED
#ifndef Py_GIL_DISABLED
#define Py_LIMITED_API …
#endif

#include "Python.h"
#include <string.h>

#define BUFSIZE …

// Module state
xx_state;


/* Xxo objects */

// Instance state
XxoObject;

// XXX: no good way to do this yet
// #define XxoObject_Check(v)      Py_IS_TYPE(v, Xxo_Type)

static XxoObject *
newXxoObject(PyObject *module)
{ … }

/* Xxo finalization */

static int
Xxo_traverse(PyObject *self_obj, visitproc visit, void *arg)
{ … }

static int
Xxo_clear(XxoObject *self)
{ … }

static void
Xxo_finalize(PyObject *self_obj)
{ … }

static void
Xxo_dealloc(PyObject *self)
{ … }


/* Xxo attribute handling */

static PyObject *
Xxo_getattro(XxoObject *self, PyObject *name)
{ … }

static int
Xxo_setattro(XxoObject *self, PyObject *name, PyObject *v)
{ … }

/* Xxo methods */

static PyObject *
Xxo_demo(XxoObject *self, PyTypeObject *defining_class,
         PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
{ … }

static PyMethodDef Xxo_methods[] = …;

/* Xxo buffer interface */

static int
Xxo_getbuffer(XxoObject *self, Py_buffer *view, int flags)
{ … }

static void
Xxo_releasebuffer(XxoObject *self, Py_buffer *view)
{ … }

static PyObject *
Xxo_get_x_exports(XxoObject *self, void *c)
{ … }

/* Xxo type definition */

PyDoc_STRVAR(Xxo_doc,
             "A class that explicitly stores attributes in an internal dict");

static PyGetSetDef Xxo_getsetlist[] = …;


static PyType_Slot Xxo_Type_slots[] = …;

static PyType_Spec Xxo_Type_spec = …;


/* Str type definition*/

static PyType_Slot Str_Type_slots[] = …;

static PyType_Spec Str_Type_spec = …;


/* Function of two integers returning integer (with C "long int" arithmetic) */

PyDoc_STRVAR(xx_foo_doc,
"foo(i,j)\n\
\n\
Return the sum of i and j.");

static PyObject *
xx_foo(PyObject *module, PyObject *args)
{ … }


/* Function of no arguments returning new Xxo object */

static PyObject *
xx_new(PyObject *module, PyObject *Py_UNUSED(unused))
{ … }



/* List of functions defined in the module */

static PyMethodDef xx_methods[] = …;


/* The module itself */

PyDoc_STRVAR(module_doc,
"This is a template module just for instruction.");

static int
xx_modexec(PyObject *m)
{ … }

static PyModuleDef_Slot xx_slots[] = …;

static int
xx_traverse(PyObject *module, visitproc visit, void *arg)
{ … }

static int
xx_clear(PyObject *module)
{ … }

static struct PyModuleDef xxmodule = …;


/* Export function for the module (*must* be called PyInit_xx) */

PyMODINIT_FUNC
PyInit_xxlimited(void)
{ … }