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// Copyright (C) 2024 Stewart Miles
// Licensed to the Python Software Foundation under a contributor agreement.
// See LICENSE.txt and CONTRIBUTORS.txt.
// Use the limited API to ensure ABI compatibility across all major Python
// versions starting from 3.2
// https://docs.python.org/3/c-api/stable.html#limited-c-api
#if !defined(Py_LIMITED_API)
#define Py_LIMITED_API 3
#endif // !defined(Py_LIMITED_API)
#define PY_SSIZE_T_CLEAN
#include <Python.h>
// Name and doc string for this module.
#define MODULE_NAME calculate
#define MODULE_DOCS "Calculates Fibonacci numbers."
// Convert the argument into a string.
#define _STRINGIFY(x) #x
#define STRINGIFY(x) _STRINGIFY(x)
// Calculate a Fibonacci number at the specified index of the sequence.
static PyObject *fib(PyObject *self, PyObject *args)
{
long int index;
if (!PyArg_ParseTuple(args, "l", &index)) {
PyErr_SetString(PyExc_ValueError, "An index must be specified.");
}
long int current_value = 1;
long int previous_value = 0;
index--;
for ( ; index > 0 ; --index) {
long int next_value = current_value + previous_value;
previous_value = current_value;
current_value = next_value;
}
return PyLong_FromLong(current_value);
}
// Exposes methods in this module.
static PyMethodDef methods[] =
{
{
"fib",
fib,
METH_VARARGS,
PyDoc_STR("Calculate a Fibonacci number.\n"
"\n"
":param index: Index of the number in the Fibonacci sequence\n"
" to calculate.\n"
"\n"
":returns: Fibonacci number at the specified index.\n"
" For example an index of 7 will return 13\n"),
},
};
#if PY_MAJOR_VERSION >= 3
// Defines the module.
static struct PyModuleDef module =
{
PyModuleDef_HEAD_INIT,
STRINGIFY(MODULE_NAME),
PyDoc_STR(MODULE_DOCS),
-1,
methods,
};
#endif // PY_MAJOR_VERSION >= 3
// Expands to the init function name.
#define _PYINIT_FUNCTION_NAME(prefix, name) prefix ## name
#define PYINIT_FUNCTION_NAME(prefix, name) _PYINIT_FUNCTION_NAME(prefix, name)
// Initialize this module.
#if PY_MAJOR_VERSION >= 3
PyMODINIT_FUNC
PYINIT_FUNCTION_NAME(PyInit_, MODULE_NAME)(void)
{
return PyModule_Create(&module);
}
#else
PyMODINIT_FUNC
PYINIT_FUNCTION_NAME(init, MODULE_NAME)(void)
{
// Ignore the returned module object.
(void)Py_InitModule(STRINGIFY(MODULE_NAME), methods);
}
#endif // PY_MAJOR_VERSION >= 3
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