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Add PyLong Import/Export API (#121) · python/pythoncapi-compat@61709bf · GitHub

/ pythoncapi-compat Public

Commit 61709bf

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skirpichev
and
vstinner
authored
Add PyLong Import/Export API (#121)
PyPy is not supported, as well as Python 2. In the later case it's possible, but hardly worth code complications: most real-word potential consumers (e.g. Sage, gmpy2 or python-flint) support only Python 3. Co-authored-by: Victor Stinner <vstinner@python.org>
1 parent 900c130 commit 61709bf

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‎docs/api.rst‎

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@@ -29,6 +29,42 @@ Latest version of the header file:
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Python 3.14
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-----------
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.. c:struct:: PyLongLayout
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See `PyLongLayout documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongLayout>`__.
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.. c:function:: const PyLongLayout* PyLong_GetNativeLayout(void)
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See `PyLong_GetNativeLayout() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLong_GetNativeLayout>`__.
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.. c:struct:: PyLongExport
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See `PyLongExport documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongExport>`__.
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.. c:function:: int PyLong_Export(PyObject *obj, PyLongExport *export_long)
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See `PyLong_Export() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLong_Export>`__.
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.. c:function:: void PyLong_FreeExport(PyLongExport *export_long)
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See `PyLong_FreeExport() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLong_FreeExport>`__.
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.. c:struct:: PyLongWriter
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See `PyLongWriter documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongWriter>`__.
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.. c:function:: PyLongWriter* PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)
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See `PyLongWriter_Create() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongWriter_Create>`__.
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.. c:function:: PyObject* PyLongWriter_Finish(PyLongWriter *writer)
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See `PyLongWriter_Finish() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongWriter_Finish>`__.
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.. c:function:: void PyLongWriter_Discard(PyLongWriter *writer)
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See `PyLongWriter_Discard() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLongWriter_Discard>`__.
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.. c:function:: int PyLong_IsPositive(PyObject *obj)
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See `PyLong_IsPositive() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLong_IsPositive>`__.

‎docs/changelog.rst‎

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Changelog
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=========
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* 2024-12-13: Add functions and structs:
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* ``PyLongLayout``
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* ``PyLong_GetNativeLayout()``
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* ``PyLongExport``
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* ``PyLong_Export()``
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* ``PyLong_FreeExport()``
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* ``PyLongWriter``
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* ``PyLongWriter_Create()``
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* ``PyLongWriter_Finish()``
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* ``PyLongWriter_Discard()``
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* 2024-11-12: Add functions:
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* ``PyLong_IsPositive()``

‎pythoncapi_compat.h‎

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@@ -1720,6 +1720,185 @@ static inline int PyLong_AsUInt64(PyObject *obj, uint64_t *pvalue)
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#endif
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// gh-102471 added import and export API for integers to 3.14.0a2.
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#if PY_VERSION_HEX < 0x030E00A2 && PY_VERSION_HEX >= 0x03000000 && !defined(PYPY_VERSION)
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// Helpers to access PyLongObject internals.
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static inline void
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_PyLong_SetSignAndDigitCount(PyLongObject *op, int sign, Py_ssize_t size)
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{
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#if PY_VERSION_HEX >= 0x030C0000
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op->long_value.lv_tag = (uintptr_t)(1 - sign) | ((uintptr_t)(size) << 3);
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#elif PY_VERSION_HEX >= 0x030900A4
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Py_SET_SIZE(op, sign * size);
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#else
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Py_SIZE(op) = sign * size;
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#endif
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}
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static inline Py_ssize_t
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_PyLong_DigitCount(const PyLongObject *op)
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{
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#if PY_VERSION_HEX >= 0x030C0000
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return (Py_ssize_t)(op->long_value.lv_tag >> 3);
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#else
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return _PyLong_Sign((PyObject*)op) < 0 ? -Py_SIZE(op) : Py_SIZE(op);
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#endif
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}
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static inline digit*
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_PyLong_GetDigits(const PyLongObject *op)
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{
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#if PY_VERSION_HEX >= 0x030C0000
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return (digit*)(op->long_value.ob_digit);
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#else
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return (digit*)(op->ob_digit);
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#endif
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}
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typedef struct PyLongLayout {
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uint8_t bits_per_digit;
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uint8_t digit_size;
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int8_t digits_order;
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int8_t digit_endianness;
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} PyLongLayout;
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typedef struct PyLongExport {
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int64_t value;
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uint8_t negative;
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Py_ssize_t ndigits;
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const void *digits;
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Py_uintptr_t _reserved;
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} PyLongExport;
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typedef struct PyLongWriter PyLongWriter;
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static inline const PyLongLayout*
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PyLong_GetNativeLayout(void)
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{
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static const PyLongLayout PyLong_LAYOUT = {
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PyLong_SHIFT,
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sizeof(digit),
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-1, // least significant first
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PY_LITTLE_ENDIAN ? -1 : 1,
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};
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return &PyLong_LAYOUT;
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}
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static inline int
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PyLong_Export(PyObject *obj, PyLongExport *export_long)
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{
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if (!PyLong_Check(obj)) {
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memset(export_long, 0, sizeof(*export_long));
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PyErr_Format(PyExc_TypeError, "expected int, got %s",
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Py_TYPE(obj)->tp_name);
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return -1;
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}
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// Fast-path: try to convert to a int64_t
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PyLongObject *self = (PyLongObject*)obj;
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int overflow;
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#if SIZEOF_LONG == 8
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long value = PyLong_AsLongAndOverflow(obj, &overflow);
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#else
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// Windows has 32-bit long, so use 64-bit long long instead
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long long value = PyLong_AsLongLongAndOverflow(obj, &overflow);
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#endif
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Py_BUILD_ASSERT(sizeof(value) == sizeof(int64_t));
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// the function cannot fail since obj is a PyLongObject
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assert(!(value == -1 && PyErr_Occurred()));
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if (!overflow) {
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export_long->value = value;
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export_long->negative = 0;
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export_long->ndigits = 0;
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export_long->digits = 0;
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export_long->_reserved = 0;
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}
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else {
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export_long->value = 0;
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export_long->negative = _PyLong_Sign(obj) < 0;
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export_long->ndigits = _PyLong_DigitCount(self);
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if (export_long->ndigits == 0) {
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export_long->ndigits = 1;
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}
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export_long->digits = _PyLong_GetDigits(self);
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export_long->_reserved = (Py_uintptr_t)Py_NewRef(obj);
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}
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return 0;
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}
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static inline void
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PyLong_FreeExport(PyLongExport *export_long)
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{
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PyObject *obj = (PyObject*)export_long->_reserved;
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if (obj) {
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export_long->_reserved = 0;
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Py_DECREF(obj);
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}
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}
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static inline PyLongWriter*
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PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)
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{
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if (ndigits <= 0) {
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PyErr_SetString(PyExc_ValueError, "ndigits must be positive");
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return NULL;
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}
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assert(digits != NULL);
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PyLongObject *obj = _PyLong_New(ndigits);
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if (obj == NULL) {
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return NULL;
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}
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_PyLong_SetSignAndDigitCount(obj, negative?-1:1, ndigits);
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*digits = _PyLong_GetDigits(obj);
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return (PyLongWriter*)obj;
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}
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static inline void
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PyLongWriter_Discard(PyLongWriter *writer)
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{
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PyLongObject *obj = (PyLongObject *)writer;
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assert(Py_REFCNT(obj) == 1);
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Py_DECREF(obj);
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}
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static inline PyObject*
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PyLongWriter_Finish(PyLongWriter *writer)
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{
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PyObject *obj = (PyObject *)writer;
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PyLongObject *self = (PyLongObject*)obj;
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Py_ssize_t j = _PyLong_DigitCount(self);
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Py_ssize_t i = j;
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int sign = _PyLong_Sign(obj);
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assert(Py_REFCNT(obj) == 1);
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// Normalize and get singleton if possible
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while (i > 0 && _PyLong_GetDigits(self)[i-1] == 0) {
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--i;
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}
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if (i != j) {
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if (i == 0) {
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sign = 0;
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}
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_PyLong_SetSignAndDigitCount(self, sign, i);
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}
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if (i <= 1) {
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long val = sign * (long)(_PyLong_GetDigits(self)[0]);
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Py_DECREF(obj);
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return PyLong_FromLong(val);
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}
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return obj;
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}
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#endif
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#ifdef __cplusplus
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}
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#endif

‎tests/test_pythoncapi_compat_cext.c‎

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assert(PyLong_IsNegative(obj) == 0);
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assert(PyLong_IsZero(obj) == 0);
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#if defined(PYTHON3) && !defined(PYPY_VERSION)
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// test import/export API
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digit *digits;
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PyLongWriter *writer;
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static PyLongExport long_export;
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writer = PyLongWriter_Create(1, 1, (void**)&digits);
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PyLongWriter_Discard(writer);
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writer = PyLongWriter_Create(1, 1, (void**)&digits);
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digits[0] = 123;
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obj = PyLongWriter_Finish(writer);
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check_int(obj, -123);
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PyLong_Export(obj, &long_export);
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assert(long_export.value == -123);
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assert(long_export.digits == NULL);
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PyLong_FreeExport(&long_export);
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Py_DECREF(obj);
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writer = PyLongWriter_Create(0, 5, (void**)&digits);
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digits[0] = 1;
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digits[1] = 0;
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digits[2] = 0;
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digits[3] = 0;
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digits[4] = 1;
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obj = PyLongWriter_Finish(writer);
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PyLong_Export(obj, &long_export);
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assert(long_export.value == 0);
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digits = (digit*)long_export.digits;
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assert(digits[0] == 1);
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assert(digits[1] == 0);
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assert(digits[2] == 0);
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assert(digits[3] == 0);
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assert(digits[4] == 1);
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PyLong_FreeExport(&long_export);
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Py_DECREF(obj);
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const PyLongLayout *layout = PyLong_GetNativeLayout();
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assert(layout->digits_order == -1);
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assert(layout->digit_size == sizeof(digit));
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#endif // defined(PYTHON3) && !defined(PYPY_VERSION)
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Py_RETURN_NONE;
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}
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