mirror of https://github.com/python/cpython.git
443 lines
14 KiB
C
443 lines
14 KiB
C
/*
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Written by Jim Hugunin and Chris Chase.
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This includes both the singular ellipsis object and slice objects.
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Guido, feel free to do whatever you want in the way of copyrights
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for this file.
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*/
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/*
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Py_Ellipsis encodes the '...' rubber index token. It is similar to
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the Py_NoneStruct in that there is no way to create other objects of
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this type and there is exactly one in existence.
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*/
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#include "Python.h"
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#include "structmember.h"
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static PyObject *
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ellipsis_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
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{
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if (PyTuple_GET_SIZE(args) || (kwargs && PyDict_Size(kwargs))) {
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PyErr_SetString(PyExc_TypeError, "EllipsisType takes no arguments");
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return NULL;
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}
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Py_INCREF(Py_Ellipsis);
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return Py_Ellipsis;
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}
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static PyObject *
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ellipsis_repr(PyObject *op)
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{
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return PyUnicode_FromString("Ellipsis");
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}
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PyTypeObject PyEllipsis_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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"ellipsis", /* tp_name */
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0, /* tp_basicsize */
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0, /* tp_itemsize */
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0, /*never called*/ /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_reserved */
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ellipsis_repr, /* tp_repr */
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0, /* tp_as_number */
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0, /* tp_as_sequence */
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0, /* tp_as_mapping */
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0, /* tp_hash */
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0, /* tp_call */
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0, /* tp_str */
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT, /* tp_flags */
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0, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
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0, /* tp_richcompare */
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0, /* tp_weaklistoffset */
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0, /* tp_iter */
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0, /* tp_iternext */
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0, /* tp_methods */
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0, /* tp_members */
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0, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0, /* tp_alloc */
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ellipsis_new, /* tp_new */
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};
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PyObject _Py_EllipsisObject = {
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_PyObject_EXTRA_INIT
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1, &PyEllipsis_Type
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};
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/* Slice object implementation */
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/* Using a cache is very effective since typically only a single slice is
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* created and then deleted again
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*/
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static PySliceObject *slice_cache = NULL;
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void PySlice_Fini(void)
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{
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PySliceObject *obj = slice_cache;
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if (obj != NULL) {
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slice_cache = NULL;
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PyObject_Del(obj);
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}
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}
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/* start, stop, and step are python objects with None indicating no
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index is present.
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*/
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PyObject *
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PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
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{
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PySliceObject *obj;
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if (slice_cache != NULL) {
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obj = slice_cache;
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slice_cache = NULL;
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_Py_NewReference((PyObject *)obj);
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} else {
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obj = PyObject_New(PySliceObject, &PySlice_Type);
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if (obj == NULL)
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return NULL;
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}
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if (step == NULL) step = Py_None;
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Py_INCREF(step);
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if (start == NULL) start = Py_None;
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Py_INCREF(start);
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if (stop == NULL) stop = Py_None;
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Py_INCREF(stop);
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obj->step = step;
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obj->start = start;
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obj->stop = stop;
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return (PyObject *) obj;
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}
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PyObject *
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_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
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{
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PyObject *start, *end, *slice;
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start = PyLong_FromSsize_t(istart);
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if (!start)
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return NULL;
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end = PyLong_FromSsize_t(istop);
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if (!end) {
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Py_DECREF(start);
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return NULL;
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}
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slice = PySlice_New(start, end, NULL);
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Py_DECREF(start);
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Py_DECREF(end);
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return slice;
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}
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int
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PySlice_GetIndices(PyObject *_r, Py_ssize_t length,
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Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
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{
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PySliceObject *r = (PySliceObject*)_r;
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/* XXX support long ints */
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if (r->step == Py_None) {
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*step = 1;
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} else {
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if (!PyLong_Check(r->step)) return -1;
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*step = PyLong_AsSsize_t(r->step);
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}
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if (r->start == Py_None) {
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*start = *step < 0 ? length-1 : 0;
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} else {
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if (!PyLong_Check(r->start)) return -1;
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*start = PyLong_AsSsize_t(r->start);
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if (*start < 0) *start += length;
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}
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if (r->stop == Py_None) {
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*stop = *step < 0 ? -1 : length;
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} else {
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if (!PyLong_Check(r->stop)) return -1;
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*stop = PyLong_AsSsize_t(r->stop);
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if (*stop < 0) *stop += length;
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}
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if (*stop > length) return -1;
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if (*start >= length) return -1;
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if (*step == 0) return -1;
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return 0;
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}
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int
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PySlice_GetIndicesEx(PyObject *_r, Py_ssize_t length,
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Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step,
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Py_ssize_t *slicelength)
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{
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PySliceObject *r = (PySliceObject*)_r;
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/* this is harder to get right than you might think */
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Py_ssize_t defstart, defstop;
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if (r->step == Py_None) {
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*step = 1;
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}
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else {
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if (!_PyEval_SliceIndex(r->step, step)) return -1;
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if (*step == 0) {
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PyErr_SetString(PyExc_ValueError,
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"slice step cannot be zero");
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return -1;
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}
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/* Here *step might be -PY_SSIZE_T_MAX-1; in this case we replace it
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* with -PY_SSIZE_T_MAX. This doesn't affect the semantics, and it
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* guards against later undefined behaviour resulting from code that
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* does "step = -step" as part of a slice reversal.
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*/
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if (*step < -PY_SSIZE_T_MAX)
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*step = -PY_SSIZE_T_MAX;
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}
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defstart = *step < 0 ? length-1 : 0;
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defstop = *step < 0 ? -1 : length;
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if (r->start == Py_None) {
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*start = defstart;
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}
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else {
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if (!_PyEval_SliceIndex(r->start, start)) return -1;
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if (*start < 0) *start += length;
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if (*start < 0) *start = (*step < 0) ? -1 : 0;
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if (*start >= length)
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*start = (*step < 0) ? length - 1 : length;
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}
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if (r->stop == Py_None) {
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*stop = defstop;
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}
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else {
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if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
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if (*stop < 0) *stop += length;
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if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
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if (*stop >= length)
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*stop = (*step < 0) ? length - 1 : length;
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}
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if ((*step < 0 && *stop >= *start)
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|| (*step > 0 && *start >= *stop)) {
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*slicelength = 0;
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}
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else if (*step < 0) {
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*slicelength = (*stop-*start+1)/(*step)+1;
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}
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else {
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*slicelength = (*stop-*start-1)/(*step)+1;
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}
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return 0;
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}
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static PyObject *
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slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
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{
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PyObject *start, *stop, *step;
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start = stop = step = NULL;
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if (!_PyArg_NoKeywords("slice()", kw))
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return NULL;
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if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
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return NULL;
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/* This swapping of stop and start is to maintain similarity with
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range(). */
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if (stop == NULL) {
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stop = start;
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start = NULL;
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}
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return PySlice_New(start, stop, step);
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}
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PyDoc_STRVAR(slice_doc,
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"slice(stop)\n\
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slice(start, stop[, step])\n\
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\n\
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Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
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static void
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slice_dealloc(PySliceObject *r)
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{
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Py_DECREF(r->step);
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Py_DECREF(r->start);
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Py_DECREF(r->stop);
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if (slice_cache == NULL)
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slice_cache = r;
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else
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PyObject_Del(r);
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}
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static PyObject *
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slice_repr(PySliceObject *r)
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{
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return PyUnicode_FromFormat("slice(%R, %R, %R)", r->start, r->stop, r->step);
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}
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static PyMemberDef slice_members[] = {
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{"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
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{"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
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{"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
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{0}
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};
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static PyObject*
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slice_indices(PySliceObject* self, PyObject* len)
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{
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Py_ssize_t ilen, start, stop, step, slicelength;
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ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
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if (ilen == -1 && PyErr_Occurred()) {
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return NULL;
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}
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if (PySlice_GetIndicesEx((PyObject*)self, ilen, &start, &stop,
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&step, &slicelength) < 0) {
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return NULL;
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}
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return Py_BuildValue("(nnn)", start, stop, step);
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}
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PyDoc_STRVAR(slice_indices_doc,
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"S.indices(len) -> (start, stop, stride)\n\
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\n\
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Assuming a sequence of length len, calculate the start and stop\n\
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indices, and the stride length of the extended slice described by\n\
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S. Out of bounds indices are clipped in a manner consistent with the\n\
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handling of normal slices.");
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static PyObject *
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slice_reduce(PySliceObject* self)
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{
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return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
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}
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PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
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static PyMethodDef slice_methods[] = {
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{"indices", (PyCFunction)slice_indices,
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METH_O, slice_indices_doc},
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{"__reduce__", (PyCFunction)slice_reduce,
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METH_NOARGS, reduce_doc},
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{NULL, NULL}
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};
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static PyObject *
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slice_richcompare(PyObject *v, PyObject *w, int op)
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{
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PyObject *t1;
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PyObject *t2;
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PyObject *res;
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if (!PySlice_Check(v) || !PySlice_Check(w))
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Py_RETURN_NOTIMPLEMENTED;
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if (v == w) {
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/* XXX Do we really need this shortcut?
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There's a unit test for it, but is that fair? */
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switch (op) {
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case Py_EQ:
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case Py_LE:
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case Py_GE:
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res = Py_True;
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break;
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default:
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res = Py_False;
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break;
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}
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Py_INCREF(res);
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return res;
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}
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t1 = PyTuple_New(3);
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if (t1 == NULL)
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return NULL;
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t2 = PyTuple_New(3);
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if (t2 == NULL) {
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Py_DECREF(t1);
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return NULL;
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}
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PyTuple_SET_ITEM(t1, 0, ((PySliceObject *)v)->start);
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PyTuple_SET_ITEM(t1, 1, ((PySliceObject *)v)->stop);
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PyTuple_SET_ITEM(t1, 2, ((PySliceObject *)v)->step);
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PyTuple_SET_ITEM(t2, 0, ((PySliceObject *)w)->start);
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PyTuple_SET_ITEM(t2, 1, ((PySliceObject *)w)->stop);
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PyTuple_SET_ITEM(t2, 2, ((PySliceObject *)w)->step);
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res = PyObject_RichCompare(t1, t2, op);
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PyTuple_SET_ITEM(t1, 0, NULL);
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PyTuple_SET_ITEM(t1, 1, NULL);
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PyTuple_SET_ITEM(t1, 2, NULL);
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PyTuple_SET_ITEM(t2, 0, NULL);
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PyTuple_SET_ITEM(t2, 1, NULL);
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PyTuple_SET_ITEM(t2, 2, NULL);
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Py_DECREF(t1);
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Py_DECREF(t2);
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return res;
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}
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PyTypeObject PySlice_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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"slice", /* Name of this type */
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sizeof(PySliceObject), /* Basic object size */
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0, /* Item size for varobject */
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(destructor)slice_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_reserved */
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(reprfunc)slice_repr, /* tp_repr */
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0, /* tp_as_number */
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0, /* tp_as_sequence */
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0, /* tp_as_mapping */
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PyObject_HashNotImplemented, /* tp_hash */
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0, /* tp_call */
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0, /* tp_str */
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT, /* tp_flags */
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slice_doc, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
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slice_richcompare, /* tp_richcompare */
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0, /* tp_weaklistoffset */
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0, /* tp_iter */
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0, /* tp_iternext */
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slice_methods, /* tp_methods */
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slice_members, /* tp_members */
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0, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0, /* tp_alloc */
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slice_new, /* tp_new */
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};
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