671 lines
19 KiB
C
671 lines
19 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 "pycore_abstract.h" // _PyIndex_Check()
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#include "pycore_object.h" // _PyObject_GC_TRACK()
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#include "structmember.h" // PyMemberDef
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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_GET_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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static PyObject *
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ellipsis_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))
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{
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return PyUnicode_FromString("Ellipsis");
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}
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static PyMethodDef ellipsis_methods[] = {
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{"__reduce__", ellipsis_reduce, METH_NOARGS, NULL},
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{NULL, NULL}
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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_vectorcall_offset */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_as_async */
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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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ellipsis_methods, /* 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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void _PySlice_Fini(PyThreadState *tstate)
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{
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PyInterpreterState *interp = tstate->interp;
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PySliceObject *obj = interp->slice_cache;
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if (obj != NULL) {
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interp->slice_cache = NULL;
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PyObject_GC_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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if (step == NULL) {
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step = Py_None;
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}
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if (start == NULL) {
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start = Py_None;
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}
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if (stop == NULL) {
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stop = Py_None;
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}
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PyInterpreterState *interp = _PyInterpreterState_GET();
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PySliceObject *obj;
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if (interp->slice_cache != NULL) {
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obj = interp->slice_cache;
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interp->slice_cache = NULL;
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_Py_NewReference((PyObject *)obj);
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}
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else {
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obj = PyObject_GC_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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}
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Py_INCREF(step);
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obj->step = step;
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Py_INCREF(start);
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obj->start = start;
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Py_INCREF(stop);
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obj->stop = stop;
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_PyObject_GC_TRACK(obj);
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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_Unpack(PyObject *_r,
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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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/* this is harder to get right than you might think */
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Py_BUILD_ASSERT(PY_SSIZE_T_MIN + 1 <= -PY_SSIZE_T_MAX);
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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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if (r->start == Py_None) {
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*start = *step < 0 ? PY_SSIZE_T_MAX : 0;
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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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}
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if (r->stop == Py_None) {
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*stop = *step < 0 ? PY_SSIZE_T_MIN : PY_SSIZE_T_MAX;
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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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}
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return 0;
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}
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Py_ssize_t
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PySlice_AdjustIndices(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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/* this is harder to get right than you might think */
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assert(step != 0);
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assert(step >= -PY_SSIZE_T_MAX);
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if (*start < 0) {
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*start += length;
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if (*start < 0) {
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*start = (step < 0) ? -1 : 0;
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}
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}
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else if (*start >= length) {
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*start = (step < 0) ? length - 1 : length;
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}
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if (*stop < 0) {
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*stop += length;
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if (*stop < 0) {
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*stop = (step < 0) ? -1 : 0;
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}
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}
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else if (*stop >= length) {
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*stop = (step < 0) ? length - 1 : length;
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}
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if (step < 0) {
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if (*stop < *start) {
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return (*start - *stop - 1) / (-step) + 1;
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}
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}
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else {
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if (*start < *stop) {
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return (*stop - *start - 1) / step + 1;
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}
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}
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return 0;
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}
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#undef PySlice_GetIndicesEx
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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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if (PySlice_Unpack(_r, start, stop, step) < 0)
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return -1;
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*slicelength = PySlice_AdjustIndices(length, start, stop, *step);
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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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PyInterpreterState *interp = _PyInterpreterState_GET();
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_PyObject_GC_UNTRACK(r);
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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 (interp->slice_cache == NULL) {
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interp->slice_cache = r;
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}
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else {
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PyObject_GC_Del(r);
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}
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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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/* Helper function to convert a slice argument to a PyLong, and raise TypeError
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with a suitable message on failure. */
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static PyObject*
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evaluate_slice_index(PyObject *v)
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{
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if (_PyIndex_Check(v)) {
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return PyNumber_Index(v);
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}
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else {
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PyErr_SetString(PyExc_TypeError,
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"slice indices must be integers or "
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"None or have an __index__ method");
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return NULL;
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}
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}
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/* Compute slice indices given a slice and length. Return -1 on failure. Used
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by slice.indices and rangeobject slicing. Assumes that `len` is a
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nonnegative instance of PyLong. */
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int
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_PySlice_GetLongIndices(PySliceObject *self, PyObject *length,
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PyObject **start_ptr, PyObject **stop_ptr,
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PyObject **step_ptr)
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{
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PyObject *start=NULL, *stop=NULL, *step=NULL;
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PyObject *upper=NULL, *lower=NULL;
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int step_is_negative, cmp_result;
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/* Convert step to an integer; raise for zero step. */
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if (self->step == Py_None) {
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step = _PyLong_One;
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Py_INCREF(step);
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step_is_negative = 0;
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}
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else {
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int step_sign;
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step = evaluate_slice_index(self->step);
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if (step == NULL)
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goto error;
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step_sign = _PyLong_Sign(step);
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if (step_sign == 0) {
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PyErr_SetString(PyExc_ValueError,
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"slice step cannot be zero");
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goto error;
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}
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step_is_negative = step_sign < 0;
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}
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/* Find lower and upper bounds for start and stop. */
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if (step_is_negative) {
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lower = PyLong_FromLong(-1L);
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if (lower == NULL)
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goto error;
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upper = PyNumber_Add(length, lower);
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if (upper == NULL)
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goto error;
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}
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else {
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lower = _PyLong_Zero;
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Py_INCREF(lower);
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upper = length;
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Py_INCREF(upper);
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}
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/* Compute start. */
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if (self->start == Py_None) {
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start = step_is_negative ? upper : lower;
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Py_INCREF(start);
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}
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else {
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start = evaluate_slice_index(self->start);
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if (start == NULL)
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goto error;
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if (_PyLong_Sign(start) < 0) {
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/* start += length */
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PyObject *tmp = PyNumber_Add(start, length);
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Py_DECREF(start);
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start = tmp;
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if (start == NULL)
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goto error;
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cmp_result = PyObject_RichCompareBool(start, lower, Py_LT);
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if (cmp_result < 0)
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goto error;
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if (cmp_result) {
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Py_INCREF(lower);
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Py_DECREF(start);
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start = lower;
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}
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}
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else {
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cmp_result = PyObject_RichCompareBool(start, upper, Py_GT);
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if (cmp_result < 0)
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goto error;
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if (cmp_result) {
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Py_INCREF(upper);
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Py_DECREF(start);
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start = upper;
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}
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}
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}
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/* Compute stop. */
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if (self->stop == Py_None) {
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stop = step_is_negative ? lower : upper;
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Py_INCREF(stop);
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}
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else {
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stop = evaluate_slice_index(self->stop);
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if (stop == NULL)
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goto error;
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if (_PyLong_Sign(stop) < 0) {
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/* stop += length */
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PyObject *tmp = PyNumber_Add(stop, length);
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Py_DECREF(stop);
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stop = tmp;
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if (stop == NULL)
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goto error;
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cmp_result = PyObject_RichCompareBool(stop, lower, Py_LT);
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if (cmp_result < 0)
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goto error;
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if (cmp_result) {
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Py_INCREF(lower);
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Py_DECREF(stop);
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stop = lower;
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}
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}
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else {
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cmp_result = PyObject_RichCompareBool(stop, upper, Py_GT);
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if (cmp_result < 0)
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goto error;
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if (cmp_result) {
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Py_INCREF(upper);
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Py_DECREF(stop);
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stop = upper;
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}
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}
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}
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*start_ptr = start;
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*stop_ptr = stop;
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*step_ptr = step;
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Py_DECREF(upper);
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Py_DECREF(lower);
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return 0;
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error:
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*start_ptr = *stop_ptr = *step_ptr = NULL;
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Py_XDECREF(start);
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Py_XDECREF(stop);
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Py_XDECREF(step);
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Py_XDECREF(upper);
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Py_XDECREF(lower);
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return -1;
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}
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/* Implementation of slice.indices. */
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static PyObject*
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slice_indices(PySliceObject* self, PyObject* len)
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{
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PyObject *start, *stop, *step;
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PyObject *length;
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int error;
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/* Convert length to an integer if necessary; raise for negative length. */
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length = PyNumber_Index(len);
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if (length == NULL)
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return NULL;
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|
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if (_PyLong_Sign(length) < 0) {
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PyErr_SetString(PyExc_ValueError,
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"length should not be negative");
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Py_DECREF(length);
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return NULL;
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}
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|
error = _PySlice_GetLongIndices(self, length, &start, &stop, &step);
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Py_DECREF(length);
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|
if (error == -1)
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return NULL;
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|
else
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return Py_BuildValue("(NNN)", start, stop, step);
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}
|
|
|
|
PyDoc_STRVAR(slice_indices_doc,
|
|
"S.indices(len) -> (start, stop, stride)\n\
|
|
\n\
|
|
Assuming a sequence of length len, calculate the start and stop\n\
|
|
indices, and the stride length of the extended slice described by\n\
|
|
S. Out of bounds indices are clipped in a manner consistent with the\n\
|
|
handling of normal slices.");
|
|
|
|
static PyObject *
|
|
slice_reduce(PySliceObject* self, PyObject *Py_UNUSED(ignored))
|
|
{
|
|
return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
|
|
}
|
|
|
|
PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
|
|
|
|
static PyMethodDef slice_methods[] = {
|
|
{"indices", (PyCFunction)slice_indices,
|
|
METH_O, slice_indices_doc},
|
|
{"__reduce__", (PyCFunction)slice_reduce,
|
|
METH_NOARGS, reduce_doc},
|
|
{NULL, NULL}
|
|
};
|
|
|
|
static PyObject *
|
|
slice_richcompare(PyObject *v, PyObject *w, int op)
|
|
{
|
|
if (!PySlice_Check(v) || !PySlice_Check(w))
|
|
Py_RETURN_NOTIMPLEMENTED;
|
|
|
|
if (v == w) {
|
|
PyObject *res;
|
|
/* XXX Do we really need this shortcut?
|
|
There's a unit test for it, but is that fair? */
|
|
switch (op) {
|
|
case Py_EQ:
|
|
case Py_LE:
|
|
case Py_GE:
|
|
res = Py_True;
|
|
break;
|
|
default:
|
|
res = Py_False;
|
|
break;
|
|
}
|
|
Py_INCREF(res);
|
|
return res;
|
|
}
|
|
|
|
|
|
PyObject *t1 = PyTuple_Pack(3,
|
|
((PySliceObject *)v)->start,
|
|
((PySliceObject *)v)->stop,
|
|
((PySliceObject *)v)->step);
|
|
if (t1 == NULL) {
|
|
return NULL;
|
|
}
|
|
|
|
PyObject *t2 = PyTuple_Pack(3,
|
|
((PySliceObject *)w)->start,
|
|
((PySliceObject *)w)->stop,
|
|
((PySliceObject *)w)->step);
|
|
if (t2 == NULL) {
|
|
Py_DECREF(t1);
|
|
return NULL;
|
|
}
|
|
|
|
PyObject *res = PyObject_RichCompare(t1, t2, op);
|
|
Py_DECREF(t1);
|
|
Py_DECREF(t2);
|
|
return res;
|
|
}
|
|
|
|
static int
|
|
slice_traverse(PySliceObject *v, visitproc visit, void *arg)
|
|
{
|
|
Py_VISIT(v->start);
|
|
Py_VISIT(v->stop);
|
|
Py_VISIT(v->step);
|
|
return 0;
|
|
}
|
|
|
|
PyTypeObject PySlice_Type = {
|
|
PyVarObject_HEAD_INIT(&PyType_Type, 0)
|
|
"slice", /* Name of this type */
|
|
sizeof(PySliceObject), /* Basic object size */
|
|
0, /* Item size for varobject */
|
|
(destructor)slice_dealloc, /* tp_dealloc */
|
|
0, /* tp_vectorcall_offset */
|
|
0, /* tp_getattr */
|
|
0, /* tp_setattr */
|
|
0, /* tp_as_async */
|
|
(reprfunc)slice_repr, /* tp_repr */
|
|
0, /* tp_as_number */
|
|
0, /* tp_as_sequence */
|
|
0, /* tp_as_mapping */
|
|
PyObject_HashNotImplemented, /* tp_hash */
|
|
0, /* tp_call */
|
|
0, /* tp_str */
|
|
PyObject_GenericGetAttr, /* tp_getattro */
|
|
0, /* tp_setattro */
|
|
0, /* tp_as_buffer */
|
|
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
|
|
slice_doc, /* tp_doc */
|
|
(traverseproc)slice_traverse, /* tp_traverse */
|
|
0, /* tp_clear */
|
|
slice_richcompare, /* tp_richcompare */
|
|
0, /* tp_weaklistoffset */
|
|
0, /* tp_iter */
|
|
0, /* tp_iternext */
|
|
slice_methods, /* tp_methods */
|
|
slice_members, /* tp_members */
|
|
0, /* tp_getset */
|
|
0, /* tp_base */
|
|
0, /* tp_dict */
|
|
0, /* tp_descr_get */
|
|
0, /* tp_descr_set */
|
|
0, /* tp_dictoffset */
|
|
0, /* tp_init */
|
|
0, /* tp_alloc */
|
|
slice_new, /* tp_new */
|
|
};
|