/src/Python-3.8.3/Objects/sliceobject.c

Source
/*
Written by Jim Hugunin and Chris Chase.

This includes both the singular ellipsis object and slice objects.

Guido, feel free to do whatever you want in the way of copyrights
for this file.
*/

/*
Py_Ellipsis encodes the '...' rubber index token. It is similar to
the Py_NoneStruct in that there is no way to create other objects of
this type and there is exactly one in existence.
*/

#include "Python.h"
#include "pycore_object.h"
#include "pycore_pymem.h"
#include "pycore_pystate.h"
#include "structmember.h"

static PyObject *
ellipsis_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
{
    if (PyTuple_GET_SIZE(args) || (kwargs && PyDict_GET_SIZE(kwargs))) {
        PyErr_SetString(PyExc_TypeError, "EllipsisType takes no arguments");
        return NULL;
    }
    Py_INCREF(Py_Ellipsis);
    return Py_Ellipsis;
}

static PyObject *
ellipsis_repr(PyObject *op)
{
    return PyUnicode_FromString("Ellipsis");
}

static PyObject *
ellipsis_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))
{
    return PyUnicode_FromString("Ellipsis");
}

static PyMethodDef ellipsis_methods[] = {
    {"__reduce__", ellipsis_reduce, METH_NOARGS, NULL},
    {NULL, NULL}
};

PyTypeObject PyEllipsis_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "ellipsis",                         /* tp_name */
    0,                                  /* tp_basicsize */
    0,                                  /* tp_itemsize */
    0, /*never called*/                 /* tp_dealloc */
    0,                                  /* tp_vectorcall_offset */
    0,                                  /* tp_getattr */
    0,                                  /* tp_setattr */
    0,                                  /* tp_as_async */
    ellipsis_repr,                      /* tp_repr */
    0,                                  /* tp_as_number */
    0,                                  /* tp_as_sequence */
    0,                                  /* tp_as_mapping */
    0,                                  /* tp_hash */
    0,                                  /* tp_call */
    0,                                  /* tp_str */
    PyObject_GenericGetAttr,            /* tp_getattro */
    0,                                  /* tp_setattro */
    0,                                  /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT,                 /* tp_flags */
    0,                                  /* tp_doc */
    0,                                  /* tp_traverse */
    0,                                  /* tp_clear */
    0,                                  /* tp_richcompare */
    0,                                  /* tp_weaklistoffset */
    0,                                  /* tp_iter */
    0,                                  /* tp_iternext */
    ellipsis_methods,                   /* tp_methods */
    0,                                  /* 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 */
    ellipsis_new,                       /* tp_new */
};

PyObject _Py_EllipsisObject = {
    _PyObject_EXTRA_INIT
    1, &PyEllipsis_Type
};


/* Slice object implementation */

/* Using a cache is very effective since typically only a single slice is
 * created and then deleted again
 */
static PySliceObject *slice_cache = NULL;
void PySlice_Fini(void)
{
    PySliceObject *obj = slice_cache;
    if (obj != NULL) {
        slice_cache = NULL;
        PyObject_GC_Del(obj);
    }
}

/* start, stop, and step are python objects with None indicating no
   index is present.
*/

PyObject *
PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
{
    PySliceObject *obj;
    if (slice_cache != NULL) {
        obj = slice_cache;
        slice_cache = NULL;
        _Py_NewReference((PyObject *)obj);
    } else {
        obj = PyObject_GC_New(PySliceObject, &PySlice_Type);
        if (obj == NULL)
            return NULL;
    }

    if (step == NULL) step = Py_None;
    Py_INCREF(step);
    if (start == NULL) start = Py_None;
    Py_INCREF(start);
    if (stop == NULL) stop = Py_None;
    Py_INCREF(stop);

    obj->step = step;
    obj->start = start;
    obj->stop = stop;

    _PyObject_GC_TRACK(obj);
    return (PyObject *) obj;
}

PyObject *
_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
{
    PyObject *start, *end, *slice;
    start = PyLong_FromSsize_t(istart);
    if (!start)
        return NULL;
    end = PyLong_FromSsize_t(istop);
    if (!end) {
        Py_DECREF(start);
        return NULL;
    }

    slice = PySlice_New(start, end, NULL);
    Py_DECREF(start);
    Py_DECREF(end);
    return slice;
}

int
PySlice_GetIndices(PyObject *_r, Py_ssize_t length,
                   Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
{
    PySliceObject *r = (PySliceObject*)_r;
    /* XXX support long ints */
    if (r->step == Py_None) {
        *step = 1;
    } else {
        if (!PyLong_Check(r->step)) return -1;
        *step = PyLong_AsSsize_t(r->step);
    }
    if (r->start == Py_None) {
        *start = *step < 0 ? length-1 : 0;
    } else {
        if (!PyLong_Check(r->start)) return -1;
        *start = PyLong_AsSsize_t(r->start);
        if (*start < 0) *start += length;
    }
    if (r->stop == Py_None) {
        *stop = *step < 0 ? -1 : length;
    } else {
        if (!PyLong_Check(r->stop)) return -1;
        *stop = PyLong_AsSsize_t(r->stop);
        if (*stop < 0) *stop += length;
    }
    if (*stop > length) return -1;
    if (*start >= length) return -1;
    if (*step == 0) return -1;
    return 0;
}

int
PySlice_Unpack(PyObject *_r,
               Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
{
    PySliceObject *r = (PySliceObject*)_r;
    /* this is harder to get right than you might think */

    Py_BUILD_ASSERT(PY_SSIZE_T_MIN + 1 <= -PY_SSIZE_T_MAX);

    if (r->step == Py_None) {
        *step = 1;
    }
    else {
        if (!_PyEval_SliceIndex(r->step, step)) return -1;
        if (*step == 0) {
            PyErr_SetString(PyExc_ValueError,
                            "slice step cannot be zero");
            return -1;
        }
        /* Here *step might be -PY_SSIZE_T_MAX-1; in this case we replace it
         * with -PY_SSIZE_T_MAX.  This doesn't affect the semantics, and it
         * guards against later undefined behaviour resulting from code that
         * does "step = -step" as part of a slice reversal.
         */
        if (*step < -PY_SSIZE_T_MAX)
            *step = -PY_SSIZE_T_MAX;
    }

    if (r->start == Py_None) {
        *start = *step < 0 ? PY_SSIZE_T_MAX : 0;
    }
    else {
        if (!_PyEval_SliceIndex(r->start, start)) return -1;
    }

    if (r->stop == Py_None) {
        *stop = *step < 0 ? PY_SSIZE_T_MIN : PY_SSIZE_T_MAX;
    }
    else {
        if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
    }

    return 0;
}

Py_ssize_t
PySlice_AdjustIndices(Py_ssize_t length,
                      Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t step)
{
    /* this is harder to get right than you might think */

    assert(step != 0);
    assert(step >= -PY_SSIZE_T_MAX);

    if (*start < 0) {
        *start += length;
        if (*start < 0) {
            *start = (step < 0) ? -1 : 0;
        }
    }
    else if (*start >= length) {
        *start = (step < 0) ? length - 1 : length;
    }

    if (*stop < 0) {
        *stop += length;
        if (*stop < 0) {
            *stop = (step < 0) ? -1 : 0;
        }
    }
    else if (*stop >= length) {
        *stop = (step < 0) ? length - 1 : length;
    }

    if (step < 0) {
        if (*stop < *start) {
            return (*start - *stop - 1) / (-step) + 1;
        }
    }
    else {
        if (*start < *stop) {
            return (*stop - *start - 1) / step + 1;
        }
    }
    return 0;
}

#undef PySlice_GetIndicesEx

int
PySlice_GetIndicesEx(PyObject *_r, Py_ssize_t length,
                     Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step,
                     Py_ssize_t *slicelength)
{
    if (PySlice_Unpack(_r, start, stop, step) < 0)
        return -1;
    *slicelength = PySlice_AdjustIndices(length, start, stop, *step);
    return 0;
}

static PyObject *
slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
    PyObject *start, *stop, *step;

    start = stop = step = NULL;

    if (!_PyArg_NoKeywords("slice", kw))
        return NULL;

    if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
        return NULL;

    /* This swapping of stop and start is to maintain similarity with
       range(). */
    if (stop == NULL) {
        stop = start;
        start = NULL;
    }
    return PySlice_New(start, stop, step);
}

PyDoc_STRVAR(slice_doc,
"slice(stop)\n\
slice(start, stop[, step])\n\
\n\
Create a slice object.  This is used for extended slicing (e.g. a[0:10:2]).");

static void
slice_dealloc(PySliceObject *r)
{
    _PyObject_GC_UNTRACK(r);
    Py_DECREF(r->step);
    Py_DECREF(r->start);
    Py_DECREF(r->stop);
    if (slice_cache == NULL)
        slice_cache = r;
    else
        PyObject_GC_Del(r);
}

static PyObject *
slice_repr(PySliceObject *r)
{
    return PyUnicode_FromFormat("slice(%R, %R, %R)", r->start, r->stop, r->step);
}

static PyMemberDef slice_members[] = {
    {"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
    {"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
    {"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
    {0}
};

/* Helper function to convert a slice argument to a PyLong, and raise TypeError
   with a suitable message on failure. */

static PyObject*
evaluate_slice_index(PyObject *v)
{
    if (PyIndex_Check(v)) {
        return PyNumber_Index(v);
    }
    else {
        PyErr_SetString(PyExc_TypeError,
                        "slice indices must be integers or "
                        "None or have an __index__ method");
        return NULL;
    }
}

/* Compute slice indices given a slice and length.  Return -1 on failure.  Used
   by slice.indices and rangeobject slicing.  Assumes that `len` is a
   nonnegative instance of PyLong. */

int
_PySlice_GetLongIndices(PySliceObject *self, PyObject *length,
                        PyObject **start_ptr, PyObject **stop_ptr,
                        PyObject **step_ptr)
{
    PyObject *start=NULL, *stop=NULL, *step=NULL;
    PyObject *upper=NULL, *lower=NULL;
    int step_is_negative, cmp_result;

    /* Convert step to an integer; raise for zero step. */
    if (self->step == Py_None) {
        step = _PyLong_One;
        Py_INCREF(step);
        step_is_negative = 0;
    }
    else {
        int step_sign;
        step = evaluate_slice_index(self->step);
        if (step == NULL)
            goto error;
        step_sign = _PyLong_Sign(step);
        if (step_sign == 0) {
            PyErr_SetString(PyExc_ValueError,
                            "slice step cannot be zero");
            goto error;
        }
        step_is_negative = step_sign < 0;
    }

    /* Find lower and upper bounds for start and stop. */
    if (step_is_negative) {
        lower = PyLong_FromLong(-1L);
        if (lower == NULL)
            goto error;

        upper = PyNumber_Add(length, lower);
        if (upper == NULL)
            goto error;
    }
    else {
        lower = _PyLong_Zero;
        Py_INCREF(lower);
        upper = length;
        Py_INCREF(upper);
    }

    /* Compute start. */
    if (self->start == Py_None) {
        start = step_is_negative ? upper : lower;
        Py_INCREF(start);
    }
    else {
        start = evaluate_slice_index(self->start);
        if (start == NULL)
            goto error;

        if (_PyLong_Sign(start) < 0) {
            /* start += length */
            PyObject *tmp = PyNumber_Add(start, length);
            Py_DECREF(start);
            start = tmp;
            if (start == NULL)
                goto error;

            cmp_result = PyObject_RichCompareBool(start, lower, Py_LT);
            if (cmp_result < 0)
                goto error;
            if (cmp_result) {
                Py_INCREF(lower);
                Py_DECREF(start);
                start = lower;
            }
        }
        else {
            cmp_result = PyObject_RichCompareBool(start, upper, Py_GT);
            if (cmp_result < 0)
                goto error;
            if (cmp_result) {
                Py_INCREF(upper);
                Py_DECREF(start);
                start = upper;
            }
        }
    }

    /* Compute stop. */
    if (self->stop == Py_None) {
        stop = step_is_negative ? lower : upper;
        Py_INCREF(stop);
    }
    else {
        stop = evaluate_slice_index(self->stop);
        if (stop == NULL)
            goto error;

        if (_PyLong_Sign(stop) < 0) {
            /* stop += length */
            PyObject *tmp = PyNumber_Add(stop, length);
            Py_DECREF(stop);
            stop = tmp;
            if (stop == NULL)
                goto error;

            cmp_result = PyObject_RichCompareBool(stop, lower, Py_LT);
            if (cmp_result < 0)
                goto error;
            if (cmp_result) {
                Py_INCREF(lower);
                Py_DECREF(stop);
                stop = lower;
            }
        }
        else {
            cmp_result = PyObject_RichCompareBool(stop, upper, Py_GT);
            if (cmp_result < 0)
                goto error;
            if (cmp_result) {
                Py_INCREF(upper);
                Py_DECREF(stop);
                stop = upper;
            }
        }
    }

    *start_ptr = start;
    *stop_ptr = stop;
    *step_ptr = step;
    Py_DECREF(upper);
    Py_DECREF(lower);
    return 0;

  error:
    *start_ptr = *stop_ptr = *step_ptr = NULL;
    Py_XDECREF(start);
    Py_XDECREF(stop);
    Py_XDECREF(step);
    Py_XDECREF(upper);
    Py_XDECREF(lower);
    return -1;
}

/* Implementation of slice.indices. */

static PyObject*
slice_indices(PySliceObject* self, PyObject* len)
{
    PyObject *start, *stop, *step;
    PyObject *length;
    int error;

    /* Convert length to an integer if necessary; raise for negative length. */
    length = PyNumber_Index(len);
    if (length == NULL)
        return NULL;

    if (_PyLong_Sign(length) < 0) {
        PyErr_SetString(PyExc_ValueError,
                        "length should not be negative");
        Py_DECREF(length);
        return NULL;
    }

    error = _PySlice_GetLongIndices(self, length, &start, &stop, &step);
    Py_DECREF(length);
    if (error == -1)
        return NULL;
    else
        return Py_BuildValue("(NNN)", start, stop, step);
}

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 */
};

Coverage Report

Created: 2025-10-27 06:40

Line	Count	Source
1		/*
2		Written by Jim Hugunin and Chris Chase.
3
4		This includes both the singular ellipsis object and slice objects.
5
6		Guido, feel free to do whatever you want in the way of copyrights
7		for this file.
8		*/
9
10		/*
11		Py_Ellipsis encodes the '...' rubber index token. It is similar to
12		the Py_NoneStruct in that there is no way to create other objects of
13		this type and there is exactly one in existence.
14		*/
15
16		#include "Python.h"
17		#include "pycore_object.h"
18		#include "pycore_pymem.h"
19		#include "pycore_pystate.h"
20		#include "structmember.h"
21
22		static PyObject *
23		ellipsis_new(PyTypeObject type, PyObject args, PyObject *kwargs)
24	0	{
25	0	if (PyTuple_GET_SIZE(args) \|\| (kwargs && PyDict_GET_SIZE(kwargs))) {
26	0	PyErr_SetString(PyExc_TypeError, "EllipsisType takes no arguments");
27	0	return NULL;
28	0	}
29	0	Py_INCREF(Py_Ellipsis);
30	0	return Py_Ellipsis;
31	0	}
32
33		static PyObject *
34		ellipsis_repr(PyObject *op)
35	0	{
36	0	return PyUnicode_FromString("Ellipsis");
37	0	}
38
39		static PyObject *
40		ellipsis_reduce(PyObject op, PyObject Py_UNUSED(ignored))
41	0	{
42	0	return PyUnicode_FromString("Ellipsis");
43	0	}
44
45		static PyMethodDef ellipsis_methods[] = {
46		{"__reduce__", ellipsis_reduce, METH_NOARGS, NULL},
47		{NULL, NULL}
48		};
49
50		PyTypeObject PyEllipsis_Type = {
51		PyVarObject_HEAD_INIT(&PyType_Type, 0)
52		"ellipsis", /* tp_name */
53		0, /* tp_basicsize */
54		0, /* tp_itemsize */
55		0, /never called/ /* tp_dealloc */
56		0, /* tp_vectorcall_offset */
57		0, /* tp_getattr */
58		0, /* tp_setattr */
59		0, /* tp_as_async */
60		ellipsis_repr, /* tp_repr */
61		0, /* tp_as_number */
62		0, /* tp_as_sequence */
63		0, /* tp_as_mapping */
64		0, /* tp_hash */
65		0, /* tp_call */
66		0, /* tp_str */
67		PyObject_GenericGetAttr, /* tp_getattro */
68		0, /* tp_setattro */
69		0, /* tp_as_buffer */
70		Py_TPFLAGS_DEFAULT, /* tp_flags */
71		0, /* tp_doc */
72		0, /* tp_traverse */
73		0, /* tp_clear */
74		0, /* tp_richcompare */
75		0, /* tp_weaklistoffset */
76		0, /* tp_iter */
77		0, /* tp_iternext */
78		ellipsis_methods, /* tp_methods */
79		0, /* tp_members */
80		0, /* tp_getset */
81		0, /* tp_base */
82		0, /* tp_dict */
83		0, /* tp_descr_get */
84		0, /* tp_descr_set */
85		0, /* tp_dictoffset */
86		0, /* tp_init */
87		0, /* tp_alloc */
88		ellipsis_new, /* tp_new */
89		};
90
91		PyObject _Py_EllipsisObject = {
92		_PyObject_EXTRA_INIT
93		1, &PyEllipsis_Type
94		};
95
96
97		/* Slice object implementation */
98
99		/* Using a cache is very effective since typically only a single slice is
100		* created and then deleted again
101		*/
102		static PySliceObject *slice_cache = NULL;
103		void PySlice_Fini(void)
104	0	{
105	0	PySliceObject *obj = slice_cache;
106	0	if (obj != NULL) {
107	0	slice_cache = NULL;
108	0	PyObject_GC_Del(obj);
109	0	}
110	0	}
111
112		/* start, stop, and step are python objects with None indicating no
113		index is present.
114		*/
115
116		PyObject *
117		PySlice_New(PyObject start, PyObject stop, PyObject *step)
118	2.37k	{
119	2.37k	PySliceObject *obj;
120	2.37k	if (slice_cache != NULL) {
121	2.35k	obj = slice_cache;
122	2.35k	slice_cache = NULL;
123	2.35k	_Py_NewReference((PyObject *)obj);
124	2.35k	} else {
125	14	obj = PyObject_GC_New(PySliceObject, &PySlice_Type);
126	14	if (obj == NULL)
127	0	return NULL;
128	14	}
129
130	2.37k	if (step == NULL) step = Py_None;
131	2.37k	Py_INCREF(step);
132	2.37k	if (start == NULL) start = Py_None;
133	2.37k	Py_INCREF(start);
134	2.37k	if (stop == NULL) stop = Py_None;
135	2.37k	Py_INCREF(stop);
136
137	2.37k	obj->step = step;
138	2.37k	obj->start = start;
139	2.37k	obj->stop = stop;
140
141	2.37k	_PyObject_GC_TRACK(obj);
142	2.37k	return (PyObject *) obj;
143	2.37k	}
144
145		PyObject *
146		_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
147	0	{
148	0	PyObject start, end, *slice;
149	0	start = PyLong_FromSsize_t(istart);
150	0	if (!start)
151	0	return NULL;
152	0	end = PyLong_FromSsize_t(istop);
153	0	if (!end) {
154	0	Py_DECREF(start);
155	0	return NULL;
156	0	}
157
158	0	slice = PySlice_New(start, end, NULL);
159	0	Py_DECREF(start);
160	0	Py_DECREF(end);
161	0	return slice;
162	0	}
163
164		int
165		PySlice_GetIndices(PyObject *_r, Py_ssize_t length,
166		Py_ssize_t start, Py_ssize_t stop, Py_ssize_t *step)
167	0	{
168	0	PySliceObject r = (PySliceObject)_r;
169		/* XXX support long ints */
170	0	if (r->step == Py_None) {
171	0	*step = 1;
172	0	} else {
173	0	if (!PyLong_Check(r->step)) return -1;
174	0	*step = PyLong_AsSsize_t(r->step);
175	0	}
176	0	if (r->start == Py_None) {
177	0	start = step < 0 ? length-1 : 0;
178	0	} else {
179	0	if (!PyLong_Check(r->start)) return -1;
180	0	*start = PyLong_AsSsize_t(r->start);
181	0	if (start < 0) start += length;
182	0	}
183	0	if (r->stop == Py_None) {
184	0	stop = step < 0 ? -1 : length;
185	0	} else {
186	0	if (!PyLong_Check(r->stop)) return -1;
187	0	*stop = PyLong_AsSsize_t(r->stop);
188	0	if (stop < 0) stop += length;
189	0	}
190	0	if (*stop > length) return -1;
191	0	if (*start >= length) return -1;
192	0	if (*step == 0) return -1;
193	0	return 0;
194	0	}
195
196		int
197		PySlice_Unpack(PyObject *_r,
198		Py_ssize_t start, Py_ssize_t stop, Py_ssize_t *step)
199	2.33k	{
200	2.33k	PySliceObject r = (PySliceObject)_r;
201		/* this is harder to get right than you might think */
202
203	2.33k	Py_BUILD_ASSERT(PY_SSIZE_T_MIN + 1 <= -PY_SSIZE_T_MAX);
204
205	2.33k	if (r->step == Py_None) {
206	2.32k	*step = 1;
207	2.32k	}
208	9	else {
209	9	if (!_PyEval_SliceIndex(r->step, step)) return -1;
210	9	if (*step == 0) {
211	0	PyErr_SetString(PyExc_ValueError,
212	0	"slice step cannot be zero");
213	0	return -1;
214	0	}
215		/* Here *step might be -PY_SSIZE_T_MAX-1; in this case we replace it
216		* with -PY_SSIZE_T_MAX. This doesn't affect the semantics, and it
217		* guards against later undefined behaviour resulting from code that
218		* does "step = -step" as part of a slice reversal.
219		*/
220	9	if (*step < -PY_SSIZE_T_MAX)
221	0	*step = -PY_SSIZE_T_MAX;
222	9	}
223
224	2.33k	if (r->start == Py_None) {
225	516	start = step < 0 ? PY_SSIZE_T_MAX : 0;
226	516	}
227	1.82k	else {
228	1.82k	if (!_PyEval_SliceIndex(r->start, start)) return -1;
229	1.82k	}
230
231	2.33k	if (r->stop == Py_None) {
232	444	stop = step < 0 ? PY_SSIZE_T_MIN : PY_SSIZE_T_MAX;
233	444	}
234	1.89k	else {
235	1.89k	if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
236	1.89k	}
237
238	2.33k	return 0;
239	2.33k	}
240
241		Py_ssize_t
242		PySlice_AdjustIndices(Py_ssize_t length,
243		Py_ssize_t start, Py_ssize_t stop, Py_ssize_t step)
244	2.33k	{
245		/* this is harder to get right than you might think */
246
247	2.33k	assert(step != 0);
248	2.33k	assert(step >= -PY_SSIZE_T_MAX);
249
250	2.33k	if (*start < 0) {
251	124	*start += length;
252	124	if (*start < 0) {
253	0	*start = (step < 0) ? -1 : 0;
254	0	}
255	124	}
256	2.21k	else if (*start >= length) {
257	26	*start = (step < 0) ? length - 1 : length;
258	26	}
259
260	2.33k	if (*stop < 0) {
261	36	*stop += length;
262	36	if (*stop < 0) {
263	9	*stop = (step < 0) ? -1 : 0;
264	9	}
265	36	}
266	2.30k	else if (*stop >= length) {
267	459	*stop = (step < 0) ? length - 1 : length;
268	459	}
269
270	2.33k	if (step < 0) {
271	9	if (stop < start) {
272	9	return (start - stop - 1) / (-step) + 1;
273	9	}
274	9	}
275	2.32k	else {
276	2.32k	if (start < stop) {
277	2.25k	return (stop - start - 1) / step + 1;
278	2.25k	}
279	2.32k	}
280	75	return 0;
281	2.33k	}
282
283		#undef PySlice_GetIndicesEx
284
285		int
286		PySlice_GetIndicesEx(PyObject *_r, Py_ssize_t length,
287		Py_ssize_t start, Py_ssize_t stop, Py_ssize_t *step,
288		Py_ssize_t *slicelength)
289	0	{
290	0	if (PySlice_Unpack(_r, start, stop, step) < 0)
291	0	return -1;
292	0	slicelength = PySlice_AdjustIndices(length, start, stop, step);
293	0	return 0;
294	0	}
295
296		static PyObject *
297		slice_new(PyTypeObject type, PyObject args, PyObject *kw)
298	0	{
299	0	PyObject start, stop, *step;
300
301	0	start = stop = step = NULL;
302
303	0	if (!_PyArg_NoKeywords("slice", kw))
304	0	return NULL;
305
306	0	if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
307	0	return NULL;
308
309		/* This swapping of stop and start is to maintain similarity with
310		range(). */
311	0	if (stop == NULL) {
312	0	stop = start;
313	0	start = NULL;
314	0	}
315	0	return PySlice_New(start, stop, step);
316	0	}
317
318		PyDoc_STRVAR(slice_doc,
319		"slice(stop)\n\
320		slice(start, stop[, step])\n\
321		\n\
322		Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
323
324		static void
325		slice_dealloc(PySliceObject *r)
326	2.37k	{
327	2.37k	_PyObject_GC_UNTRACK(r);
328	2.37k	Py_DECREF(r->step);
329	2.37k	Py_DECREF(r->start);
330	2.37k	Py_DECREF(r->stop);
331	2.37k	if (slice_cache == NULL)
332	2.37k	slice_cache = r;
333	0	else
334	0	PyObject_GC_Del(r);
335	2.37k	}
336
337		static PyObject *
338		slice_repr(PySliceObject *r)
339	0	{
340	0	return PyUnicode_FromFormat("slice(%R, %R, %R)", r->start, r->stop, r->step);
341	0	}
342
343		static PyMemberDef slice_members[] = {
344		{"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
345		{"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
346		{"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
347		{0}
348		};
349
350		/* Helper function to convert a slice argument to a PyLong, and raise TypeError
351		with a suitable message on failure. */
352
353		static PyObject*
354		evaluate_slice_index(PyObject *v)
355	36	{
356	36	if (PyIndex_Check(v)) {
357	36	return PyNumber_Index(v);
358	36	}
359	0	else {
360	0	PyErr_SetString(PyExc_TypeError,
361	0	"slice indices must be integers or "
362	0	"None or have an __index__ method");
363	0	return NULL;
364	0	}
365	36	}
366
367		/* Compute slice indices given a slice and length. Return -1 on failure. Used
368		by slice.indices and rangeobject slicing. Assumes that `len` is a
369		nonnegative instance of PyLong. */
370
371		int
372		_PySlice_GetLongIndices(PySliceObject self, PyObject length,
373		PyObject start_ptr, PyObject stop_ptr,
374		PyObject **step_ptr)
375	36	{
376	36	PyObject start=NULL, stop=NULL, *step=NULL;
377	36	PyObject upper=NULL, lower=NULL;
378	36	int step_is_negative, cmp_result;
379
380		/* Convert step to an integer; raise for zero step. */
381	36	if (self->step == Py_None) {
382	0	step = _PyLong_One;
383	0	Py_INCREF(step);
384	0	step_is_negative = 0;
385	0	}
386	36	else {
387	36	int step_sign;
388	36	step = evaluate_slice_index(self->step);
389	36	if (step == NULL)
390	0	goto error;
391	36	step_sign = _PyLong_Sign(step);
392	36	if (step_sign == 0) {
393	0	PyErr_SetString(PyExc_ValueError,
394	0	"slice step cannot be zero");
395	0	goto error;
396	0	}
397	36	step_is_negative = step_sign < 0;
398	36	}
399
400		/* Find lower and upper bounds for start and stop. */
401	36	if (step_is_negative) {
402	36	lower = PyLong_FromLong(-1L);
403	36	if (lower == NULL)
404	0	goto error;
405
406	36	upper = PyNumber_Add(length, lower);
407	36	if (upper == NULL)
408	0	goto error;
409	36	}
410	0	else {
411	0	lower = _PyLong_Zero;
412	0	Py_INCREF(lower);
413	0	upper = length;
414	0	Py_INCREF(upper);
415	0	}
416
417		/* Compute start. */
418	36	if (self->start == Py_None) {
419	36	start = step_is_negative ? upper : lower;
420	36	Py_INCREF(start);
421	36	}
422	0	else {
423	0	start = evaluate_slice_index(self->start);
424	0	if (start == NULL)
425	0	goto error;
426
427	0	if (_PyLong_Sign(start) < 0) {
428		/* start += length */
429	0	PyObject *tmp = PyNumber_Add(start, length);
430	0	Py_DECREF(start);
431	0	start = tmp;
432	0	if (start == NULL)
433	0	goto error;
434
435	0	cmp_result = PyObject_RichCompareBool(start, lower, Py_LT);
436	0	if (cmp_result < 0)
437	0	goto error;
438	0	if (cmp_result) {
439	0	Py_INCREF(lower);
440	0	Py_DECREF(start);
441	0	start = lower;
442	0	}
443	0	}
444	0	else {
445	0	cmp_result = PyObject_RichCompareBool(start, upper, Py_GT);
446	0	if (cmp_result < 0)
447	0	goto error;
448	0	if (cmp_result) {
449	0	Py_INCREF(upper);
450	0	Py_DECREF(start);
451	0	start = upper;
452	0	}
453	0	}
454	0	}
455
456		/* Compute stop. */
457	36	if (self->stop == Py_None) {
458	36	stop = step_is_negative ? lower : upper;
459	36	Py_INCREF(stop);
460	36	}
461	0	else {
462	0	stop = evaluate_slice_index(self->stop);
463	0	if (stop == NULL)
464	0	goto error;
465
466	0	if (_PyLong_Sign(stop) < 0) {
467		/* stop += length */
468	0	PyObject *tmp = PyNumber_Add(stop, length);
469	0	Py_DECREF(stop);
470	0	stop = tmp;
471	0	if (stop == NULL)
472	0	goto error;
473
474	0	cmp_result = PyObject_RichCompareBool(stop, lower, Py_LT);
475	0	if (cmp_result < 0)
476	0	goto error;
477	0	if (cmp_result) {
478	0	Py_INCREF(lower);
479	0	Py_DECREF(stop);
480	0	stop = lower;
481	0	}
482	0	}
483	0	else {
484	0	cmp_result = PyObject_RichCompareBool(stop, upper, Py_GT);
485	0	if (cmp_result < 0)
486	0	goto error;
487	0	if (cmp_result) {
488	0	Py_INCREF(upper);
489	0	Py_DECREF(stop);
490	0	stop = upper;
491	0	}
492	0	}
493	0	}
494
495	36	*start_ptr = start;
496	36	*stop_ptr = stop;
497	36	*step_ptr = step;
498	36	Py_DECREF(upper);
499	36	Py_DECREF(lower);
500	36	return 0;
501
502	0	error:
503	0	start_ptr = stop_ptr = *step_ptr = NULL;
504	0	Py_XDECREF(start);
505	0	Py_XDECREF(stop);
506	0	Py_XDECREF(step);
507	0	Py_XDECREF(upper);
508	0	Py_XDECREF(lower);
509	0	return -1;
510	36	}
511
512		/* Implementation of slice.indices. */
513
514		static PyObject*
515		slice_indices(PySliceObject* self, PyObject* len)
516	0	{
517	0	PyObject start, stop, *step;
518	0	PyObject *length;
519	0	int error;
520
521		/* Convert length to an integer if necessary; raise for negative length. */
522	0	length = PyNumber_Index(len);
523	0	if (length == NULL)
524	0	return NULL;
525
526	0	if (_PyLong_Sign(length) < 0) {
527	0	PyErr_SetString(PyExc_ValueError,
528	0	"length should not be negative");
529	0	Py_DECREF(length);
530	0	return NULL;
531	0	}
532
533	0	error = _PySlice_GetLongIndices(self, length, &start, &stop, &step);
534	0	Py_DECREF(length);
535	0	if (error == -1)
536	0	return NULL;
537	0	else
538	0	return Py_BuildValue("(NNN)", start, stop, step);
539	0	}
540
541		PyDoc_STRVAR(slice_indices_doc,
542		"S.indices(len) -> (start, stop, stride)\n\
543		\n\
544		Assuming a sequence of length len, calculate the start and stop\n\
545		indices, and the stride length of the extended slice described by\n\
546		S. Out of bounds indices are clipped in a manner consistent with the\n\
547		handling of normal slices.");
548
549		static PyObject *
550		slice_reduce(PySliceObject* self, PyObject *Py_UNUSED(ignored))
551	0	{
552	0	return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
553	0	}
554
555		PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
556
557		static PyMethodDef slice_methods[] = {
558		{"indices", (PyCFunction)slice_indices,
559		METH_O, slice_indices_doc},
560		{"__reduce__", (PyCFunction)slice_reduce,
561		METH_NOARGS, reduce_doc},
562		{NULL, NULL}
563		};
564
565		static PyObject *
566		slice_richcompare(PyObject v, PyObject w, int op)
567	0	{
568	0	if (!PySlice_Check(v) \|\| !PySlice_Check(w))
569	0	Py_RETURN_NOTIMPLEMENTED;
570
571	0	if (v == w) {
572	0	PyObject *res;
573		/* XXX Do we really need this shortcut?
574		There's a unit test for it, but is that fair? */
575	0	switch (op) {
576	0	case Py_EQ:
577	0	case Py_LE:
578	0	case Py_GE:
579	0	res = Py_True;
580	0	break;
581	0	default:
582	0	res = Py_False;
583	0	break;
584	0	}
585	0	Py_INCREF(res);
586	0	return res;
587	0	}
588
589
590	0	PyObject *t1 = PyTuple_Pack(3,
591	0	((PySliceObject *)v)->start,
592	0	((PySliceObject *)v)->stop,
593	0	((PySliceObject *)v)->step);
594	0	if (t1 == NULL) {
595	0	return NULL;
596	0	}
597
598	0	PyObject *t2 = PyTuple_Pack(3,
599	0	((PySliceObject *)w)->start,
600	0	((PySliceObject *)w)->stop,
601	0	((PySliceObject *)w)->step);
602	0	if (t2 == NULL) {
603	0	Py_DECREF(t1);
604	0	return NULL;
605	0	}
606
607	0	PyObject *res = PyObject_RichCompare(t1, t2, op);
608	0	Py_DECREF(t1);
609	0	Py_DECREF(t2);
610	0	return res;
611	0	}
612
613		static int
614		slice_traverse(PySliceObject v, visitproc visit, void arg)
615	0	{
616	0	Py_VISIT(v->start);
617	0	Py_VISIT(v->stop);
618	0	Py_VISIT(v->step);
619	0	return 0;
620	0	}
621
622		PyTypeObject PySlice_Type = {
623		PyVarObject_HEAD_INIT(&PyType_Type, 0)
624		"slice", /* Name of this type */
625		sizeof(PySliceObject), /* Basic object size */
626		0, /* Item size for varobject */
627		(destructor)slice_dealloc, /* tp_dealloc */
628		0, /* tp_vectorcall_offset */
629		0, /* tp_getattr */
630		0, /* tp_setattr */
631		0, /* tp_as_async */
632		(reprfunc)slice_repr, /* tp_repr */
633		0, /* tp_as_number */
634		0, /* tp_as_sequence */
635		0, /* tp_as_mapping */
636		PyObject_HashNotImplemented, /* tp_hash */
637		0, /* tp_call */
638		0, /* tp_str */
639		PyObject_GenericGetAttr, /* tp_getattro */
640		0, /* tp_setattro */
641		0, /* tp_as_buffer */
642		Py_TPFLAGS_DEFAULT \| Py_TPFLAGS_HAVE_GC, /* tp_flags */
643		slice_doc, /* tp_doc */
644		(traverseproc)slice_traverse, /* tp_traverse */
645		0, /* tp_clear */
646		slice_richcompare, /* tp_richcompare */
647		0, /* tp_weaklistoffset */
648		0, /* tp_iter */
649		0, /* tp_iternext */
650		slice_methods, /* tp_methods */
651		slice_members, /* tp_members */
652		0, /* tp_getset */
653		0, /* tp_base */
654		0, /* tp_dict */
655		0, /* tp_descr_get */
656		0, /* tp_descr_set */
657		0, /* tp_dictoffset */
658		0, /* tp_init */
659		0, /* tp_alloc */
660		slice_new, /* tp_new */
661		};