No issues found
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 "structmember.h"
18
19 static PyObject *
20 ellipsis_repr(PyObject *op)
21 {
22 return PyString_FromString("Ellipsis");
23 }
24
25 PyTypeObject PyEllipsis_Type = {
26 PyVarObject_HEAD_INIT(&PyType_Type, 0)
27 "ellipsis", /* tp_name */
28 0, /* tp_basicsize */
29 0, /* tp_itemsize */
30 0, /*never called*/ /* tp_dealloc */
31 0, /* tp_print */
32 0, /* tp_getattr */
33 0, /* tp_setattr */
34 0, /* tp_compare */
35 ellipsis_repr, /* tp_repr */
36 0, /* tp_as_number */
37 0, /* tp_as_sequence */
38 0, /* tp_as_mapping */
39 0, /* tp_hash */
40 0, /* tp_call */
41 0, /* tp_str */
42 PyObject_GenericGetAttr, /* tp_getattro */
43 0, /* tp_setattro */
44 0, /* tp_as_buffer */
45 Py_TPFLAGS_DEFAULT, /* tp_flags */
46 };
47
48 PyObject _Py_EllipsisObject = {
49 _PyObject_EXTRA_INIT
50 1, &PyEllipsis_Type
51 };
52
53
54 /* Slice object implementation
55
56 start, stop, and step are python objects with None indicating no
57 index is present.
58 */
59
60 PyObject *
61 PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
62 {
63 PySliceObject *obj = PyObject_New(PySliceObject, &PySlice_Type);
64
65 if (obj == NULL)
66 return NULL;
67
68 if (step == NULL) step = Py_None;
69 Py_INCREF(step);
70 if (start == NULL) start = Py_None;
71 Py_INCREF(start);
72 if (stop == NULL) stop = Py_None;
73 Py_INCREF(stop);
74
75 obj->step = step;
76 obj->start = start;
77 obj->stop = stop;
78
79 return (PyObject *) obj;
80 }
81
82 PyObject *
83 _PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
84 {
85 PyObject *start, *end, *slice;
86 start = PyInt_FromSsize_t(istart);
87 if (!start)
88 return NULL;
89 end = PyInt_FromSsize_t(istop);
90 if (!end) {
91 Py_DECREF(start);
92 return NULL;
93 }
94
95 slice = PySlice_New(start, end, NULL);
96 Py_DECREF(start);
97 Py_DECREF(end);
98 return slice;
99 }
100
101 int
102 PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
103 Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
104 {
105 /* XXX support long ints */
106 if (r->step == Py_None) {
107 *step = 1;
108 } else {
109 if (!PyInt_Check(r->step) && !PyLong_Check(r->step)) return -1;
110 *step = PyInt_AsSsize_t(r->step);
111 }
112 if (r->start == Py_None) {
113 *start = *step < 0 ? length-1 : 0;
114 } else {
115 if (!PyInt_Check(r->start) && !PyLong_Check(r->step)) return -1;
116 *start = PyInt_AsSsize_t(r->start);
117 if (*start < 0) *start += length;
118 }
119 if (r->stop == Py_None) {
120 *stop = *step < 0 ? -1 : length;
121 } else {
122 if (!PyInt_Check(r->stop) && !PyLong_Check(r->step)) return -1;
123 *stop = PyInt_AsSsize_t(r->stop);
124 if (*stop < 0) *stop += length;
125 }
126 if (*stop > length) return -1;
127 if (*start >= length) return -1;
128 if (*step == 0) return -1;
129 return 0;
130 }
131
132 int
133 PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length,
134 Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)
135 {
136 /* this is harder to get right than you might think */
137
138 Py_ssize_t defstart, defstop;
139
140 if (r->step == Py_None) {
141 *step = 1;
142 }
143 else {
144 if (!_PyEval_SliceIndex(r->step, step)) return -1;
145 if (*step == 0) {
146 PyErr_SetString(PyExc_ValueError,
147 "slice step cannot be zero");
148 return -1;
149 }
150 }
151
152 defstart = *step < 0 ? length-1 : 0;
153 defstop = *step < 0 ? -1 : length;
154
155 if (r->start == Py_None) {
156 *start = defstart;
157 }
158 else {
159 if (!_PyEval_SliceIndex(r->start, start)) return -1;
160 if (*start < 0) *start += length;
161 if (*start < 0) *start = (*step < 0) ? -1 : 0;
162 if (*start >= length)
163 *start = (*step < 0) ? length - 1 : length;
164 }
165
166 if (r->stop == Py_None) {
167 *stop = defstop;
168 }
169 else {
170 if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
171 if (*stop < 0) *stop += length;
172 if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
173 if (*stop >= length)
174 *stop = (*step < 0) ? length - 1 : length;
175 }
176
177 if ((*step < 0 && *stop >= *start)
178 || (*step > 0 && *start >= *stop)) {
179 *slicelength = 0;
180 }
181 else if (*step < 0) {
182 *slicelength = (*stop-*start+1)/(*step)+1;
183 }
184 else {
185 *slicelength = (*stop-*start-1)/(*step)+1;
186 }
187
188 return 0;
189 }
190
191 static PyObject *
192 slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
193 {
194 PyObject *start, *stop, *step;
195
196 start = stop = step = NULL;
197
198 if (!_PyArg_NoKeywords("slice()", kw))
199 return NULL;
200
201 if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
202 return NULL;
203
204 /* This swapping of stop and start is to maintain similarity with
205 range(). */
206 if (stop == NULL) {
207 stop = start;
208 start = NULL;
209 }
210 return PySlice_New(start, stop, step);
211 }
212
213 PyDoc_STRVAR(slice_doc,
214 "slice([start,] stop[, step])\n\
215 \n\
216 Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
217
218 static void
219 slice_dealloc(PySliceObject *r)
220 {
221 Py_DECREF(r->step);
222 Py_DECREF(r->start);
223 Py_DECREF(r->stop);
224 PyObject_Del(r);
225 }
226
227 static PyObject *
228 slice_repr(PySliceObject *r)
229 {
230 PyObject *s, *comma;
231
232 s = PyString_FromString("slice(");
233 comma = PyString_FromString(", ");
234 PyString_ConcatAndDel(&s, PyObject_Repr(r->start));
235 PyString_Concat(&s, comma);
236 PyString_ConcatAndDel(&s, PyObject_Repr(r->stop));
237 PyString_Concat(&s, comma);
238 PyString_ConcatAndDel(&s, PyObject_Repr(r->step));
239 PyString_ConcatAndDel(&s, PyString_FromString(")"));
240 Py_DECREF(comma);
241 return s;
242 }
243
244 static PyMemberDef slice_members[] = {
245 {"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
246 {"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
247 {"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
248 {0}
249 };
250
251 static PyObject*
252 slice_indices(PySliceObject* self, PyObject* len)
253 {
254 Py_ssize_t ilen, start, stop, step, slicelength;
255
256 ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
257
258 if (ilen == -1 && PyErr_Occurred()) {
259 return NULL;
260 }
261
262 if (PySlice_GetIndicesEx(self, ilen, &start, &stop,
263 &step, &slicelength) < 0) {
264 return NULL;
265 }
266
267 return Py_BuildValue("(nnn)", start, stop, step);
268 }
269
270 PyDoc_STRVAR(slice_indices_doc,
271 "S.indices(len) -> (start, stop, stride)\n\
272 \n\
273 Assuming a sequence of length len, calculate the start and stop\n\
274 indices, and the stride length of the extended slice described by\n\
275 S. Out of bounds indices are clipped in a manner consistent with the\n\
276 handling of normal slices.");
277
278 static PyObject *
279 slice_reduce(PySliceObject* self)
280 {
281 return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
282 }
283
284 PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
285
286 static PyMethodDef slice_methods[] = {
287 {"indices", (PyCFunction)slice_indices,
288 METH_O, slice_indices_doc},
289 {"__reduce__", (PyCFunction)slice_reduce,
290 METH_NOARGS, reduce_doc},
291 {NULL, NULL}
292 };
293
294 static int
295 slice_compare(PySliceObject *v, PySliceObject *w)
296 {
297 int result = 0;
298
299 if (v == w)
300 return 0;
301
302 if (PyObject_Cmp(v->start, w->start, &result) < 0)
303 return -2;
304 if (result != 0)
305 return result;
306 if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
307 return -2;
308 if (result != 0)
309 return result;
310 if (PyObject_Cmp(v->step, w->step, &result) < 0)
311 return -2;
312 return result;
313 }
314
315 static long
316 slice_hash(PySliceObject *v)
317 {
318 PyErr_SetString(PyExc_TypeError, "unhashable type");
319 return -1L;
320 }
321
322 PyTypeObject PySlice_Type = {
323 PyVarObject_HEAD_INIT(&PyType_Type, 0)
324 "slice", /* Name of this type */
325 sizeof(PySliceObject), /* Basic object size */
326 0, /* Item size for varobject */
327 (destructor)slice_dealloc, /* tp_dealloc */
328 0, /* tp_print */
329 0, /* tp_getattr */
330 0, /* tp_setattr */
331 (cmpfunc)slice_compare, /* tp_compare */
332 (reprfunc)slice_repr, /* tp_repr */
333 0, /* tp_as_number */
334 0, /* tp_as_sequence */
335 0, /* tp_as_mapping */
336 (hashfunc)slice_hash, /* tp_hash */
337 0, /* tp_call */
338 0, /* tp_str */
339 PyObject_GenericGetAttr, /* tp_getattro */
340 0, /* tp_setattro */
341 0, /* tp_as_buffer */
342 Py_TPFLAGS_DEFAULT, /* tp_flags */
343 slice_doc, /* tp_doc */
344 0, /* tp_traverse */
345 0, /* tp_clear */
346 0, /* tp_richcompare */
347 0, /* tp_weaklistoffset */
348 0, /* tp_iter */
349 0, /* tp_iternext */
350 slice_methods, /* tp_methods */
351 slice_members, /* tp_members */
352 0, /* tp_getset */
353 0, /* tp_base */
354 0, /* tp_dict */
355 0, /* tp_descr_get */
356 0, /* tp_descr_set */
357 0, /* tp_dictoffset */
358 0, /* tp_init */
359 0, /* tp_alloc */
360 slice_new, /* tp_new */
361 };