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 *
ellipsis_repr(PyObject * op)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 *
PySlice_New(PyObject * start,PyObject * stop,PyObject * step)61 PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
62 {
63 PySliceObject *obj = PyObject_GC_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 _PyObject_GC_TRACK(obj);
80 return (PyObject *) obj;
81 }
82
83 PyObject *
_PySlice_FromIndices(Py_ssize_t istart,Py_ssize_t istop)84 _PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
85 {
86 PyObject *start, *end, *slice;
87 start = PyInt_FromSsize_t(istart);
88 if (!start)
89 return NULL;
90 end = PyInt_FromSsize_t(istop);
91 if (!end) {
92 Py_DECREF(start);
93 return NULL;
94 }
95
96 slice = PySlice_New(start, end, NULL);
97 Py_DECREF(start);
98 Py_DECREF(end);
99 return slice;
100 }
101
102 int
PySlice_GetIndices(PySliceObject * r,Py_ssize_t length,Py_ssize_t * start,Py_ssize_t * stop,Py_ssize_t * step)103 PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
104 Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
105 {
106 /* XXX support long ints */
107 if (r->step == Py_None) {
108 *step = 1;
109 } else {
110 if (!PyInt_Check(r->step) && !PyLong_Check(r->step)) return -1;
111 *step = PyInt_AsSsize_t(r->step);
112 }
113 if (r->start == Py_None) {
114 *start = *step < 0 ? length-1 : 0;
115 } else {
116 if (!PyInt_Check(r->start) && !PyLong_Check(r->step)) return -1;
117 *start = PyInt_AsSsize_t(r->start);
118 if (*start < 0) *start += length;
119 }
120 if (r->stop == Py_None) {
121 *stop = *step < 0 ? -1 : length;
122 } else {
123 if (!PyInt_Check(r->stop) && !PyLong_Check(r->step)) return -1;
124 *stop = PyInt_AsSsize_t(r->stop);
125 if (*stop < 0) *stop += length;
126 }
127 if (*stop > length) return -1;
128 if (*start >= length) return -1;
129 if (*step == 0) return -1;
130 return 0;
131 }
132
133 int
PySlice_GetIndicesEx(PySliceObject * r,Py_ssize_t length,Py_ssize_t * start,Py_ssize_t * stop,Py_ssize_t * step,Py_ssize_t * slicelength)134 PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length,
135 Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)
136 {
137 /* this is harder to get right than you might think */
138
139 Py_ssize_t defstart, defstop;
140
141 if (r->step == Py_None) {
142 *step = 1;
143 }
144 else {
145 if (!_PyEval_SliceIndex(r->step, step)) return -1;
146 if (*step == 0) {
147 PyErr_SetString(PyExc_ValueError,
148 "slice step cannot be zero");
149 return -1;
150 }
151 }
152
153 defstart = *step < 0 ? length-1 : 0;
154 defstop = *step < 0 ? -1 : length;
155
156 if (r->start == Py_None) {
157 *start = defstart;
158 }
159 else {
160 if (!_PyEval_SliceIndex(r->start, start)) return -1;
161 if (*start < 0) *start += length;
162 if (*start < 0) *start = (*step < 0) ? -1 : 0;
163 if (*start >= length)
164 *start = (*step < 0) ? length - 1 : length;
165 }
166
167 if (r->stop == Py_None) {
168 *stop = defstop;
169 }
170 else {
171 if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
172 if (*stop < 0) *stop += length;
173 if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
174 if (*stop >= length)
175 *stop = (*step < 0) ? length - 1 : length;
176 }
177
178 if ((*step < 0 && *stop >= *start)
179 || (*step > 0 && *start >= *stop)) {
180 *slicelength = 0;
181 }
182 else if (*step < 0) {
183 *slicelength = (*stop-*start+1)/(*step)+1;
184 }
185 else {
186 *slicelength = (*stop-*start-1)/(*step)+1;
187 }
188
189 return 0;
190 }
191
192 static PyObject *
slice_new(PyTypeObject * type,PyObject * args,PyObject * kw)193 slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
194 {
195 PyObject *start, *stop, *step;
196
197 start = stop = step = NULL;
198
199 if (!_PyArg_NoKeywords("slice()", kw))
200 return NULL;
201
202 if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
203 return NULL;
204
205 /* This swapping of stop and start is to maintain similarity with
206 range(). */
207 if (stop == NULL) {
208 stop = start;
209 start = NULL;
210 }
211 return PySlice_New(start, stop, step);
212 }
213
214 PyDoc_STRVAR(slice_doc,
215 "slice(stop)\n\
216 slice(start, stop[, step])\n\
217 \n\
218 Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
219
220 static void
slice_dealloc(PySliceObject * r)221 slice_dealloc(PySliceObject *r)
222 {
223 _PyObject_GC_UNTRACK(r);
224 Py_DECREF(r->step);
225 Py_DECREF(r->start);
226 Py_DECREF(r->stop);
227 PyObject_GC_Del(r);
228 }
229
230 static PyObject *
slice_repr(PySliceObject * r)231 slice_repr(PySliceObject *r)
232 {
233 PyObject *s, *comma;
234
235 s = PyString_FromString("slice(");
236 comma = PyString_FromString(", ");
237 PyString_ConcatAndDel(&s, PyObject_Repr(r->start));
238 PyString_Concat(&s, comma);
239 PyString_ConcatAndDel(&s, PyObject_Repr(r->stop));
240 PyString_Concat(&s, comma);
241 PyString_ConcatAndDel(&s, PyObject_Repr(r->step));
242 PyString_ConcatAndDel(&s, PyString_FromString(")"));
243 Py_DECREF(comma);
244 return s;
245 }
246
247 static PyMemberDef slice_members[] = {
248 {"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
249 {"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
250 {"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
251 {0}
252 };
253
254 static PyObject*
slice_indices(PySliceObject * self,PyObject * len)255 slice_indices(PySliceObject* self, PyObject* len)
256 {
257 Py_ssize_t ilen, start, stop, step, slicelength;
258
259 ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
260
261 if (ilen == -1 && PyErr_Occurred()) {
262 return NULL;
263 }
264
265 if (PySlice_GetIndicesEx(self, ilen, &start, &stop,
266 &step, &slicelength) < 0) {
267 return NULL;
268 }
269
270 return Py_BuildValue("(nnn)", start, stop, step);
271 }
272
273 PyDoc_STRVAR(slice_indices_doc,
274 "S.indices(len) -> (start, stop, stride)\n\
275 \n\
276 Assuming a sequence of length len, calculate the start and stop\n\
277 indices, and the stride length of the extended slice described by\n\
278 S. Out of bounds indices are clipped in a manner consistent with the\n\
279 handling of normal slices.");
280
281 static PyObject *
slice_reduce(PySliceObject * self)282 slice_reduce(PySliceObject* self)
283 {
284 return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
285 }
286
287 PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
288
289 static PyMethodDef slice_methods[] = {
290 {"indices", (PyCFunction)slice_indices,
291 METH_O, slice_indices_doc},
292 {"__reduce__", (PyCFunction)slice_reduce,
293 METH_NOARGS, reduce_doc},
294 {NULL, NULL}
295 };
296
297 static int
slice_compare(PySliceObject * v,PySliceObject * w)298 slice_compare(PySliceObject *v, PySliceObject *w)
299 {
300 int result = 0;
301
302 if (v == w)
303 return 0;
304
305 if (PyObject_Cmp(v->start, w->start, &result) < 0)
306 return -2;
307 if (result != 0)
308 return result;
309 if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
310 return -2;
311 if (result != 0)
312 return result;
313 if (PyObject_Cmp(v->step, w->step, &result) < 0)
314 return -2;
315 return result;
316 }
317
318 static long
slice_hash(PySliceObject * v)319 slice_hash(PySliceObject *v)
320 {
321 PyErr_SetString(PyExc_TypeError, "unhashable type");
322 return -1L;
323 }
324
325 static int
slice_traverse(PySliceObject * v,visitproc visit,void * arg)326 slice_traverse(PySliceObject *v, visitproc visit, void *arg)
327 {
328 Py_VISIT(v->start);
329 Py_VISIT(v->stop);
330 Py_VISIT(v->step);
331 return 0;
332 }
333
334 PyTypeObject PySlice_Type = {
335 PyVarObject_HEAD_INIT(&PyType_Type, 0)
336 "slice", /* Name of this type */
337 sizeof(PySliceObject), /* Basic object size */
338 0, /* Item size for varobject */
339 (destructor)slice_dealloc, /* tp_dealloc */
340 0, /* tp_print */
341 0, /* tp_getattr */
342 0, /* tp_setattr */
343 (cmpfunc)slice_compare, /* tp_compare */
344 (reprfunc)slice_repr, /* tp_repr */
345 0, /* tp_as_number */
346 0, /* tp_as_sequence */
347 0, /* tp_as_mapping */
348 (hashfunc)slice_hash, /* tp_hash */
349 0, /* tp_call */
350 0, /* tp_str */
351 PyObject_GenericGetAttr, /* tp_getattro */
352 0, /* tp_setattro */
353 0, /* tp_as_buffer */
354 Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
355 slice_doc, /* tp_doc */
356 (traverseproc)slice_traverse, /* tp_traverse */
357 0, /* tp_clear */
358 0, /* tp_richcompare */
359 0, /* tp_weaklistoffset */
360 0, /* tp_iter */
361 0, /* tp_iternext */
362 slice_methods, /* tp_methods */
363 slice_members, /* tp_members */
364 0, /* tp_getset */
365 0, /* tp_base */
366 0, /* tp_dict */
367 0, /* tp_descr_get */
368 0, /* tp_descr_set */
369 0, /* tp_dictoffset */
370 0, /* tp_init */
371 0, /* tp_alloc */
372 slice_new, /* tp_new */
373 };
374