sliceobject.c 6.54 KB
Newer Older
Guido van Rossum's avatar
Guido van Rossum committed
1 2 3
/*
Written by Jim Hugunin and Chris Chase.

4
This includes both the singular ellipsis object and slice objects.
Guido van Rossum's avatar
Guido van Rossum committed
5 6 7 8 9 10

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

/* 
11
Py_Ellipsis encodes the '...' rubber index token. It is similar to
Guido van Rossum's avatar
Guido van Rossum committed
12 13 14 15 16
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"
17
#include "structmember.h"
Guido van Rossum's avatar
Guido van Rossum committed
18 19

static PyObject *
20
ellipsis_repr(PyObject *op)
Guido van Rossum's avatar
Guido van Rossum committed
21
{
22
	return PyString_FromString("Ellipsis");
Guido van Rossum's avatar
Guido van Rossum committed
23 24
}

25
static PyTypeObject PyEllipsis_Type = {
Guido van Rossum's avatar
Guido van Rossum committed
26
	PyObject_HEAD_INIT(&PyType_Type)
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
	0,					/* ob_size */
	"ellipsis",				/* tp_name */
	0,					/* tp_basicsize */
	0,					/* tp_itemsize */
	0, /*never called*/			/* tp_dealloc */
	0,					/* tp_print */
	0,					/* tp_getattr */
	0,					/* tp_setattr */
	0,					/* tp_compare */
	(reprfunc)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 */
Guido van Rossum's avatar
Guido van Rossum committed
47 48
};

49 50
PyObject _Py_EllipsisObject = {
	PyObject_HEAD_INIT(&PyEllipsis_Type)
Guido van Rossum's avatar
Guido van Rossum committed
51 52 53 54 55 56 57 58 59 60
};


/* Slice object implementation

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

PyObject *
61
PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
Guido van Rossum's avatar
Guido van Rossum committed
62
{
63
	PySliceObject *obj = PyObject_New(PySliceObject, &PySlice_Type);
Guido van Rossum's avatar
Guido van Rossum committed
64

65 66 67
	if (obj == NULL)
		return NULL;

Guido van Rossum's avatar
Guido van Rossum committed
68 69 70 71 72 73 74 75 76 77 78 79 80 81 82
	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;

	return (PyObject *) obj;
}

int
83 84
PySlice_GetIndices(PySliceObject *r, int length,
                   int *start, int *stop, int *step)
Guido van Rossum's avatar
Guido van Rossum committed
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111
{
	if (r->step == Py_None) {
		*step = 1;
	} else {
		if (!PyInt_Check(r->step)) return -1;
		*step = PyInt_AsLong(r->step);
	}
	if (r->start == Py_None) {
		*start = *step < 0 ? length-1 : 0;
	} else {
		if (!PyInt_Check(r->start)) return -1;
		*start = PyInt_AsLong(r->start);
		if (*start < 0) *start += length;
	}
	if (r->stop == Py_None) {
		*stop = *step < 0 ? -1 : length;
	} else {
		if (!PyInt_Check(r->stop)) return -1;
		*stop = PyInt_AsLong(r->stop);
		if (*stop < 0) *stop += length;
	}
	if (*stop > length) return -1;
	if (*start >= length) return -1;
	if (*step == 0) return -1;
	return 0;
}

112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153
int
PySlice_GetIndicesEx(PySliceObject *r, int length,
		     int *start, int *stop, int *step, int *slicelength)
{
	/* this is harder to get right than you might think */
	int defstart, defstop;

	if (r->step == Py_None) {
		*step = 1;
	} else {
		*step = PyInt_AsLong(r->step);
		if (*step == -1 && PyErr_Occurred()) {
			return -1;
		}
		else if (*step == 0) {
			PyErr_SetString(PyExc_ValueError,
					"slice step cannot be zero");
			return -1;
		}
	}

	defstart = *step < 0 ? length-1 : 0;
	defstop = *step < 0 ? -1 : length;

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

	if (r->stop == Py_None) {
		*stop = defstop;
	} else {
		if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
		if (*stop < 0) *stop += length;
		if (*stop < 0) *stop = -1;
		if (*stop > length) *stop = length;
	}
154 155 156 157 158
	
	if ((*stop - *start)*(*step) <= 0) {
		*slicelength = 0;
	}
	else if (*step < 0) {
159 160 161 162 163 164 165 166
		*slicelength = (*stop-*start+1)/(*step)+1;
	} else {
		*slicelength = (*stop-*start-1)/(*step)+1;
	}

	return 0;
}

167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190
static PyObject *
slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
	PyObject *start, *stop, *step;

	start = stop = step = NULL;

	if (!PyArg_ParseTuple(args, "O|OO:slice", &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([start,] stop[, step])\n\
\n\
Create a slice object.  This is used for extended slicing (e.g. a[0:10:2]).");

Guido van Rossum's avatar
Guido van Rossum committed
191
static void
192
slice_dealloc(PySliceObject *r)
Guido van Rossum's avatar
Guido van Rossum committed
193 194 195 196
{
	Py_DECREF(r->step);
	Py_DECREF(r->start);
	Py_DECREF(r->stop);
197
	PyObject_Del(r);
Guido van Rossum's avatar
Guido van Rossum committed
198 199 200
}

static PyObject *
201
slice_repr(PySliceObject *r)
Guido van Rossum's avatar
Guido van Rossum committed
202 203 204 205 206 207 208 209 210 211 212 213 214 215 216
{
	PyObject *s, *comma;

	s = PyString_FromString("slice(");
	comma = PyString_FromString(", ");
	PyString_ConcatAndDel(&s, PyObject_Repr(r->start));
	PyString_Concat(&s, comma);
	PyString_ConcatAndDel(&s, PyObject_Repr(r->stop));
	PyString_Concat(&s, comma);
	PyString_ConcatAndDel(&s, PyObject_Repr(r->step));
	PyString_ConcatAndDel(&s, PyString_FromString(")"));
	Py_DECREF(comma);
	return s;
}

217
static PyMemberDef slice_members[] = {
218 219 220 221 222
	{"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
	{"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
	{"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
	{0}
};
Guido van Rossum's avatar
Guido van Rossum committed
223

224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243
static int
slice_compare(PySliceObject *v, PySliceObject *w)
{
	int result = 0;

        if (v == w)
		return 0;

	if (PyObject_Cmp(v->start, w->start, &result) < 0)
	    return -2;
	if (result != 0)
		return result;
	if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
	    return -2;
	if (result != 0)
		return result;
	if (PyObject_Cmp(v->step, w->step, &result) < 0)
	    return -2;
	return result;
}
Guido van Rossum's avatar
Guido van Rossum committed
244 245 246 247 248 249 250

PyTypeObject PySlice_Type = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,			/* Number of items for varobject */
	"slice",		/* Name of this type */
	sizeof(PySliceObject),	/* Basic object size */
	0,			/* Item size for varobject */
251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266
	(destructor)slice_dealloc,		/* tp_dealloc */
	0,					/* tp_print */
	0,					/* tp_getattr */
	0,					/* tp_setattr */
	(cmpfunc)slice_compare, 		/* tp_compare */
	(reprfunc)slice_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 */
267
	slice_doc,				/* tp_doc */
268 269 270 271 272 273 274 275 276 277 278
	0,					/* tp_traverse */
	0,					/* tp_clear */
	0,					/* tp_richcompare */
	0,					/* tp_weaklistoffset */
	0,					/* tp_iter */
	0,					/* tp_iternext */
	0,					/* tp_methods */
	slice_members,				/* tp_members */
	0,					/* tp_getset */
	0,					/* tp_base */
	0,					/* tp_dict */
279 280 281 282 283 284
	0,					/* tp_descr_get */
	0,					/* tp_descr_set */
	0,					/* tp_dictoffset */
	0,					/* tp_init */
	0,					/* tp_alloc */
	slice_new,				/* tp_new */
Guido van Rossum's avatar
Guido van Rossum committed
285
};