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cpython/Objects/rangeobject.c

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/* Range object implementation */
#include "Python.h"
typedef struct {
PyObject_HEAD
long start;
long step;
long len;
} rangeobject;
/* Return number of items in range/xrange (lo, hi, step). step > 0
* required. Return a value < 0 if & only if the true value is too
* large to fit in a signed long.
*/
static long
get_len_of_range(long lo, long hi, long step)
{
/* -------------------------------------------------------------
If lo >= hi, the range is empty.
Else if n values are in the range, the last one is
lo + (n-1)*step, which must be <= hi-1. Rearranging,
n <= (hi - lo - 1)/step + 1, so taking the floor of the RHS gives
the proper value. Since lo < hi in this case, hi-lo-1 >= 0, so
the RHS is non-negative and so truncation is the same as the
floor. Letting M be the largest positive long, the worst case
for the RHS numerator is hi=M, lo=-M-1, and then
hi-lo-1 = M-(-M-1)-1 = 2*M. Therefore unsigned long has enough
precision to compute the RHS exactly.
---------------------------------------------------------------*/
long n = 0;
if (lo < hi) {
unsigned long uhi = (unsigned long)hi;
unsigned long ulo = (unsigned long)lo;
unsigned long diff = uhi - ulo - 1;
n = (long)(diff / (unsigned long)step + 1);
}
return n;
}
static PyObject *
range_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
rangeobject *obj;
long ilow = 0, ihigh = 0, istep = 1;
long n;
if (!_PyArg_NoKeywords("xrange()", kw))
return NULL;
if (PyTuple_Size(args) <= 1) {
if (!PyArg_ParseTuple(args,
"l;xrange() requires 1-3 int arguments",
&ihigh))
return NULL;
}
else {
if (!PyArg_ParseTuple(args,
"ll|l;xrange() requires 1-3 int arguments",
&ilow, &ihigh, &istep))
return NULL;
}
if (istep == 0) {
PyErr_SetString(PyExc_ValueError, "xrange() arg 3 must not be zero");
return NULL;
}
if (istep > 0)
n = get_len_of_range(ilow, ihigh, istep);
else
n = get_len_of_range(ihigh, ilow, -istep);
if (n < 0) {
PyErr_SetString(PyExc_OverflowError,
"xrange() result has too many items");
return NULL;
}
obj = PyObject_New(rangeobject, &PyRange_Type);
if (obj == NULL)
return NULL;
obj->start = ilow;
obj->len = n;
obj->step = istep;
return (PyObject *) obj;
}
PyDoc_STRVAR(range_doc,
"xrange([start,] stop[, step]) -> xrange object\n\
\n\
Like range(), but instead of returning a list, returns an object that\n\
generates the numbers in the range on demand. For looping, this is \n\
slightly faster than range() and more memory efficient.");
static PyObject *
range_item(rangeobject *r, Py_ssize_t i)
{
if (i < 0 || i >= r->len) {
PyErr_SetString(PyExc_IndexError,
"xrange object index out of range");
return NULL;
}
return PyInt_FromSsize_t(r->start + (i % r->len) * r->step);
}
static Py_ssize_t
range_length(rangeobject *r)
{
#if LONG_MAX != INT_MAX /* XXX ssize_t_max */
if (r->len > INT_MAX) {
PyErr_SetString(PyExc_ValueError,
"xrange object size cannot be reported");
return -1;
}
#endif
return (Py_ssize_t)(r->len);
}
static PyObject *
range_repr(rangeobject *r)
{
PyObject *rtn;
if (r->start == 0 && r->step == 1)
rtn = PyString_FromFormat("xrange(%ld)",
r->start + r->len * r->step);
else if (r->step == 1)
rtn = PyString_FromFormat("xrange(%ld, %ld)",
r->start,
r->start + r->len * r->step);
else
rtn = PyString_FromFormat("xrange(%ld, %ld, %ld)",
r->start,
r->start + r->len * r->step,
r->step);
return rtn;
}
static PySequenceMethods range_as_sequence = {
(lenfunc)range_length, /* sq_length */
0, /* sq_concat */
0, /* sq_repeat */
(ssizeargfunc)range_item, /* sq_item */
0, /* sq_slice */
};
static PyObject * range_iter(PyObject *seq);
static PyObject * range_reverse(PyObject *seq);
PyDoc_STRVAR(reverse_doc,
"Returns a reverse iterator.");
static PyMethodDef range_methods[] = {
{"__reversed__", (PyCFunction)range_reverse, METH_NOARGS, reverse_doc},
{NULL, NULL} /* sentinel */
};
PyTypeObject PyRange_Type = {
PyObject_HEAD_INIT(&PyType_Type)
0, /* Number of items for varobject */
"xrange", /* Name of this type */
sizeof(rangeobject), /* Basic object size */
0, /* Item size for varobject */
(destructor)PyObject_Del, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
(reprfunc)range_repr, /* tp_repr */
0, /* tp_as_number */
&range_as_sequence, /* 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 */
range_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
range_iter, /* tp_iter */
0, /* tp_iternext */
range_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 */
range_new, /* tp_new */
};
/*********************** Xrange Iterator **************************/
typedef struct {
PyObject_HEAD
long index;
long start;
long step;
long len;
} rangeiterobject;
static PyTypeObject Pyrangeiter_Type;
static PyObject *
range_iter(PyObject *seq)
{
rangeiterobject *it;
if (!PyRange_Check(seq)) {
PyErr_BadInternalCall();
return NULL;
}
it = PyObject_New(rangeiterobject, &Pyrangeiter_Type);
if (it == NULL)
return NULL;
it->index = 0;
it->start = ((rangeobject *)seq)->start;
it->step = ((rangeobject *)seq)->step;
it->len = ((rangeobject *)seq)->len;
return (PyObject *)it;
}
static PyObject *
range_reverse(PyObject *seq)
{
rangeiterobject *it;
long start, step, len;
if (!PyRange_Check(seq)) {
PyErr_BadInternalCall();
return NULL;
}
it = PyObject_New(rangeiterobject, &Pyrangeiter_Type);
if (it == NULL)
return NULL;
start = ((rangeobject *)seq)->start;
step = ((rangeobject *)seq)->step;
len = ((rangeobject *)seq)->len;
it->index = 0;
it->start = start + (len-1) * step;
it->step = -step;
it->len = len;
return (PyObject *)it;
}
static PyObject *
rangeiter_next(rangeiterobject *r)
{
if (r->index < r->len)
return PyInt_FromLong(r->start + (r->index++) * r->step);
return NULL;
}
static PyObject *
rangeiter_len(rangeiterobject *r)
{
return PyInt_FromLong(r->len - r->index);
}
PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");
static PyMethodDef rangeiter_methods[] = {
{"__length_hint__", (PyCFunction)rangeiter_len, METH_NOARGS, length_hint_doc},
{NULL, NULL} /* sentinel */
};
static PyTypeObject Pyrangeiter_Type = {
PyObject_HEAD_INIT(&PyType_Type)
0, /* ob_size */
"rangeiterator", /* tp_name */
sizeof(rangeiterobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
(destructor)PyObject_Del, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
0, /* 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 */
PyObject_SelfIter, /* tp_iter */
(iternextfunc)rangeiter_next, /* tp_iternext */
rangeiter_methods, /* tp_methods */
0,
};
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