python/Objects/rangeobject.c at master · java66liu/python · GitHub

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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->step);

}

static Py_ssize_t

range_length(rangeobject *r)

{

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;

}

/* Pickling support */

static PyObject *

range_reduce(rangeobject *r, PyObject *args)

{

return Py_BuildValue("(O(iii))", Py_TYPE(r),

r->start,

r->start + r->len * r->step,

r->step);

}

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},

{"__reduce__", (PyCFunction)range_reduce, METH_VARARGS},

{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 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 */

};

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;

}

python/Objects/rangeobject.c at master · java66liu/python · GitHub

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