cpython/Objects/rangeobject.c at doc-link-https · 180909/cpython · GitHub

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/* Range object implementation */

#include "Python.h"

#include "pycore_abstract.h" // _PyIndex_Check()

#include "pycore_range.h"

#include "pycore_long.h" // _PyLong_GetZero()

#include "pycore_tuple.h" // _PyTuple_ITEMS()

#include "structmember.h" // PyMemberDef

/* Support objects whose length is > PY_SSIZE_T_MAX.

This could be sped up for small PyLongs if they fit in a Py_ssize_t.

This only matters on Win64. Though we could use long long which

would presumably help perf.

typedef struct {

PyObject_HEAD

PyObject *start;

PyObject *stop;

PyObject *step;

PyObject *length;

} rangeobject;

/* Helper function for validating step. Always returns a new reference or

NULL on error.

static PyObject *

validate_step(PyObject *step)

{

/* No step specified, use a step of 1. */

if (!step)

return PyLong_FromLong(1);

step = PyNumber_Index(step);

if (step && _PyLong_Sign(step) == 0) {

PyErr_SetString(PyExc_ValueError,

"range() arg 3 must not be zero");

Py_CLEAR(step);

}

return step;

}

static PyObject *

compute_range_length(PyObject *start, PyObject *stop, PyObject *step);

static rangeobject *

make_range_object(PyTypeObject *type, PyObject *start,

PyObject *stop, PyObject *step)

{

rangeobject *obj = NULL;

PyObject *length;

length = compute_range_length(start, stop, step);

if (length == NULL) {

return NULL;

}

obj = PyObject_New(rangeobject, type);

if (obj == NULL) {

Py_DECREF(length);

return NULL;

}

obj->start = start;

obj->stop = stop;

obj->step = step;

obj->length = length;

return obj;

}

/* XXX(nnorwitz): should we error check if the user passes any empty ranges?

range(-10)

range(0, -5)

range(0, 5, -1)

static PyObject *

range_from_array(PyTypeObject *type, PyObject *const *args, Py_ssize_t num_args)

{

rangeobject *obj;

PyObject *start = NULL, *stop = NULL, *step = NULL;

switch (num_args) {

case 3:

step = args[2];

/* fallthrough */

case 2:

/* Convert borrowed refs to owned refs */

start = PyNumber_Index(args[0]);

if (!start) {

return NULL;

}

stop = PyNumber_Index(args[1]);

if (!stop) {

Py_DECREF(start);

return NULL;

}

step = validate_step(step); /* Caution, this can clear exceptions */

if (!step) {

Py_DECREF(start);

Py_DECREF(stop);

return NULL;

}

break;

case 1:

stop = PyNumber_Index(args[0]);

if (!stop) {

return NULL;

}

start = _PyLong_GetZero();

Py_INCREF(start);

step = _PyLong_GetOne();

Py_INCREF(step);

break;

case 0:

PyErr_SetString(PyExc_TypeError,

"range expected at least 1 argument, got 0");

return NULL;

default:

PyErr_Format(PyExc_TypeError,

"range expected at most 3 arguments, got %zd",

num_args);

return NULL;

}

obj = make_range_object(type, start, stop, step);

if (obj != NULL) {

return (PyObject *) obj;

}

/* Failed to create object, release attributes */

Py_DECREF(start);

Py_DECREF(stop);

Py_DECREF(step);

return NULL;

}

static PyObject *

range_new(PyTypeObject *type, PyObject *args, PyObject *kw)

{

if (!_PyArg_NoKeywords("range", kw))

return NULL;

return range_from_array(type, _PyTuple_ITEMS(args), PyTuple_GET_SIZE(args));

}

static PyObject *

range_vectorcall(PyTypeObject *type, PyObject *const *args,

size_t nargsf, PyObject *kwnames)

{

Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);

if (!_PyArg_NoKwnames("range", kwnames)) {

return NULL;

}

return range_from_array(type, args, nargs);

}

PyDoc_STRVAR(range_doc,

"range(stop) -> range object\n\

range(start, stop[, step]) -> range object\n\

\n\

Return an object that produces a sequence of integers from start (inclusive)\n\

to stop (exclusive) by step. range(i, j) produces i, i+1, i+2, ..., j-1.\n\

start defaults to 0, and stop is omitted! range(4) produces 0, 1, 2, 3.\n\

These are exactly the valid indices for a list of 4 elements.\n\

When step is given, it specifies the increment (or decrement).");

static void

range_dealloc(rangeobject *r)

{

Py_DECREF(r->start);

Py_DECREF(r->stop);

Py_DECREF(r->step);

Py_DECREF(r->length);

PyObject_Free(r);

}

/* Return number of items in range (lo, hi, step) as a PyLong object,

* when arguments are PyLong objects. Arguments MUST return 1 with

* PyLong_Check(). Return NULL when there is an error.

static PyObject*

compute_range_length(PyObject *start, PyObject *stop, PyObject *step)

{

/* -------------------------------------------------------------

Algorithm is equal to that of get_len_of_range(), but it operates

on PyObjects (which are assumed to be PyLong objects).

---------------------------------------------------------------*/

int cmp_result;

PyObject *lo, *hi;

PyObject *diff = NULL;

PyObject *tmp1 = NULL, *tmp2 = NULL, *result;

/* holds sub-expression evaluations */

PyObject *zero = _PyLong_GetZero(); // borrowed reference

PyObject *one = _PyLong_GetOne(); // borrowed reference

cmp_result = PyObject_RichCompareBool(step, zero, Py_GT);

if (cmp_result == -1)

return NULL;

if (cmp_result == 1) {

lo = start;

hi = stop;

Py_INCREF(step);

} else {

lo = stop;

hi = start;

step = PyNumber_Negative(step);

if (!step)

return NULL;

}

/* if (lo >= hi), return length of 0. */

cmp_result = PyObject_RichCompareBool(lo, hi, Py_GE);

if (cmp_result != 0) {

Py_DECREF(step);

if (cmp_result < 0)

return NULL;

result = zero;

Py_INCREF(result);

return result;

}

if ((tmp1 = PyNumber_Subtract(hi, lo)) == NULL)

goto Fail;

if ((diff = PyNumber_Subtract(tmp1, one)) == NULL)

goto Fail;

if ((tmp2 = PyNumber_FloorDivide(diff, step)) == NULL)

goto Fail;

if ((result = PyNumber_Add(tmp2, one)) == NULL)

goto Fail;

Py_DECREF(tmp2);

Py_DECREF(diff);

Py_DECREF(step);

Py_DECREF(tmp1);

return result;

Fail:

Py_DECREF(step);

Py_XDECREF(tmp2);

Py_XDECREF(diff);

Py_XDECREF(tmp1);

return NULL;

}

static Py_ssize_t

range_length(rangeobject *r)

{

return PyLong_AsSsize_t(r->length);

}

static PyObject *

compute_item(rangeobject *r, PyObject *i)

{

PyObject *incr, *result;

/* PyLong equivalent to:

* return r->start + (i * r->step)

if (r->step == _PyLong_GetOne()) {

result = PyNumber_Add(r->start, i);

}

else {

incr = PyNumber_Multiply(i, r->step);

if (!incr) {

return NULL;

}

result = PyNumber_Add(r->start, incr);

Py_DECREF(incr);

}

return result;

}

static PyObject *

compute_range_item(rangeobject *r, PyObject *arg)

{

PyObject *zero = _PyLong_GetZero(); // borrowed reference

int cmp_result;

PyObject *i, *result;

/* PyLong equivalent to:

* if (arg < 0) {

* i = r->length + arg

* } else {

* i = arg

* }

cmp_result = PyObject_RichCompareBool(arg, zero, Py_LT);

if (cmp_result == -1) {

return NULL;

}

if (cmp_result == 1) {

i = PyNumber_Add(r->length, arg);

if (!i) {

return NULL;

}

} else {

i = arg;

Py_INCREF(i);

}

/* PyLong equivalent to:

* if (i < 0 || i >= r->length) {

* <report index out of bounds>

* }

cmp_result = PyObject_RichCompareBool(i, zero, Py_LT);

if (cmp_result == 0) {

cmp_result = PyObject_RichCompareBool(i, r->length, Py_GE);

}

if (cmp_result == -1) {

Py_DECREF(i);

return NULL;

}

if (cmp_result == 1) {

Py_DECREF(i);

PyErr_SetString(PyExc_IndexError,

"range object index out of range");

return NULL;

}

result = compute_item(r, i);

Py_DECREF(i);

return result;

}

static PyObject *

range_item(rangeobject *r, Py_ssize_t i)

{

PyObject *res, *arg = PyLong_FromSsize_t(i);

if (!arg) {

return NULL;

}

res = compute_range_item(r, arg);

Py_DECREF(arg);

return res;

}

static PyObject *

compute_slice(rangeobject *r, PyObject *_slice)

{

PySliceObject *slice = (PySliceObject *) _slice;

rangeobject *result;

PyObject *start = NULL, *stop = NULL, *step = NULL;

PyObject *substart = NULL, *substop = NULL, *substep = NULL;

int error;

error = _PySlice_GetLongIndices(slice, r->length, &start, &stop, &step);

if (error == -1)

return NULL;

substep = PyNumber_Multiply(r->step, step);

if (substep == NULL) goto fail;

Py_CLEAR(step);

substart = compute_item(r, start);

if (substart == NULL) goto fail;

Py_CLEAR(start);

substop = compute_item(r, stop);

if (substop == NULL) goto fail;

Py_CLEAR(stop);

result = make_range_object(Py_TYPE(r), substart, substop, substep);

if (result != NULL) {

return (PyObject *) result;

}

fail:

Py_XDECREF(start);

Py_XDECREF(stop);

Py_XDECREF(step);

Py_XDECREF(substart);

Py_XDECREF(substop);

Py_XDECREF(substep);

return NULL;

}

/* Assumes (PyLong_CheckExact(ob) || PyBool_Check(ob)) */

static int

range_contains_long(rangeobject *r, PyObject *ob)

{

PyObject *zero = _PyLong_GetZero(); // borrowed reference

int cmp1, cmp2, cmp3;

PyObject *tmp1 = NULL;

PyObject *tmp2 = NULL;

int result = -1;

/* Check if the value can possibly be in the range. */

cmp1 = PyObject_RichCompareBool(r->step, zero, Py_GT);

if (cmp1 == -1)

goto end;

if (cmp1 == 1) { /* positive steps: start <= ob < stop */

cmp2 = PyObject_RichCompareBool(r->start, ob, Py_LE);

cmp3 = PyObject_RichCompareBool(ob, r->stop, Py_LT);

}

else { /* negative steps: stop < ob <= start */

cmp2 = PyObject_RichCompareBool(ob, r->start, Py_LE);

cmp3 = PyObject_RichCompareBool(r->stop, ob, Py_LT);

}

if (cmp2 == -1 || cmp3 == -1) /* TypeError */

goto end;

if (cmp2 == 0 || cmp3 == 0) { /* ob outside of range */

result = 0;

goto end;

}

/* Check that the stride does not invalidate ob's membership. */

tmp1 = PyNumber_Subtract(ob, r->start);

if (tmp1 == NULL)

goto end;

tmp2 = PyNumber_Remainder(tmp1, r->step);

if (tmp2 == NULL)

goto end;

/* result = ((int(ob) - start) % step) == 0 */

result = PyObject_RichCompareBool(tmp2, zero, Py_EQ);

end:

Py_XDECREF(tmp1);

Py_XDECREF(tmp2);

return result;

}

static int

range_contains(rangeobject *r, PyObject *ob)

{

if (PyLong_CheckExact(ob) || PyBool_Check(ob))

return range_contains_long(r, ob);

return (int)_PySequence_IterSearch((PyObject*)r, ob,

PY_ITERSEARCH_CONTAINS);

}

/* Compare two range objects. Return 1 for equal, 0 for not equal

and -1 on error. The algorithm is roughly the C equivalent of

if r0 is r1:

return True

if len(r0) != len(r1):

return False

if not len(r0):

return True

if r0.start != r1.start:

return False

if len(r0) == 1:

return True

return r0.step == r1.step

static int

range_equals(rangeobject *r0, rangeobject *r1)

{

int cmp_result;

if (r0 == r1)

return 1;

cmp_result = PyObject_RichCompareBool(r0->length, r1->length, Py_EQ);

/* Return False or error to the caller. */

if (cmp_result != 1)

return cmp_result;

cmp_result = PyObject_Not(r0->length);

/* Return True or error to the caller. */

if (cmp_result != 0)

return cmp_result;

cmp_result = PyObject_RichCompareBool(r0->start, r1->start, Py_EQ);

/* Return False or error to the caller. */

if (cmp_result != 1)

return cmp_result;

cmp_result = PyObject_RichCompareBool(r0->length, _PyLong_GetOne(), Py_EQ);

/* Return True or error to the caller. */

if (cmp_result != 0)

return cmp_result;

return PyObject_RichCompareBool(r0->step, r1->step, Py_EQ);

}

static PyObject *

range_richcompare(PyObject *self, PyObject *other, int op)

{

int result;

if (!PyRange_Check(other))

Py_RETURN_NOTIMPLEMENTED;

switch (op) {

case Py_NE:

case Py_EQ:

result = range_equals((rangeobject*)self, (rangeobject*)other);

if (result == -1)

return NULL;

if (op == Py_NE)

result = !result;

if (result)

Py_RETURN_TRUE;

else

Py_RETURN_FALSE;

case Py_LE:

case Py_GE:

case Py_LT:

case Py_GT:

Py_RETURN_NOTIMPLEMENTED;

default:

PyErr_BadArgument();

return NULL;

}

/* Hash function for range objects. Rough C equivalent of

if not len(r):

return hash((len(r), None, None))

if len(r) == 1:

return hash((len(r), r.start, None))

return hash((len(r), r.start, r.step))

static Py_hash_t

range_hash(rangeobject *r)

{

PyObject *t;

Py_hash_t result = -1;

int cmp_result;

t = PyTuple_New(3);

if (!t)

return -1;

Py_INCREF(r->length);

PyTuple_SET_ITEM(t, 0, r->length);

cmp_result = PyObject_Not(r->length);

if (cmp_result == -1)

goto end;

if (cmp_result == 1) {

Py_INCREF(Py_None);

PyTuple_SET_ITEM(t, 1, Py_None);

PyTuple_SET_ITEM(t, 2, Py_None);

}

else {

Py_INCREF(r->start);

PyTuple_SET_ITEM(t, 1, r->start);

cmp_result = PyObject_RichCompareBool(r->length, _PyLong_GetOne(), Py_EQ);

if (cmp_result == -1)

goto end;

if (cmp_result == 1) {

Py_INCREF(Py_None);

PyTuple_SET_ITEM(t, 2, Py_None);

}

else {

Py_INCREF(r->step);

PyTuple_SET_ITEM(t, 2, r->step);

}

result = PyObject_Hash(t);

end:

Py_DECREF(t);

return result;

}

static PyObject *

range_count(rangeobject *r, PyObject *ob)

{

if (PyLong_CheckExact(ob) || PyBool_Check(ob)) {

int result = range_contains_long(r, ob);

if (result == -1)

return NULL;

return PyLong_FromLong(result);

} else {

Py_ssize_t count;

count = _PySequence_IterSearch((PyObject*)r, ob, PY_ITERSEARCH_COUNT);

if (count == -1)

return NULL;

return PyLong_FromSsize_t(count);

}

static PyObject *

range_index(rangeobject *r, PyObject *ob)

{

int contains;

if (!PyLong_CheckExact(ob) && !PyBool_Check(ob)) {

Py_ssize_t index;

index = _PySequence_IterSearch((PyObject*)r, ob, PY_ITERSEARCH_INDEX);

if (index == -1)

return NULL;

return PyLong_FromSsize_t(index);

}

contains = range_contains_long(r, ob);

if (contains == -1)

return NULL;

if (contains) {

PyObject *idx = PyNumber_Subtract(ob, r->start);

if (idx == NULL) {

return NULL;

}

if (r->step == _PyLong_GetOne()) {

return idx;

}

/* idx = (ob - r.start) // r.step */

PyObject *sidx = PyNumber_FloorDivide(idx, r->step);

Py_DECREF(idx);

return sidx;

}

/* object is not in the range */

PyErr_Format(PyExc_ValueError, "%R is not in range", ob);

return NULL;

}

static PySequenceMethods range_as_sequence = {

(lenfunc)range_length, /* sq_length */

0, /* sq_concat */

0, /* sq_repeat */

(ssizeargfunc)range_item, /* sq_item */

0, /* sq_slice */

0, /* sq_ass_item */

0, /* sq_ass_slice */

(objobjproc)range_contains, /* sq_contains */

};

static PyObject *

range_repr(rangeobject *r)

{

Py_ssize_t istep;

/* Check for special case values for printing. We don't always

need the step value. We don't care about overflow. */

istep = PyNumber_AsSsize_t(r->step, NULL);

if (istep == -1 && PyErr_Occurred()) {

assert(!PyErr_ExceptionMatches(PyExc_OverflowError));

return NULL;

}

if (istep == 1)

return PyUnicode_FromFormat("range(%R, %R)", r->start, r->stop);

else

return PyUnicode_FromFormat("range(%R, %R, %R)",

r->start, r->stop, r->step);

}

/* Pickling support */

static PyObject *

range_reduce(rangeobject *r, PyObject *args)

{

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

r->start, r->stop, r->step);

}

static PyObject *

range_subscript(rangeobject* self, PyObject* item)

{

if (_PyIndex_Check(item)) {

PyObject *i, *result;

i = PyNumber_Index(item);

if (!i)

return NULL;

result = compute_range_item(self, i);

Py_DECREF(i);

return result;

}

if (PySlice_Check(item)) {

return compute_slice(self, item);

}

PyErr_Format(PyExc_TypeError,

"range indices must be integers or slices, not %.200s",

Py_TYPE(item)->tp_name);

return NULL;

}

static PyMappingMethods range_as_mapping = {

(lenfunc)range_length, /* mp_length */

(binaryfunc)range_subscript, /* mp_subscript */

(objobjargproc)0, /* mp_ass_subscript */

};

static int

range_bool(rangeobject* self)

{

return PyObject_IsTrue(self->length);

}

static PyNumberMethods range_as_number = {

.nb_bool = (inquiry)range_bool,

};

static PyObject * range_iter(PyObject *seq);

static PyObject * range_reverse(PyObject *seq, PyObject *Py_UNUSED(ignored));

PyDoc_STRVAR(reverse_doc,

"Return a reverse iterator.");

PyDoc_STRVAR(count_doc,

"rangeobject.count(value) -> integer -- return number of occurrences of value");

PyDoc_STRVAR(index_doc,

"rangeobject.index(value) -> integer -- return index of value.\n"

"Raise ValueError if the value is not present.");

static PyMethodDef range_methods[] = {

{"__reversed__", range_reverse, METH_NOARGS, reverse_doc},

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

{"count", (PyCFunction)range_count, METH_O, count_doc},

{"index", (PyCFunction)range_index, METH_O, index_doc},

{NULL, NULL} /* sentinel */

};

static PyMemberDef range_members[] = {

{"start", T_OBJECT_EX, offsetof(rangeobject, start), READONLY},

{"stop", T_OBJECT_EX, offsetof(rangeobject, stop), READONLY},

{"step", T_OBJECT_EX, offsetof(rangeobject, step), READONLY},

{0}

};

PyTypeObject PyRange_Type = {

PyVarObject_HEAD_INIT(&PyType_Type, 0)

"range", /* Name of this type */

sizeof(rangeobject), /* Basic object size */

0, /* Item size for varobject */

(destructor)range_dealloc, /* tp_dealloc */

0, /* tp_vectorcall_offset */

0, /* tp_getattr */

0, /* tp_setattr */

0, /* tp_as_async */

(reprfunc)range_repr, /* tp_repr */

&range_as_number, /* tp_as_number */

&range_as_sequence, /* tp_as_sequence */

&range_as_mapping, /* tp_as_mapping */

(hashfunc)range_hash, /* tp_hash */

0, /* tp_call */

0, /* tp_str */

PyObject_GenericGetAttr, /* tp_getattro */

0, /* tp_setattro */

0, /* tp_as_buffer */

Py_TPFLAGS_DEFAULT | Py_TPFLAGS_SEQUENCE, /* tp_flags */

range_doc, /* tp_doc */

0, /* tp_traverse */

0, /* tp_clear */

range_richcompare, /* tp_richcompare */

0, /* tp_weaklistoffset */

range_iter, /* tp_iter */

0, /* tp_iternext */

range_methods, /* tp_methods */

range_members, /* 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 */

.tp_vectorcall = (vectorcallfunc)range_vectorcall

};

/*********************** range Iterator **************************/

/* There are 2 types of iterators, one for C longs, the other for

Python ints (ie, PyObjects). This should make iteration fast

in the normal case, but possible for any numeric value.

static PyObject *

rangeiter_next(_PyRangeIterObject *r)

{

if (r->index < r->len)

/* cast to unsigned to avoid possible signed overflow

in intermediate calculations. */

return PyLong_FromLong((long)(r->start +

(unsigned long)(r->index++) * r->step));

return NULL;

}

static PyObject *

rangeiter_len(_PyRangeIterObject *r, PyObject *Py_UNUSED(ignored))

{

return PyLong_FromLong(r->len - r->index);

}

PyDoc_STRVAR(length_hint_doc,

"Private method returning an estimate of len(list(it)).");

static PyObject *

rangeiter_reduce(_PyRangeIterObject *r, PyObject *Py_UNUSED(ignored))

{

PyObject *start=NULL, *stop=NULL, *step=NULL;

PyObject *range;

/* create a range object for pickling */

start = PyLong_FromLong(r->start);

if (start == NULL)

goto err;

stop = PyLong_FromLong(r->start + r->len * r->step);

if (stop == NULL)

goto err;

step = PyLong_FromLong(r->step);

if (step == NULL)

goto err;

range = (PyObject*)make_range_object(&PyRange_Type,

start, stop, step);

if (range == NULL)

goto err;

/* return the result */

return Py_BuildValue(

"N(N)l", _PyEval_GetBuiltin(&_Py_ID(iter)), range, r->index);

err:

Py_XDECREF(start);

Py_XDECREF(stop);

Py_XDECREF(step);

return NULL;

}

static PyObject *

rangeiter_setstate(_PyRangeIterObject *r, PyObject *state)

{

long index = PyLong_AsLong(state);

if (index == -1 && PyErr_Occurred())

return NULL;

/* silently clip the index value */

if (index < 0)

index = 0;

else if (index > r->len)

index = r->len; /* exhausted iterator */

r->index = index;

Py_RETURN_NONE;

}

PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");

PyDoc_STRVAR(setstate_doc, "Set state information for unpickling.");

static PyMethodDef rangeiter_methods[] = {

{"__length_hint__", (PyCFunction)rangeiter_len, METH_NOARGS,

length_hint_doc},

{"__reduce__", (PyCFunction)rangeiter_reduce, METH_NOARGS,

reduce_doc},

{"__setstate__", (PyCFunction)rangeiter_setstate, METH_O,

setstate_doc},

{NULL, NULL} /* sentinel */

};

PyTypeObject PyRangeIter_Type = {

PyVarObject_HEAD_INIT(&PyType_Type, 0)

"range_iterator", /* tp_name */

sizeof(_PyRangeIterObject), /* tp_basicsize */

0, /* tp_itemsize */

/* methods */

(destructor)PyObject_Del, /* tp_dealloc */

0, /* tp_vectorcall_offset */

0, /* tp_getattr */

0, /* tp_setattr */

0, /* tp_as_async */

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, /* tp_members */

};

/* Return number of items in range (lo, hi, step). step != 0

* required. The result always fits in an unsigned long.

static unsigned long

get_len_of_range(long lo, long hi, long step)

{

/* -------------------------------------------------------------

If step > 0 and lo >= hi, or step < 0 and lo <= hi, the range is empty.

Else for step > 0, 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. The analysis for step < 0

is similar.

---------------------------------------------------------------*/

assert(step != 0);

if (step > 0 && lo < hi)

return 1UL + (hi - 1UL - lo) / step;

else if (step < 0 && lo > hi)

return 1UL + (lo - 1UL - hi) / (0UL - step);

else

return 0UL;

}

/* Initialize a rangeiter object. If the length of the rangeiter object

is not representable as a C long, OverflowError is raised. */

static PyObject *

fast_range_iter(long start, long stop, long step, long len)

{

_PyRangeIterObject *it = PyObject_New(_PyRangeIterObject, &PyRangeIter_Type);

if (it == NULL)

return NULL;

it->start = start;

it->step = step;

it->len = len;

it->index = 0;

return (PyObject *)it;

}

typedef struct {

PyObject_HEAD

PyObject *index;

PyObject *start;

PyObject *step;

PyObject *len;

} longrangeiterobject;

static PyObject *

longrangeiter_len(longrangeiterobject *r, PyObject *no_args)

{

return PyNumber_Subtract(r->len, r->index);

}

static PyObject *

longrangeiter_reduce(longrangeiterobject *r, PyObject *Py_UNUSED(ignored))

{

PyObject *product, *stop=NULL;

PyObject *range;

/* create a range object for pickling. Must calculate the "stop" value */

product = PyNumber_Multiply(r->len, r->step);

if (product == NULL)

return NULL;

stop = PyNumber_Add(r->start, product);

Py_DECREF(product);

if (stop == NULL)

return NULL;

Py_INCREF(r->start);

Py_INCREF(r->step);

range = (PyObject*)make_range_object(&PyRange_Type,

r->start, stop, r->step);

if (range == NULL) {

Py_DECREF(r->start);

Py_DECREF(stop);

Py_DECREF(r->step);

return NULL;

}

/* return the result */

return Py_BuildValue(

"N(N)O", _PyEval_GetBuiltin(&_Py_ID(iter)), range, r->index);

}

static PyObject *

longrangeiter_setstate(longrangeiterobject *r, PyObject *state)

{

PyObject *zero = _PyLong_GetZero(); // borrowed reference

int cmp;

/* clip the value */

cmp = PyObject_RichCompareBool(state, zero, Py_LT);

if (cmp < 0)

return NULL;

if (cmp > 0) {

state = zero;

}

else {

cmp = PyObject_RichCompareBool(r->len, state, Py_LT);

if (cmp < 0)

return NULL;

if (cmp > 0)

state = r->len;

}

Py_INCREF(state);

Py_XSETREF(r->index, state);

Py_RETURN_NONE;

}

static PyMethodDef longrangeiter_methods[] = {

{"__length_hint__", (PyCFunction)longrangeiter_len, METH_NOARGS,

length_hint_doc},

{"__reduce__", (PyCFunction)longrangeiter_reduce, METH_NOARGS,

reduce_doc},

{"__setstate__", (PyCFunction)longrangeiter_setstate, METH_O,

setstate_doc},

{NULL, NULL} /* sentinel */

};

static void

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cpython/Objects/rangeobject.c at doc-link-https · 180909/cpython · GitHub

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