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cpython/Objects/rangeobject.c

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/* Range object implementation */
#include "Python.h"
/* Support objects whose length is > PY_SSIZE_T_MAX.
This could be sped up for small PyLongs if they fit in an Py_ssize_t.
This only matters on Win64. Though we could use PY_LONG_LONG which
would presumably help perf.
*/
typedef struct {
PyObject_HEAD
PyObject *start;
PyObject *stop;
PyObject *step;
} 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) {
Py_ssize_t istep = PyNumber_AsSsize_t(step, NULL);
if (istep == -1 && PyErr_Occurred()) {
/* Ignore OverflowError, we know the value isn't 0. */
PyErr_Clear();
}
else if (istep == 0) {
PyErr_SetString(PyExc_ValueError,
"range() arg 3 must not be zero");
Py_CLEAR(step);
}
}
return step;
}
/* 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_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
rangeobject *obj = NULL;
PyObject *start = NULL, *stop = NULL, *step = NULL;
if (!_PyArg_NoKeywords("range()", kw))
return NULL;
if (PyTuple_Size(args) <= 1) {
if (!PyArg_UnpackTuple(args, "range", 1, 1, &stop))
return NULL;
stop = PyNumber_Index(stop);
if (!stop)
return NULL;
start = PyLong_FromLong(0);
if (!start) {
Py_DECREF(stop);
return NULL;
}
step = PyLong_FromLong(1);
if (!step) {
Py_DECREF(stop);
Py_DECREF(start);
return NULL;
}
}
else {
if (!PyArg_UnpackTuple(args, "range", 2, 3,
&start, &stop, &step))
return NULL;
/* Convert borrowed refs to owned refs */
start = PyNumber_Index(start);
if (!start)
return NULL;
stop = PyNumber_Index(stop);
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;
}
}
obj = PyObject_New(rangeobject, &PyRange_Type);
if (obj == NULL)
goto Fail;
obj->start = start;
obj->stop = stop;
obj->step = step;
return (PyObject *) obj;
Fail:
Py_XDECREF(start);
Py_XDECREF(stop);
Py_XDECREF(step);
return NULL;
}
PyDoc_STRVAR(range_doc,
"range([start,] stop[, step]) -> range object\n\
\n\
Returns an iterator that generates the numbers in the range on demand.");
static void
range_dealloc(rangeobject *r)
{
Py_DECREF(r->start);
Py_DECREF(r->stop);
Py_DECREF(r->step);
PyObject_Del(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*
range_length_obj(rangeobject *r)
{
/* -------------------------------------------------------------
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 *step = NULL;
PyObject *diff = NULL;
PyObject *one = NULL;
PyObject *tmp1 = NULL, *tmp2 = NULL, *result;
/* holds sub-expression evaluations */
PyObject *zero = PyLong_FromLong(0);
if (zero == NULL)
return NULL;
cmp_result = PyObject_RichCompareBool(r->step, zero, Py_GT);
Py_DECREF(zero);
if (cmp_result == -1)
return NULL;
if (cmp_result == 1) {
lo = r->start;
hi = r->stop;
step = r->step;
Py_INCREF(step);
} else {
lo = r->stop;
hi = r->start;
step = PyNumber_Negative(r->step);
if (!step)
return NULL;
}
/* if (lo >= hi), return length of 0. */
if (PyObject_RichCompareBool(lo, hi, Py_GE) == 1) {
Py_XDECREF(step);
return PyLong_FromLong(0);
}
if ((one = PyLong_FromLong(1L)) == NULL)
goto Fail;
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);
Py_DECREF(one);
return result;
Fail:
Py_XDECREF(tmp2);
Py_XDECREF(diff);
Py_XDECREF(step);
Py_XDECREF(tmp1);
Py_XDECREF(one);
return NULL;
}
static Py_ssize_t
range_length(rangeobject *r)
{
PyObject *len = range_length_obj(r);
Py_ssize_t result = -1;
if (len) {
result = PyLong_AsSsize_t(len);
Py_DECREF(len);
}
return result;
}
/* range(...)[x] is necessary for: seq[:] = range(...) */
static PyObject *
range_item(rangeobject *r, Py_ssize_t i)
{
Py_ssize_t len = range_length(r);
PyObject *rem, *incr, *result;
/* XXX(nnorwitz): should negative indices be supported? */
/* XXX(nnorwitz): should support range[x] where x > PY_SSIZE_T_MAX? */
if (i < 0 || i >= len) {
if (!PyErr_Occurred())
PyErr_SetString(PyExc_IndexError,
"range object index out of range");
return NULL;
}
/* XXX(nnorwitz): optimize for short ints. */
rem = PyLong_FromSsize_t(i);
if (!rem)
return NULL;
incr = PyNumber_Multiply(rem, r->step);
Py_DECREF(rem);
if (!incr)
return NULL;
result = PyNumber_Add(r->start, incr);
Py_DECREF(incr);
return result;
}
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 errors
(it means overflow), so clear the errors. */
istep = PyNumber_AsSsize_t(r->step, NULL);
if (istep != 1 || (istep == -1 && PyErr_Occurred())) {
PyErr_Clear();
}
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 int
range_contains(rangeobject *r, PyObject *ob) {
if (PyLong_CheckExact(ob) || PyBool_Check(ob)) {
int cmp1, cmp2, cmp3;
PyObject *tmp1 = NULL;
PyObject *tmp2 = NULL;
PyObject *zero = NULL;
int result = -1;
zero = PyLong_FromLong(0);
if (zero == NULL) /* MemoryError in int(0) */
goto end;
/* 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);
Py_XDECREF(zero);
return result;
}
/* Fall back to iterative search. */
return (int)_PySequence_IterSearch((PyObject*)r, ob,
PY_ITERSEARCH_CONTAINS);
}
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_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 = {
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_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_reserved */
(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 */
};
/*********************** range Iterator **************************/
/* There are 2 types of iterators, one for C longs, the other for
Python longs (ie, PyObjects). This should make iteration fast
in the normal case, but possible for any numeric value.
*/
typedef struct {
PyObject_HEAD
long index;
long start;
long step;
long len;
} rangeiterobject;
static PyObject *
rangeiter_next(rangeiterobject *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(rangeiterobject *r)
{
return PyLong_FromLong(r->len - r->index);
}
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 *rangeiter_new(PyTypeObject *, PyObject *args, PyObject *kw);
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 */
};
PyTypeObject PyRangeIter_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"range_iterator", /* 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_reserved */
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 */
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 */
rangeiter_new, /* tp_new */
};
/* 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 *
int_range_iter(long start, long stop, long step)
{
rangeiterobject *it = PyObject_New(rangeiterobject, &PyRangeIter_Type);
unsigned long ulen;
if (it == NULL)
return NULL;
it->start = start;
it->step = step;
ulen = get_len_of_range(start, stop, step);
if (ulen > (unsigned long)LONG_MAX) {
Py_DECREF(it);
PyErr_SetString(PyExc_OverflowError,
"range too large to represent as a range_iterator");
return NULL;
}
it->len = (long)ulen;
it->index = 0;
return (PyObject *)it;
}
static PyObject *
rangeiter_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
long start, stop, step;
if (!_PyArg_NoKeywords("rangeiter()", kw))
return NULL;
if (!PyArg_ParseTuple(args, "lll;rangeiter() requires 3 int arguments",
&start, &stop, &step))
return NULL;
return int_range_iter(start, stop, step);
}
static PyMethodDef longrangeiter_methods[] = {
{"__length_hint__", (PyCFunction)longrangeiter_len, METH_NOARGS,
length_hint_doc},
{NULL, NULL} /* sentinel */
};
static void
longrangeiter_dealloc(longrangeiterobject *r)
{
Py_XDECREF(r->index);
Py_XDECREF(r->start);
Py_XDECREF(r->step);
Py_XDECREF(r->len);
PyObject_Del(r);
}
static PyObject *
longrangeiter_next(longrangeiterobject *r)
{
PyObject *one, *product, *new_index, *result;
if (PyObject_RichCompareBool(r->index, r->len, Py_LT) != 1)
return NULL;
one = PyLong_FromLong(1);
if (!one)
return NULL;
new_index = PyNumber_Add(r->index, one);
Py_DECREF(one);
if (!new_index)
return NULL;
product = PyNumber_Multiply(r->index, r->step);
if (!product) {
Py_DECREF(new_index);
return NULL;
}
result = PyNumber_Add(r->start, product);
Py_DECREF(product);
if (result) {
Py_DECREF(r->index);
r->index = new_index;
}
else {
Py_DECREF(new_index);
}
return result;
}
PyTypeObject PyLongRangeIter_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"longrange_iterator", /* tp_name */
sizeof(longrangeiterobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
(destructor)longrangeiter_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_reserved */
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)longrangeiter_next, /* tp_iternext */
longrangeiter_methods, /* tp_methods */
0,
};
static PyObject *
range_iter(PyObject *seq)
{
rangeobject *r = (rangeobject *)seq;
longrangeiterobject *it;
long lstart, lstop, lstep;
PyObject *int_it;
assert(PyRange_Check(seq));
/* If all three fields and the length convert to long, use the int
* version */
lstart = PyLong_AsLong(r->start);
if (lstart == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
lstop = PyLong_AsLong(r->stop);
if (lstop == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
lstep = PyLong_AsLong(r->step);
if (lstep == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
int_it = int_range_iter(lstart, lstop, lstep);
if (int_it == NULL && PyErr_ExceptionMatches(PyExc_OverflowError)) {
PyErr_Clear();
goto long_range;
}
return (PyObject *)int_it;
long_range:
it = PyObject_New(longrangeiterobject, &PyLongRangeIter_Type);
if (it == NULL)
return NULL;
/* Do all initialization here, so we can DECREF on failure. */
it->start = r->start;
it->step = r->step;
Py_INCREF(it->start);
Py_INCREF(it->step);
it->len = it->index = NULL;
it->len = range_length_obj(r);
if (!it->len)
goto create_failure;
it->index = PyLong_FromLong(0);
if (!it->index)
goto create_failure;
return (PyObject *)it;
create_failure:
Py_DECREF(it);
return NULL;
}
static PyObject *
range_reverse(PyObject *seq)
{
rangeobject *range = (rangeobject*) seq;
longrangeiterobject *it;
PyObject *one, *sum, *diff, *len = NULL, *product;
long lstart, lstop, lstep, new_start, new_stop;
unsigned long ulen;
assert(PyRange_Check(seq));
/* reversed(range(start, stop, step)) can be expressed as
range(start+(n-1)*step, start-step, -step), where n is the number of
integers in the range.
If each of start, stop, step, -step, start-step, and the length
of the iterator is representable as a C long, use the int
version. This excludes some cases where the reversed range is
representable as a range_iterator, but it's good enough for
common cases and it makes the checks simple. */
lstart = PyLong_AsLong(range->start);
if (lstart == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
lstop = PyLong_AsLong(range->stop);
if (lstop == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
lstep = PyLong_AsLong(range->step);
if (lstep == -1 && PyErr_Occurred()) {
PyErr_Clear();
goto long_range;
}
/* check for possible overflow of -lstep */
if (lstep == LONG_MIN)
goto long_range;
/* check for overflow of lstart - lstep:
for lstep > 0, need only check whether lstart - lstep < LONG_MIN.
for lstep < 0, need only check whether lstart - lstep > LONG_MAX
Rearrange these inequalities as:
lstart - LONG_MIN < lstep (lstep > 0)
LONG_MAX - lstart < -lstep (lstep < 0)
and compute both sides as unsigned longs, to avoid the
possibility of undefined behaviour due to signed overflow. */
if (lstep > 0) {
if ((unsigned long)lstart - LONG_MIN < (unsigned long)lstep)
goto long_range;
}
else {
if (LONG_MAX - (unsigned long)lstart < 0UL - lstep)
goto long_range;
}
ulen = get_len_of_range(lstart, lstop, lstep);
if (ulen > (unsigned long)LONG_MAX)
goto long_range;
new_stop = lstart - lstep;
new_start = (long)(new_stop + ulen * lstep);
return int_range_iter(new_start, new_stop, -lstep);
long_range:
it = PyObject_New(longrangeiterobject, &PyLongRangeIter_Type);
if (it == NULL)
return NULL;
/* start + (len - 1) * step */
len = range_length_obj(range);
if (!len)
goto create_failure;
/* Steal reference to len. */
it->len = len;
one = PyLong_FromLong(1);
if (!one)
goto create_failure;
diff = PyNumber_Subtract(len, one);
Py_DECREF(one);
if (!diff)
goto create_failure;
product = PyNumber_Multiply(diff, range->step);
Py_DECREF(diff);
if (!product)
goto create_failure;
sum = PyNumber_Add(range->start, product);
Py_DECREF(product);
it->start = sum;
if (!it->start)
goto create_failure;
it->step = PyNumber_Negative(range->step);
if (!it->step)
goto create_failure;
it->index = PyLong_FromLong(0);
if (!it->index)
goto create_failure;
return (PyObject *)it;
create_failure:
Py_DECREF(it);
return NULL;
}
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