906 lines
27 KiB
C
906 lines
27 KiB
C
/* Range object implementation */
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#include "Python.h"
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/* Support objects whose length is > PY_SSIZE_T_MAX.
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This could be sped up for small PyLongs if they fit in an Py_ssize_t.
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This only matters on Win64. Though we could use PY_LONG_LONG which
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would presumably help perf.
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*/
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typedef struct {
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PyObject_HEAD
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PyObject *start;
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PyObject *stop;
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PyObject *step;
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} rangeobject;
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/* Helper function for validating step. Always returns a new reference or
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NULL on error.
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*/
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static PyObject *
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validate_step(PyObject *step)
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{
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/* No step specified, use a step of 1. */
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if (!step)
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return PyLong_FromLong(1);
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step = PyNumber_Index(step);
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if (step) {
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Py_ssize_t istep = PyNumber_AsSsize_t(step, NULL);
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if (istep == -1 && PyErr_Occurred()) {
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/* Ignore OverflowError, we know the value isn't 0. */
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PyErr_Clear();
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}
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else if (istep == 0) {
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PyErr_SetString(PyExc_ValueError,
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"range() arg 3 must not be zero");
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Py_CLEAR(step);
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}
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}
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return step;
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}
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/* XXX(nnorwitz): should we error check if the user passes any empty ranges?
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range(-10)
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range(0, -5)
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range(0, 5, -1)
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*/
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static PyObject *
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range_new(PyTypeObject *type, PyObject *args, PyObject *kw)
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{
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rangeobject *obj = NULL;
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PyObject *start = NULL, *stop = NULL, *step = NULL;
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if (!_PyArg_NoKeywords("range()", kw))
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return NULL;
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if (PyTuple_Size(args) <= 1) {
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if (!PyArg_UnpackTuple(args, "range", 1, 1, &stop))
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return NULL;
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stop = PyNumber_Index(stop);
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if (!stop)
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return NULL;
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start = PyLong_FromLong(0);
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if (!start) {
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Py_DECREF(stop);
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return NULL;
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}
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step = PyLong_FromLong(1);
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if (!step) {
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Py_DECREF(stop);
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Py_DECREF(start);
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return NULL;
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}
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}
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else {
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if (!PyArg_UnpackTuple(args, "range", 2, 3,
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&start, &stop, &step))
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return NULL;
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/* Convert borrowed refs to owned refs */
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start = PyNumber_Index(start);
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if (!start)
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return NULL;
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stop = PyNumber_Index(stop);
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if (!stop) {
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Py_DECREF(start);
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return NULL;
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}
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step = validate_step(step); /* Caution, this can clear exceptions */
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if (!step) {
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Py_DECREF(start);
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Py_DECREF(stop);
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return NULL;
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}
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}
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obj = PyObject_New(rangeobject, &PyRange_Type);
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if (obj == NULL)
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goto Fail;
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obj->start = start;
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obj->stop = stop;
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obj->step = step;
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return (PyObject *) obj;
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Fail:
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Py_XDECREF(start);
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Py_XDECREF(stop);
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Py_XDECREF(step);
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return NULL;
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}
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PyDoc_STRVAR(range_doc,
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"range([start,] stop[, step]) -> range object\n\
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\n\
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Returns an iterator that generates the numbers in the range on demand.");
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static void
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range_dealloc(rangeobject *r)
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{
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Py_DECREF(r->start);
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Py_DECREF(r->stop);
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Py_DECREF(r->step);
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PyObject_Del(r);
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}
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/* Return number of items in range (lo, hi, step) as a PyLong object,
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* when arguments are PyLong objects. Arguments MUST return 1 with
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* PyLong_Check(). Return NULL when there is an error.
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*/
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static PyObject*
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range_length_obj(rangeobject *r)
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{
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/* -------------------------------------------------------------
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Algorithm is equal to that of get_len_of_range(), but it operates
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on PyObjects (which are assumed to be PyLong objects).
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---------------------------------------------------------------*/
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int cmp_result;
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PyObject *lo, *hi;
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PyObject *step = NULL;
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PyObject *diff = NULL;
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PyObject *one = NULL;
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PyObject *tmp1 = NULL, *tmp2 = NULL, *result;
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/* holds sub-expression evaluations */
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PyObject *zero = PyLong_FromLong(0);
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if (zero == NULL)
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return NULL;
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cmp_result = PyObject_RichCompareBool(r->step, zero, Py_GT);
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Py_DECREF(zero);
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if (cmp_result == -1)
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return NULL;
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if (cmp_result == 1) {
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lo = r->start;
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hi = r->stop;
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step = r->step;
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Py_INCREF(step);
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} else {
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lo = r->stop;
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hi = r->start;
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step = PyNumber_Negative(r->step);
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if (!step)
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return NULL;
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}
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/* if (lo >= hi), return length of 0. */
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if (PyObject_RichCompareBool(lo, hi, Py_GE) == 1) {
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Py_XDECREF(step);
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return PyLong_FromLong(0);
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}
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if ((one = PyLong_FromLong(1L)) == NULL)
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goto Fail;
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if ((tmp1 = PyNumber_Subtract(hi, lo)) == NULL)
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goto Fail;
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if ((diff = PyNumber_Subtract(tmp1, one)) == NULL)
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goto Fail;
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if ((tmp2 = PyNumber_FloorDivide(diff, step)) == NULL)
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goto Fail;
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if ((result = PyNumber_Add(tmp2, one)) == NULL)
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goto Fail;
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Py_DECREF(tmp2);
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Py_DECREF(diff);
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Py_DECREF(step);
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Py_DECREF(tmp1);
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Py_DECREF(one);
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return result;
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Fail:
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Py_XDECREF(tmp2);
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Py_XDECREF(diff);
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Py_XDECREF(step);
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Py_XDECREF(tmp1);
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Py_XDECREF(one);
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return NULL;
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}
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static Py_ssize_t
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range_length(rangeobject *r)
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{
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PyObject *len = range_length_obj(r);
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Py_ssize_t result = -1;
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if (len) {
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result = PyLong_AsSsize_t(len);
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Py_DECREF(len);
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}
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return result;
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}
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/* range(...)[x] is necessary for: seq[:] = range(...) */
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static PyObject *
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range_item(rangeobject *r, Py_ssize_t i)
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{
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Py_ssize_t len = range_length(r);
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PyObject *rem, *incr, *result;
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/* XXX(nnorwitz): should negative indices be supported? */
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/* XXX(nnorwitz): should support range[x] where x > PY_SSIZE_T_MAX? */
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if (i < 0 || i >= len) {
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if (!PyErr_Occurred())
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PyErr_SetString(PyExc_IndexError,
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"range object index out of range");
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return NULL;
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}
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/* XXX(nnorwitz): optimize for short ints. */
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rem = PyLong_FromSsize_t(i);
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if (!rem)
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return NULL;
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incr = PyNumber_Multiply(rem, r->step);
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Py_DECREF(rem);
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if (!incr)
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return NULL;
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result = PyNumber_Add(r->start, incr);
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Py_DECREF(incr);
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return result;
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}
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static PyObject *
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range_repr(rangeobject *r)
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{
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Py_ssize_t istep;
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/* Check for special case values for printing. We don't always
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need the step value. We don't care about errors
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(it means overflow), so clear the errors. */
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istep = PyNumber_AsSsize_t(r->step, NULL);
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if (istep != 1 || (istep == -1 && PyErr_Occurred())) {
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PyErr_Clear();
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}
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if (istep == 1)
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return PyUnicode_FromFormat("range(%R, %R)", r->start, r->stop);
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else
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return PyUnicode_FromFormat("range(%R, %R, %R)",
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r->start, r->stop, r->step);
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}
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/* Pickling support */
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static PyObject *
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range_reduce(rangeobject *r, PyObject *args)
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{
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return Py_BuildValue("(O(OOO))", Py_TYPE(r),
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r->start, r->stop, r->step);
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}
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/* Assumes (PyLong_CheckExact(ob) || PyBool_Check(ob)) */
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static int
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range_contains_long(rangeobject *r, PyObject *ob)
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{
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int cmp1, cmp2, cmp3;
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PyObject *tmp1 = NULL;
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PyObject *tmp2 = NULL;
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PyObject *zero = NULL;
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int result = -1;
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zero = PyLong_FromLong(0);
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if (zero == NULL) /* MemoryError in int(0) */
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goto end;
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/* Check if the value can possibly be in the range. */
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cmp1 = PyObject_RichCompareBool(r->step, zero, Py_GT);
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if (cmp1 == -1)
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goto end;
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if (cmp1 == 1) { /* positive steps: start <= ob < stop */
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cmp2 = PyObject_RichCompareBool(r->start, ob, Py_LE);
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cmp3 = PyObject_RichCompareBool(ob, r->stop, Py_LT);
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}
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else { /* negative steps: stop < ob <= start */
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cmp2 = PyObject_RichCompareBool(ob, r->start, Py_LE);
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cmp3 = PyObject_RichCompareBool(r->stop, ob, Py_LT);
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}
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if (cmp2 == -1 || cmp3 == -1) /* TypeError */
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goto end;
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if (cmp2 == 0 || cmp3 == 0) { /* ob outside of range */
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result = 0;
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goto end;
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}
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/* Check that the stride does not invalidate ob's membership. */
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tmp1 = PyNumber_Subtract(ob, r->start);
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if (tmp1 == NULL)
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goto end;
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tmp2 = PyNumber_Remainder(tmp1, r->step);
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if (tmp2 == NULL)
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goto end;
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/* result = (int(ob) - start % step) == 0 */
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result = PyObject_RichCompareBool(tmp2, zero, Py_EQ);
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end:
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Py_XDECREF(tmp1);
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Py_XDECREF(tmp2);
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Py_XDECREF(zero);
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return result;
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}
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static int
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range_contains(rangeobject *r, PyObject *ob) {
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if (PyLong_CheckExact(ob) || PyBool_Check(ob))
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return range_contains_long(r, ob);
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return (int)_PySequence_IterSearch((PyObject*)r, ob,
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PY_ITERSEARCH_CONTAINS);
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}
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static PyObject *
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range_count(rangeobject *r, PyObject *ob)
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{
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if (PyLong_CheckExact(ob) || PyBool_Check(ob)) {
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if (range_contains_long(r, ob))
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Py_RETURN_TRUE;
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else
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Py_RETURN_FALSE;
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} else {
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Py_ssize_t count;
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count = _PySequence_IterSearch((PyObject*)r, ob, PY_ITERSEARCH_COUNT);
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if (count == -1)
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return NULL;
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return PyLong_FromSsize_t(count);
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}
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}
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static PyObject *
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range_index(rangeobject *r, PyObject *ob)
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{
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PyObject *idx, *tmp;
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int contains;
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PyObject *format_tuple, *err_string;
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static PyObject *err_format = NULL;
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if (!PyLong_CheckExact(ob) && !PyBool_Check(ob)) {
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Py_ssize_t index;
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index = _PySequence_IterSearch((PyObject*)r, ob, PY_ITERSEARCH_INDEX);
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if (index == -1)
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return NULL;
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return PyLong_FromSsize_t(index);
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}
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contains = range_contains_long(r, ob);
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if (contains == -1)
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return NULL;
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if (!contains)
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goto value_error;
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tmp = PyNumber_Subtract(ob, r->start);
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if (tmp == NULL)
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return NULL;
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/* idx = (ob - r.start) // r.step */
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idx = PyNumber_FloorDivide(tmp, r->step);
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Py_DECREF(tmp);
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return idx;
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value_error:
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/* object is not in the range */
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if (err_format == NULL) {
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err_format = PyUnicode_FromString("%r is not in range");
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if (err_format == NULL)
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return NULL;
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}
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format_tuple = PyTuple_Pack(1, ob);
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if (format_tuple == NULL)
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return NULL;
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err_string = PyUnicode_Format(err_format, format_tuple);
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Py_DECREF(format_tuple);
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if (err_string == NULL)
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return NULL;
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PyErr_SetObject(PyExc_ValueError, err_string);
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Py_DECREF(err_string);
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return NULL;
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}
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static PySequenceMethods range_as_sequence = {
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(lenfunc)range_length, /* sq_length */
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0, /* sq_concat */
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0, /* sq_repeat */
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(ssizeargfunc)range_item, /* sq_item */
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0, /* sq_slice */
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0, /* sq_ass_item */
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0, /* sq_ass_slice */
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(objobjproc)range_contains, /* sq_contains */
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};
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static PyObject * range_iter(PyObject *seq);
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static PyObject * range_reverse(PyObject *seq);
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PyDoc_STRVAR(reverse_doc,
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"Returns a reverse iterator.");
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PyDoc_STRVAR(count_doc,
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"rangeobject.count(value) -> integer -- return number of occurrences of value");
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PyDoc_STRVAR(index_doc,
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"rangeobject.index(value, [start, [stop]]) -> integer -- return index of value.\n"
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"Raises ValueError if the value is not present.");
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static PyMethodDef range_methods[] = {
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{"__reversed__", (PyCFunction)range_reverse, METH_NOARGS, reverse_doc},
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{"__reduce__", (PyCFunction)range_reduce, METH_VARARGS},
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{"count", (PyCFunction)range_count, METH_O, count_doc},
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{"index", (PyCFunction)range_index, METH_O, index_doc},
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{NULL, NULL} /* sentinel */
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};
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PyTypeObject PyRange_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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"range", /* Name of this type */
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sizeof(rangeobject), /* Basic object size */
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0, /* Item size for varobject */
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(destructor)range_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_reserved */
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(reprfunc)range_repr, /* tp_repr */
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0, /* tp_as_number */
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&range_as_sequence, /* tp_as_sequence */
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0, /* tp_as_mapping */
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0, /* tp_hash */
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0, /* tp_call */
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0, /* tp_str */
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PyObject_GenericGetAttr, /* tp_getattro */
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT, /* tp_flags */
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range_doc, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
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0, /* tp_richcompare */
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0, /* tp_weaklistoffset */
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range_iter, /* tp_iter */
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0, /* tp_iternext */
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range_methods, /* tp_methods */
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0, /* tp_members */
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0, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0, /* tp_alloc */
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range_new, /* tp_new */
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};
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/*********************** range Iterator **************************/
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/* There are 2 types of iterators, one for C longs, the other for
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Python longs (ie, PyObjects). This should make iteration fast
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in the normal case, but possible for any numeric value.
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*/
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typedef struct {
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PyObject_HEAD
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long index;
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long start;
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long step;
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long len;
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} rangeiterobject;
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static PyObject *
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rangeiter_next(rangeiterobject *r)
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{
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if (r->index < r->len)
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/* cast to unsigned to avoid possible signed overflow
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in intermediate calculations. */
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return PyLong_FromLong((long)(r->start +
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(unsigned long)(r->index++) * r->step));
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return NULL;
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}
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static PyObject *
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rangeiter_len(rangeiterobject *r)
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{
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return PyLong_FromLong(r->len - r->index);
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}
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typedef struct {
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PyObject_HEAD
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PyObject *index;
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PyObject *start;
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PyObject *step;
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PyObject *len;
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} longrangeiterobject;
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static PyObject *
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longrangeiter_len(longrangeiterobject *r, PyObject *no_args)
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{
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return PyNumber_Subtract(r->len, r->index);
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}
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static PyObject *rangeiter_new(PyTypeObject *, PyObject *args, PyObject *kw);
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PyDoc_STRVAR(length_hint_doc,
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"Private method returning an estimate of len(list(it)).");
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static PyMethodDef rangeiter_methods[] = {
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{"__length_hint__", (PyCFunction)rangeiter_len, METH_NOARGS,
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length_hint_doc},
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{NULL, NULL} /* sentinel */
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};
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PyTypeObject PyRangeIter_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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|
"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;
|
|
}
|