363 lines
11 KiB
C
363 lines
11 KiB
C
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/*
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Written by Jim Hugunin and Chris Chase.
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This includes both the singular ellipsis object and slice objects.
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Guido, feel free to do whatever you want in the way of copyrights
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for this file.
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*/
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/*
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Py_Ellipsis encodes the '...' rubber index token. It is similar to
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the Py_NoneStruct in that there is no way to create other objects of
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this type and there is exactly one in existence.
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*/
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#include "Python.h"
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#include "structmember.h"
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static PyObject *
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ellipsis_repr(PyObject *op)
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{
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return PyString_FromString("Ellipsis");
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}
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PyTypeObject PyEllipsis_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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"ellipsis", /* tp_name */
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0, /* tp_basicsize */
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0, /* tp_itemsize */
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0, /*never called*/ /* 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_compare */
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ellipsis_repr, /* tp_repr */
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0, /* tp_as_number */
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0, /* 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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};
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PyObject _Py_EllipsisObject = {
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_PyObject_EXTRA_INIT
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1, &PyEllipsis_Type
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};
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/* Slice object implementation
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start, stop, and step are python objects with None indicating no
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index is present.
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*/
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PyObject *
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PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
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{
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PySliceObject *obj = PyObject_New(PySliceObject, &PySlice_Type);
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if (obj == NULL)
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return NULL;
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if (step == NULL) step = Py_None;
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Py_INCREF(step);
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if (start == NULL) start = Py_None;
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Py_INCREF(start);
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if (stop == NULL) stop = Py_None;
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Py_INCREF(stop);
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obj->step = step;
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obj->start = start;
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obj->stop = stop;
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return (PyObject *) obj;
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}
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PyObject *
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_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
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{
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PyObject *start, *end, *slice;
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start = PyInt_FromSsize_t(istart);
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if (!start)
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return NULL;
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end = PyInt_FromSsize_t(istop);
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if (!end) {
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Py_DECREF(start);
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return NULL;
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}
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slice = PySlice_New(start, end, NULL);
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Py_DECREF(start);
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Py_DECREF(end);
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return slice;
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}
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int
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PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
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Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
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{
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/* XXX support long ints */
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if (r->step == Py_None) {
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*step = 1;
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} else {
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if (!PyInt_Check(r->step) && !PyLong_Check(r->step)) return -1;
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*step = PyInt_AsSsize_t(r->step);
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}
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if (r->start == Py_None) {
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*start = *step < 0 ? length-1 : 0;
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} else {
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if (!PyInt_Check(r->start) && !PyLong_Check(r->step)) return -1;
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*start = PyInt_AsSsize_t(r->start);
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if (*start < 0) *start += length;
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}
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if (r->stop == Py_None) {
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*stop = *step < 0 ? -1 : length;
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} else {
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if (!PyInt_Check(r->stop) && !PyLong_Check(r->step)) return -1;
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*stop = PyInt_AsSsize_t(r->stop);
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if (*stop < 0) *stop += length;
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}
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if (*stop > length) return -1;
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if (*start >= length) return -1;
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if (*step == 0) return -1;
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return 0;
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}
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int
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PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length,
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Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)
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{
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/* this is harder to get right than you might think */
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Py_ssize_t defstart, defstop;
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if (r->step == Py_None) {
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*step = 1;
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}
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else {
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if (!_PyEval_SliceIndex(r->step, step)) return -1;
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if (*step == 0) {
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PyErr_SetString(PyExc_ValueError,
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"slice step cannot be zero");
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return -1;
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}
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}
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defstart = *step < 0 ? length-1 : 0;
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defstop = *step < 0 ? -1 : length;
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if (r->start == Py_None) {
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*start = defstart;
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}
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else {
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if (!_PyEval_SliceIndex(r->start, start)) return -1;
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if (*start < 0) *start += length;
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if (*start < 0) *start = (*step < 0) ? -1 : 0;
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if (*start >= length)
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*start = (*step < 0) ? length - 1 : length;
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}
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if (r->stop == Py_None) {
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*stop = defstop;
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}
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else {
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if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
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if (*stop < 0) *stop += length;
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if (*stop < 0) *stop = (*step < 0) ? -1 : 0;
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if (*stop >= length)
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*stop = (*step < 0) ? length - 1 : length;
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}
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if ((*step < 0 && *stop >= *start)
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|| (*step > 0 && *start >= *stop)) {
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*slicelength = 0;
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}
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else if (*step < 0) {
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*slicelength = (*stop-*start+1)/(*step)+1;
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}
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else {
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*slicelength = (*stop-*start-1)/(*step)+1;
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}
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return 0;
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}
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static PyObject *
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slice_new(PyTypeObject *type, PyObject *args, PyObject *kw)
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{
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PyObject *start, *stop, *step;
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start = stop = step = NULL;
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if (!_PyArg_NoKeywords("slice()", kw))
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return NULL;
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if (!PyArg_UnpackTuple(args, "slice", 1, 3, &start, &stop, &step))
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return NULL;
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/* This swapping of stop and start is to maintain similarity with
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range(). */
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if (stop == NULL) {
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stop = start;
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start = NULL;
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}
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return PySlice_New(start, stop, step);
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}
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PyDoc_STRVAR(slice_doc,
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"slice(stop)\n\
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slice(start, stop[, step])\n\
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\n\
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Create a slice object. This is used for extended slicing (e.g. a[0:10:2]).");
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static void
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slice_dealloc(PySliceObject *r)
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{
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Py_DECREF(r->step);
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Py_DECREF(r->start);
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Py_DECREF(r->stop);
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PyObject_Del(r);
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}
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static PyObject *
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slice_repr(PySliceObject *r)
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{
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PyObject *s, *comma;
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s = PyString_FromString("slice(");
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comma = PyString_FromString(", ");
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PyString_ConcatAndDel(&s, PyObject_Repr(r->start));
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PyString_Concat(&s, comma);
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PyString_ConcatAndDel(&s, PyObject_Repr(r->stop));
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PyString_Concat(&s, comma);
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PyString_ConcatAndDel(&s, PyObject_Repr(r->step));
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PyString_ConcatAndDel(&s, PyString_FromString(")"));
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Py_DECREF(comma);
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return s;
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}
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static PyMemberDef slice_members[] = {
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{"start", T_OBJECT, offsetof(PySliceObject, start), READONLY},
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{"stop", T_OBJECT, offsetof(PySliceObject, stop), READONLY},
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{"step", T_OBJECT, offsetof(PySliceObject, step), READONLY},
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{0}
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};
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static PyObject*
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slice_indices(PySliceObject* self, PyObject* len)
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{
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Py_ssize_t ilen, start, stop, step, slicelength;
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ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
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if (ilen == -1 && PyErr_Occurred()) {
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return NULL;
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}
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if (PySlice_GetIndicesEx(self, ilen, &start, &stop,
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&step, &slicelength) < 0) {
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return NULL;
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}
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return Py_BuildValue("(nnn)", start, stop, step);
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}
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PyDoc_STRVAR(slice_indices_doc,
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"S.indices(len) -> (start, stop, stride)\n\
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\n\
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Assuming a sequence of length len, calculate the start and stop\n\
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indices, and the stride length of the extended slice described by\n\
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S. Out of bounds indices are clipped in a manner consistent with the\n\
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handling of normal slices.");
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static PyObject *
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slice_reduce(PySliceObject* self)
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{
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return Py_BuildValue("O(OOO)", Py_TYPE(self), self->start, self->stop, self->step);
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}
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PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
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static PyMethodDef slice_methods[] = {
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{"indices", (PyCFunction)slice_indices,
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METH_O, slice_indices_doc},
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{"__reduce__", (PyCFunction)slice_reduce,
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METH_NOARGS, reduce_doc},
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{NULL, NULL}
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};
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static int
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slice_compare(PySliceObject *v, PySliceObject *w)
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{
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int result = 0;
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if (v == w)
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return 0;
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if (PyObject_Cmp(v->start, w->start, &result) < 0)
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return -2;
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if (result != 0)
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return result;
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if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
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return -2;
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if (result != 0)
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return result;
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if (PyObject_Cmp(v->step, w->step, &result) < 0)
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return -2;
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return result;
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}
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static long
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slice_hash(PySliceObject *v)
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{
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PyErr_SetString(PyExc_TypeError, "unhashable type");
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return -1L;
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}
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PyTypeObject PySlice_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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"slice", /* Name of this type */
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sizeof(PySliceObject), /* Basic object size */
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0, /* Item size for varobject */
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(destructor)slice_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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(cmpfunc)slice_compare, /* tp_compare */
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(reprfunc)slice_repr, /* tp_repr */
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0, /* tp_as_number */
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0, /* tp_as_sequence */
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0, /* tp_as_mapping */
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(hashfunc)slice_hash, /* 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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slice_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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0, /* tp_iter */
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0, /* tp_iternext */
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slice_methods, /* tp_methods */
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slice_members, /* 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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slice_new, /* tp_new */
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};
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