source: trunk/essentials/dev-lang/python/Objects/iterobject.c

/* Iterator objects */

#include "Python.h"

typedef struct {
        PyObject_HEAD
        long      it_index;
        PyObject *it_seq; /* Set to NULL when iterator is exhausted */
} seqiterobject;

PyObject *
PySeqIter_New(PyObject *seq)
{
        seqiterobject *it;

        if (!PySequence_Check(seq)) {
                PyErr_BadInternalCall();
                return NULL;
        }       
        it = PyObject_GC_New(seqiterobject, &PySeqIter_Type);
        if (it == NULL)
                return NULL;
        it->it_index = 0;
        Py_INCREF(seq);
        it->it_seq = seq;
        _PyObject_GC_TRACK(it);
        return (PyObject *)it;
}

static void
iter_dealloc(seqiterobject *it)
{
        _PyObject_GC_UNTRACK(it);
        Py_XDECREF(it->it_seq);
        PyObject_GC_Del(it);
}

static int
iter_traverse(seqiterobject *it, visitproc visit, void *arg)
{
        Py_VISIT(it->it_seq);
        return 0;
}

static PyObject *
iter_iternext(PyObject *iterator)
{
        seqiterobject *it;
        PyObject *seq;
        PyObject *result;

        assert(PySeqIter_Check(iterator));
        it = (seqiterobject *)iterator;
        seq = it->it_seq;
        if (seq == NULL)
                return NULL;

        result = PySequence_GetItem(seq, it->it_index);
        if (result != NULL) {
                it->it_index++;
                return result;
        }
        if (PyErr_ExceptionMatches(PyExc_IndexError) ||
            PyErr_ExceptionMatches(PyExc_StopIteration))
        {
                PyErr_Clear();
                Py_DECREF(seq);
                it->it_seq = NULL;
        }
        return NULL;
}

static PyObject *
iter_len(seqiterobject *it)
{
        Py_ssize_t seqsize, len;

        if (it->it_seq) {
                seqsize = PySequence_Size(it->it_seq);
                if (seqsize == -1)
                        return NULL;
                len = seqsize - it->it_index;
                if (len >= 0)
                        return PyInt_FromSsize_t(len);
        }
        return PyInt_FromLong(0);
}

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

static PyMethodDef seqiter_methods[] = {
        {"__length_hint__", (PyCFunction)iter_len, METH_NOARGS, length_hint_doc},
        {NULL,          NULL}           /* sentinel */
};

PyTypeObject PySeqIter_Type = {
        PyObject_HEAD_INIT(&PyType_Type)
        0,                                      /* ob_size */
        "iterator",                             /* tp_name */
        sizeof(seqiterobject),                  /* tp_basicsize */
        0,                                      /* tp_itemsize */
        /* methods */
        (destructor)iter_dealloc,               /* tp_dealloc */
        0,                                      /* tp_print */
        0,                                      /* tp_getattr */
        0,                                      /* tp_setattr */
        0,                                      /* tp_compare */
        0,                                      /* tp_repr */
        0,                                      /* tp_as_number */
        0,                                      /* tp_as_sequence */
        0,                                      /* tp_as_mapping */
        0,                                      /* tp_hash */
        0,                                      /* tp_call */
        0,                                      /* tp_str */
        PyObject_GenericGetAttr,                /* tp_getattro */
        0,                                      /* tp_setattro */
        0,                                      /* tp_as_buffer */
        Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
        0,                                      /* tp_doc */
        (traverseproc)iter_traverse,            /* tp_traverse */
        0,                                      /* tp_clear */
        0,                                      /* tp_richcompare */
        0,                                      /* tp_weaklistoffset */
        PyObject_SelfIter,                      /* tp_iter */
        iter_iternext,                          /* tp_iternext */
        seqiter_methods,                        /* tp_methods */
        0,                                      /* tp_members */
};

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

typedef struct {
        PyObject_HEAD
        PyObject *it_callable; /* Set to NULL when iterator is exhausted */
        PyObject *it_sentinel; /* Set to NULL when iterator is exhausted */
} calliterobject;

PyObject *
PyCallIter_New(PyObject *callable, PyObject *sentinel)
{
        calliterobject *it;
        it = PyObject_GC_New(calliterobject, &PyCallIter_Type);
        if (it == NULL)
                return NULL;
        Py_INCREF(callable);
        it->it_callable = callable;
        Py_INCREF(sentinel);
        it->it_sentinel = sentinel;
        _PyObject_GC_TRACK(it);
        return (PyObject *)it;
}
static void
calliter_dealloc(calliterobject *it)
{
        _PyObject_GC_UNTRACK(it);
        Py_XDECREF(it->it_callable);
        Py_XDECREF(it->it_sentinel);
        PyObject_GC_Del(it);
}

static int
calliter_traverse(calliterobject *it, visitproc visit, void *arg)
{
        Py_VISIT(it->it_callable);
        Py_VISIT(it->it_sentinel);
        return 0;
}

static PyObject *
calliter_iternext(calliterobject *it)
{
        if (it->it_callable != NULL) {
                PyObject *args = PyTuple_New(0);