range: lean and mean

Objects/rangeobject.c

 /* Range object implementation */
 
 #include "Python.h"
 #include "structmember.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.
@@ skipping 103 matching lines @@
 
 static void
 range_dealloc(rangeobject *r)
 {
     Py_DECREF(r->start);
     Py_DECREF(r->stop);
     Py_DECREF(r->step);
     Py_DECREF(r->length);
     PyObject_Del(r);
 }
 

[GvR, 2008/05/03 05:04:35]

Hm. I didn't mean for you to delete the entire comment, just to clean it up. :-)

+/*Return number of items in range (lo, hi, step), when arguments are
+* PyLong objects. step > 0 required. Return a PyLong with the length.
+* Return NULL when there is an error.*/
 static PyObject *
 range_compute_length(PyObject *start, PyObject *stop, PyObject *step)
 {
     /* -------------------------------------------------------------
     Algorithm is equal to that of get_len_of_range(), but it operates
     on PyObjects (which are assumed to be PyLong or PyInt objects).
     ---------------------------------------------------------------*/
     int cmp_result, cmp_call;
     PyObject *lo, *hi;
     PyObject *diff = NULL;
@@ skipping 52 matching lines @@
 
   Fail:
     Py_XDECREF(tmp2);
     Py_XDECREF(diff);
     Py_XDECREF(step);
     Py_XDECREF(tmp1);
     Py_XDECREF(one);
     return NULL;
 }
 
-static PyObject *
-range_length_hint(rangeobject *r)
-{
-    Py_INCREF(r->length);
-    return r->length;
-}
-
-PyDoc_STRVAR(range_length_hint_doc,
-"__length_hint__() -> int\n"
-"Return a estimate of len(list(range)).");
+static Py_ssize_t
+range_length(rangeobject *r)
+{
+    return PyLong_AsSsize_t(r->length);
+}
 
 
 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. */
@@ skipping 15 matching lines @@
     {"step", T_OBJECT, offsetof(rangeobject, step), READONLY},
     {0}
 };
 
 static PyObject * range_iter(PyObject *seq);
 static PyObject * range_reverse(PyObject *seq);
 
 PyDoc_STRVAR(reverse_doc,
 "Returns a reverse iterator.");
 
+static PySequenceMethods range_as_sequence = {
+    (lenfunc)range_length,  /* sq_length */
+    0,                      /* sq_concat */
+    0,                      /* sq_repeat */
+    0,                      /* sq_item */
+    0,                      /* sq_slice */
+    0,                      /* sq_ass_item */
+    0,                      /* sq_ass_slice */
+    0,                      /* sq_contains */
+    0,                      /* sq_inplace_concat */
+    0,                      /* sq_inplace_repeat */
+};
+
 static PyMethodDef range_methods[] = {
     {"__reversed__",    (PyCFunction)range_reverse, METH_NOARGS,
         reverse_doc},
-    {"__length_hint__", (PyCFunction)range_length_hint, METH_NOARGS,
-        range_length_hint_doc},
     {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_compare */
         (reprfunc)range_repr,   /* tp_repr */
         0,                      /* tp_as_number */
-        0,                      /* tp_as_sequence */
+        &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 */
@@ skipping 283 matching lines @@
 
     /* 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);
 
     Py_INCREF(r->length);
     it->length = r->length;
     it->index = PyLong_FromLong(0);
-    if (!it->index)
+    if (it->index == NULL)
         goto create_failure;
 
     return (PyObject *)it;
 
 create_failure:
     Py_DECREF(it);
     return NULL;
 }
 
 static PyObject *
@@ skipping 72 matching lines @@
         return NULL;
     }
 
     return (PyObject *)it;
 
 create_failure:
     Py_XDECREF(len);
     PyObject_Del(it);
     return NULL;
 }