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Fix Issue 1045.

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Factor-out common calling code by simplifying the length_hint API.
Speed-up the function by caching the PyObject_String for the attribute lookup.
This commit is contained in:
Raymond Hettinger 2007-12-06 00:56:53 +00:00
parent 923ad7a948
commit 4e2f714031
5 changed files with 48 additions and 86 deletions
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72
Objects/abstract.c
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@ -82,29 +82,47 @@ PyObject_Length(PyObject *o)
}
#define PyObject_Length PyObject_Size
Py_ssize_t
_PyObject_LengthHint(PyObject *o)
{
Py_ssize_t rv = PyObject_Size(o);
if (rv != -1)
return rv;
if (PyErr_ExceptionMatches(PyExc_TypeError) ||
PyErr_ExceptionMatches(PyExc_AttributeError)) {
PyObject *err_type, *err_value, *err_tb, *ro;
PyErr_Fetch(&err_type, &err_value, &err_tb);
ro = PyObject_CallMethod(o, "__length_hint__", NULL);
if (ro != NULL) {
rv = PyInt_AsLong(ro);
Py_DECREF(ro);
Py_XDECREF(err_type);
Py_XDECREF(err_value);
Py_XDECREF(err_tb);
return rv;
}
PyErr_Restore(err_type, err_value, err_tb);
/* The length hint function returns a non-negative value from o.__len__()
or o.__length_hint__(). If those methods aren't found or return a negative
value, then the defaultvalue is returned. This function never fails.
Accordingly, it will mask exceptions raised in either method.
*/
Py_ssize_t
_PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
{
static PyObject *hintstrobj = NULL;
PyObject *ro;
Py_ssize_t rv;
/* try o.__len__() */
rv = PyObject_Size(o);
if (rv >= 0)
return rv;
if (PyErr_Occurred())
PyErr_Clear();
/* cache a hashed version of the attribute string */
if (hintstrobj == NULL) {
hintstrobj = PyString_InternFromString("__length_hint__");
if (hintstrobj == NULL)
goto defaultcase;
}
return -1;
/* try o.__length_hint__() */
ro = PyObject_CallMethodObjArgs(o, hintstrobj, NULL);
if (ro == NULL)
goto defaultcase;
rv = PyInt_AsLong(ro);
Py_DECREF(ro);
if (rv >= 0)
return rv;
defaultcase:
if (PyErr_Occurred())
PyErr_Clear();
return defaultvalue;
}
PyObject *
@ -1505,17 +1523,7 @@ PySequence_Tuple(PyObject *v)
return NULL;
/* Guess result size and allocate space. */
n = _PyObject_LengthHint(v);
if (n < 0) {
if (PyErr_Occurred()
&& !PyErr_ExceptionMatches(PyExc_TypeError)
&& !PyErr_ExceptionMatches(PyExc_AttributeError)) {
Py_DECREF(it);
return NULL;
}
PyErr_Clear();
n = 10; /* arbitrary */
}
n = _PyObject_LengthHint(v, 10);
result = PyTuple_New(n);
if (result == NULL)
goto Fail;