On Wed, Jun 06, 2001 at 07:34:15AM -0700, Guido van Rossum wrote:
> Update of /cvsroot/python/python/dist/src/Objects
> In directory usw-pr-cvs1:/tmp/cvs-serv17474
>
> Modified Files:
> Tag: descr-branch
> object.c
> Log Message:
> Add _PyObject_GetDictPtr() -- an internal API to get a pointer to
> where __dict__ is stored in an object. The simplest case is to add
> tp_dictoffset to the start of the object, but there are comlications:
> tp_flags may tell us that tp_dictoffset is not defined, or the offset
> may be negative: indexing from the end of the object, where
> tp_itemsize may have to be taken into account.
Why would you ever have a negative size in there? That seems like an
unnecessary "feature". The offsets are easily set up by the compiler as
positive values. (not even sure how you'd come up with a proper/valid
negative value)
Cheers,
-g
>
>
> Index: object.c
> ===================================================================
> RCS file: /cvsroot/python/python/dist/src/Objects/object.c,v
> retrieving revision 2.124.4.11
> retrieving revision 2.124.4.12
> diff -C2 -r2.124.4.11 -r2.124.4.12
> *** object.c 2001/06/06 14:27:54 2.124.4.11
> --- object.c 2001/06/06 14:34:13 2.124.4.12
> ***************
> *** 1074,1077 ****
> --- 1074,1111 ----
> }
>
> + /* Helper to get a pointer to an object's __dict__ slot, if any */
> +
> + PyObject **
> + _PyObject_GetDictPtr(PyObject *obj)
> + {
> + #define PTRSIZE (sizeof(PyObject *))
> +
> + long dictoffset;
> + PyTypeObject *tp = obj->ob_type;
> +
> + if (!(tp->tp_flags & Py_TPFLAGS_HAVE_CLASS))
> + return NULL;
> + dictoffset = tp->tp_dictoffset;
> + if (dictoffset == 0)
> + return NULL;
> + if (dictoffset < 0) {
> + dictoffset += tp->tp_basicsize;
> + assert(dictoffset > 0); /* Sanity check */
> + if (tp->tp_itemsize > 0) {
> + int n = ((PyVarObject *)obj)->ob_size;
> + if (n > 0) {
> + dictoffset += tp->tp_itemsize * n;
> + /* Round up, if necessary */
> + if (tp->tp_itemsize % PTRSIZE != 0) {
> + dictoffset += PTRSIZE - 1;
> + dictoffset /= PTRSIZE;
> + dictoffset *= PTRSIZE;
> + }
> + }
> + }
> + }
> + return (PyObject **) ((char *)obj + dictoffset);
> + }
> +
> /* Generic GetAttr functions - put these in your tp_[gs]etattro slot */
>
> ***************
> *** 1082,1086 ****
> PyObject *descr;
> descrgetfunc f;
> ! int dictoffset;
>
> if (tp->tp_dict == NULL) {
> --- 1116,1120 ----
> PyObject *descr;
> descrgetfunc f;
> ! PyObject **dictptr;
>
> if (tp->tp_dict == NULL) {
> ***************
> *** 1097,1103 ****
> }
>
> ! dictoffset = tp->tp_dictoffset;
> ! if (dictoffset != 0) {
> ! PyObject *dict = * (PyObject **) ((char *)obj + dictoffset);
> if (dict != NULL) {
> PyObject *res = PyDict_GetItem(dict, name);
> --- 1131,1137 ----
> }
>
> ! dictptr = _PyObject_GetDictPtr(obj);
> ! if (dictptr != NULL) {
> ! PyObject *dict = *dictptr;
> if (dict != NULL) {
> PyObject *res = PyDict_GetItem(dict, name);
> ***************
> *** 1129,1133 ****
> PyObject *descr;
> descrsetfunc f;
> ! int dictoffset;
>
> if (tp->tp_dict == NULL) {
> --- 1163,1167 ----
> PyObject *descr;
> descrsetfunc f;
> ! PyObject **dictptr;
>
> if (tp->tp_dict == NULL) {
> ***************
> *** 1143,1149 ****
> }
>
> ! dictoffset = tp->tp_dictoffset;
> ! if (dictoffset != 0) {
> ! PyObject **dictptr = (PyObject **) ((char *)obj + dictoffset);
> PyObject *dict = *dictptr;
> if (dict == NULL && value != NULL) {
> --- 1177,1182 ----
> }
>
> ! dictptr = _PyObject_GetDictPtr(obj);
> ! if (dictptr != NULL) {
> PyObject *dict = *dictptr;
> if (dict == NULL && value != NULL) {
>
>
> _______________________________________________
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> Python-checkins@python.org
> http://mail.python.org/mailman/listinfo/python-checkins
--
Greg Stein, http://www.lyra.org/
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