Mailing List Archive: C optimisations in cAccessControl.c

Andreas, you checked this in:

http://cvs.zope.org/Zope/lib/python/AccessControl/Attic/cAccessControl.c.diff?r1=1.20.2.10&r2=1.20.2.11&hideattic=0&only_with_tag=Zope-2_7-branch

Log: replaced check for 'aq_' with strncmp()

--- Zope/lib/python/AccessControl/Attic/cAccessControl.c 2004/08/07
17:15:48 1.20.2.10
+++ Zope/lib/python/AccessControl/Attic/cAccessControl.c 2004/12/11
12:17:03 1.20.2.11
@@ -794,7 +794,7 @@
if ( PyString_Check(name) || PyUnicode_Check(name) ) {
sname = PyString_AsString(name);
if (sname != NULL) {
- if (*sname == 'a' && sname[1]=='q' && sname[2]=='_') {
+ if (! strncmp(sname, "aq_", 3)) {
if (strcmp(sname,"aq_parent") != 0 &&
strcmp(sname,"aq_inner") != 0 &&
strcmp(sname,"aq_explicit") != 0) {

My understanding is that the original code is much faster and does
short-circuit evaluation. Why did you do this change ?

There is a comparable change in a later checkin that also was there for
speed:

--- Zope/lib/python/AccessControl/Attic/cAccessControl.c 2004/12/11
12:17:03 1.20.2.11
+++ Zope/lib/python/AccessControl/Attic/cAccessControl.c 2004/12/12
10:52:15 1.20.2.12
@@ -1630,18 +1631,18 @@
/* we support both the old "_d" (from the Python implementation)
and the new "__roles__"
*/
- if (name_s[0] == '_') {
- if (name_s[1] == '_') {
- if (strcmp(name_s,"__name__") == 0)
- result= self->__name__;
- else if (strcmp(name_s,"__roles__") == 0)
- result= self->__roles__;
- }
- else if (name_s[1] == 'p' && name_s[2] == 0)
- result= self->_p;
- else if (name_s[1] == 'd' && name_s[2] == 0)
- result= self->__roles__;
+
+ if (name_s) {
+ if (!strcmp(name_s, "__name__"))
+ result= self->__name__;
+ else if (! strcmp(name_s, "__roles__"))
+ result= self->__roles__;
+ else if (! strcmp(name_s, "_p"))
+ result= self->_p;
+ else if (! strcmp(name_s, "_d"))
+ result= self->__roles__;
}
+
if (result) {
Py_INCREF(result);
return result;

The if (name_s[0] == '_') ... does short-circuit the common case of an
attribute without '_' much faster than doing many string comparisons.

Also, when fixing the crash bug, you fixed the multiple calls to
PyString_AsString(name) in SecurityManager_setattro but left those in
SecurityManager_getattro.

The current diff is:
http://cvs.zope.org/Zope/lib/python/AccessControl/Attic/cAccessControl.c.diff?r1=text&tr1=1.20.2.10&r2=text&tr2=1.20.2.13&diff_format=h

I also noticed you haven't merged these changes to cAccessControl.c
(crash bugfix) into svn trunk.

Florent

--
Florent Guillaume, Nuxeo (Paris, France) CTO, Director of R&D
+33 1 40 33 71 59 http://nuxeo.com fg@nuxeo.com
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[Florent Guillaume, with several comments about recent changes to
cAccessControl.c]

Please check the current version. I just finished a series of
checkins for endcase correctness, and happened to restore speed hacks
as I went along. I think these addressed all the points you raised.

...
> I also noticed you haven't merged these changes to cAccessControl.c
> (crash bugfix) into svn trunk.

Which was a good thing, since they weren't ready for prime time
<wink>. I should note that I don't intend to port them (I'm not
"supposed to be" working on this at all).
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