Rhino: optimization for NativeFunction.java
Date:
Mon, 07 May 2001 14:19:59 +0200
From:
Igor Bukanov <igor.bukanov@windriver.com>
Organization:
Wind River
To:
Norris Boyd <nboyd@atg.com>
Hi, Norris!
This is the first of 3 patches that are completly independent from each
other.
Currently in NativeFunction its name stored as the first element in the
names array. But this lead to creation of a single element array for
each FunctionObject and for each script function that does not have
arguments or variables. The attached patch splits NativeFunction names
into simple functionName and argNames arrays and adjust code elsewhere
accordingly. This patch can increase memory footprint for anonymous
script functions without arguments because it adds additional field to
each NativeFunction, but I do not think this is a case to worry about.
Regards, Igor
Date: Mon, 07 May 2001 14:25:34 +0200
From: Igor Bukanov <igor.bukanov@windriver.com>
Organization: Wind River
To: Norris Boyd <nboyd@atg.com>
The current code that implements execMethod/methodArity for IdFunction
support returns an arbitrary value for id that is not known. This is not
very good behavior because it may hide bugs in the id support and it
also does not allow to distinguish ids that are used for function from
ids used for properties like String.length.
To fix this I changed semantic of the methodArity method to return -1
for an unknown/non-method id and added code to throw an exception for
bad ids. This change requires to adjust all NativeSomething objects that
use IdScriptabl and after a release all such interface changes would be
no go, but is not a release yet, right?
I also eliminated the "IdFunction f" argument from
IdFunction.Master.methodArity and the tagId field from IdFunction. When
I wrote the initial code for IdFunction.java, I added that just to be
able to use same id number in a class that implements IdFunction.Master
and its descendants via checking idTag. But that does not work in
general because IdScriptable can use id for non-function fields as well
so to avoid id clashes another way should be used. For example, if
someone would like to extend NativeMath to support more functionality,
he can use:
class Math2: extends NativeMath {
private static idBase;
{
if (idBase == 0) idBase = super.getMaximumId();
}
public int methodArity(int methodId) {
switch (methodId - idBase) {
case Id_foo: return 2;
case Id_bar: return 3;
}
return super.methodArity(methodId);
}
public Object execMethod
(int methodId, IdFunction f,
Context cx, Scriptable scope, Scriptable thisObj, Object[] args)
throws JavaScriptException
{
switch (methodId - idBase) {
case Id_foo: return ...;
case Id_bar: return ...;
}
return super.execMethod(methodId, f, cx, scope, thisObj, args);
}
protected int getMaximumId() { return idBase + MAX_ID; }
protected String getIdName(int id) {
switch (id - idBase) {
case Id_foo: return "for";
case Id_bar: return "bar";
}
return super.getIdName(id);
}
...
private static final int
Id_foo = 1,
Id_bar = 2,
MAX_ID = 2;
etc.
Note that a simpler solution to make MAX_ID field public in NativeMath
and write in Math2:
private static final int
Id_foo = NativeMath.MAX_ID + 1,
Id_bar = NativeMath.MAX_ID + 2,
MAX_ID = NativeMath.MAX_ID + 2;
does not work because in this way adding any new id to NativeMath would
break binary compatibility with Math2.
Rhino: fix for race conditions in listeners code in Context.java
Date:
Mon, 07 May 2001 14:22:57 +0200
From:
Igor Bukanov <igor.bukanov@windriver.com>
Organization:
Wind River
To:
Norris Boyd <nboyd@atg.com>
The current code for listeners and contextListeners in Context.java is
not race condition free. If contextListeners Vector would be modified
during context event firing loops, the code can produce
index-out-of-bounds exception. The problem with listeners array is more
subbtle and comes from the fact that ListenerCollection.java uses code like:
for(Enumeration enum = getAllListeners();enum.hasMoreElements();) {
Object listener = enum.nextElement();
if(iface.isInstance(listener)) {
array.addElement(listener);
}
}
where getAllListeners() uses Vector.elements to get element enumeration.
But to work with such enumeration in a thread safe way, one has to
synchronized against Vector, otherwise between enum.hasMoreElements()
and enum.nextElement() the last element can be removed.
Initially I thought to fix ListenerCollection and use it for
contextListeners as well, but then I realized that in its current form
ListenerCollection is very inefficient (it produces too many objects
just to get simple array to fire events), so I wrote ListenerArray.java
and use it in Context.java. It makes life simpler and shrinks code as well.
js_SetProtoOrParent should always have used a condvar in addition to a lock.
- Fix bug 79129, assert-botch in js_AllocSlot (r/sr=jband, sr=shaver)
JS_INITIAL_NSLOTS is the minimum number of slots, js_FreeSlot guarantees it.
Subject:
rhino bug(s)
Date:
Mon, 30 Apr 2001 23:07:00 -0700
From:
Mike Dixon <MDixon@placeware.com>
To:
nboyd@atg.com
hi. i'm a happy rhino user, and just stumbled across what looks like a
pretty basic bug in the property stuff on ScriptableObject... (i'm running
1.5, but it looks like this code hasn't changed in CVS.) since it looks
like you're actively developing (even though it's been a while since
1.5...) i figured you might be interested -- apologies if i missed a more
formal bug reporting process...
the symptom was that i got a "Hashtable internal error" thrown from
getSlotToSet. reading the code, here's what i think could happen:
- create a new object (slots.length is initially 5)
- add 3 properties
- delete those 3 properties
(now count == 0, and slots[i] == REMOVED for 3 values of i)
- add 2 more properties
now assume that you're unlucky, and that these two hash to different values
than the first three; now you have 2 elements of slots[] containing real
slots, and the other three containing REMOVED.
now what happens when you try to create another slot? getSlotToSet is only
willing to put something in a null slot[], and you haven't got one, so you
get the internal error.
writing this message encouraged me to try to write a test case to reproduce
it, and in fact it's trivial:
js> x={}; x.a=x.b=x.c=1; delete x.a; delete x.b; delete x.c; x.d=x.e=1
1
js> x.whatever=1
(boom)
by the way, while reading the code i also noticed what looks like another,
less consequential bug: addSlot increments count before deciding to grow
the table, which is done with a recursive call, which will cause count to
be incremented again -- right? as far as i can tell, setting count too big
will only cause it to grow the table a little early next time, so it
doesn't really matter, but it looks wrong.
.mike.
remove jsdIContext and jsdIThreadstate interfaces
add TYPE_BOOLEAN to jsdIValue
update callback signatures to reflect the removal of jsdIContext and jsdIThreadstate
add errorHook and throwHook attributes to jsdIDebuggerService
remove jsdThreadState and jsdContext objects.
consolidate ExecutionHook and BreakpointHook callbacks
remove return value checking from all methods (xpconnect does this for us.)
validate integrity of jsdScript data to guard against calling into a destroyed script.
queue up script deletes that happen during the JS GC cycle, call them when GC finishes (bug 76979.)
don't NS_IF_ADDREF objects that we get using *::FromPtr()
add jsdScript::Invalidate()
